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About

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Sat, 20 Jun 2015 14:02:37 +0200

My name is Bhavesh S. Gupta, and I am currently working as a Sr. Software Engineer at InvestisDigital. I am passionate about using technology to make people’s lives better, and I believe that OpenSource technology is the key to achieving this goal.

Programming has always been a hobby of mine, and I have always loved the challenge of solving complex problems with code. As a Full Stack Engineer, I have had the opportunity to work with a wide range of technologies, including NodeJS, ReactJS, MonogoDB, Redis, DocumentDB, DRUPAL CMS, StencilJS (Web components), Python, HTML5, CSS3, JavaScript, and JQuery.

Despite my experience, I am always learning and trying to improve my skills as a developer. I believe that staying up-to-date with the latest languages and technologies is essential in this field. Whenever I get the chance, I try my hand at learning new languages and technologies, as I believe this helps me become a better engineer.

Through this website, I hope to share my experiences and insights with others who share my passion for technology. Whether you are a beginner or an experienced programmer, I hope you will find something of value here. Thank you for visiting, and I look forward to sharing more with you!

Exploring Backend-as-a-Service (BaaS) Platforms for Faster Development!

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Wed, 30 Apr 2025 17:39:08 +0530

Backend-as-a-Service (BaaS) platforms provide ready-made backend infrastructure—such as authentication, databases, real-time data sync, and hosting—so developers can focus on building the core features of their applications without worrying about common backend tasks.

Recently, while exploring options to rebuild one of our platforms, we evaluated several popular BaaS offerings:

Amazon Web Services (AWS) Amplify (Amplify Backend includes hosting)
Supabase
Pocketbase (Still in beta phase)
Convex
Firebase

These platforms are excellent choices if you want to accelerate development and launch quickly, especially for MVPs or prototypes. They reduce the need for managing backend infrastructure and allow small teams or startups to focus on product innovation.

A notable point: except for AWS Amplify and Firebase, most of these platforms support self-hosting, which can be a big advantage if you want more control over your data and infrastructure or even try them on a local system.

However, there are trade-offs: You might have less granular control compared to building a custom backend. Vendor lock-in can be a concern, especially with fully managed services. Custom or complex backend logic might require workarounds or additional services. I’m curious to hear from the community:

Have you used any of these BaaS platforms?
Which ones do you prefer for MVPs versus production-ready apps?
How do you handle scaling or custom backend requirements?

Comments here: https://www.linkedin.com/feed/update/urn:li:activity:7320309686535176193/

This is a cross post from my linkedin!.

Resignation Etiquette

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Mon, 08 Feb 2021 20:50:32 +0530

One follow etiquette about several things in life but rarely people talk about resignation etiquette.

Internet is one of those tool in the world which is boon and curse to people depending upon how you use it. It is great tool to get different perspectives over any problems by reading, listening and watching. Recently I have been reading about Resignation etiquette, after reading I decided to write down my thoughts on it, such that it could be helpful to someone. PS: I am still a very novice writer so there are can be profound mistake here. I am still learning sill growing. You may or may not agree with what I say here please don’t take me wrong.

Standard time

I feel in corporate world two weeks is the standard time for any course of action. In this time frame, management can meet and talk about all general affairs, people’s management, decision about promotion/demotion. So for any action you should give at-least two weeks of time, rest depends upon your situation.

Discussing problem with your manager/line manager/MD/CEO

There are times people resign due to some small problems like designation, salary, type of work or such small things which are easily solvable from management. In this case it is always better to discuss these before giving resignation, after talking if the solution can not be achieve in standard time then you can go ahead with your resignation. But you should not give resignation without dicussing this smaller issue. Sometime it is right time to move to another company for your own goals and everything if thats the case it is okay to go ahead.

Your manager should not be surprise with your official resignation mail

Your immediate manager should not be surprise with your resignation mail. It is good practice to inform them informally once before sending it. What ever your relation would be they are still your manager and they should be informed informally.

Once you have send resignation you should not take it back

As it is said you should be a person of your word. You should not take back your resignation. If you are in an environment where the things you deserve or desire or problems you are solved after putting resignation then you should leave that place asap if someone can’t recognized your efforts while discussing it, they would continue to do so in future as well.

Do not let your friends/colleague know that you have resigned un-till it is officially declared

I am still skeptical about this but it feels after official when you have given resignation you should not talk with friends. Usually this is open topic and eventually everyone knows. When people start knowing about the it then you can inform your close colleague.

PS: Usually your friends from office are someone who would know about this but your close colleague wont.

Do Give Notice When Possible

Normally every company has their own notice period policy. It ranges from 1 to 3 months in India. Ideally you should serve atleast 2 weeks of notice period or it depends upon your company policy. There is always or in most cases a point in your job description about early release by paying some financial loss to your company this is usually related to your salary.

If you feel leaving early is something that cannot be avoided then you should go with that option.

Do not leave with hate

People tend to live company with hate, fights and bad words which is last thing you want to do where you have worked for so long. It is always good to leave on happy face, you should not complain about a person, manager or company itself find a polite words for the words you want to say.

Delete all personal files/emails from your office pc/laptop

Ideally in your office pc there should not be anything personal but over time when you have been a place for long term some things make space in your office pc. You should clear/delete all these before giving notice. Sometime this happens where a company would ask you to leave on same day when you give your resignation. You should be ready for that, In such situation what ever you are feeling you should leave with happy face.

Last but not the least, do not burn bridges. You may never know with whom you may work again in life so it is better to always end on positive note

The Coin Weight Problem

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Wed, 03 Feb 2021 11:06:14 +0530

The problem resolves around find which of the coin is uneven in weight of all other coins. Suppose there are around 8 coin out of them one is heavy/light then others and we have one scale where we can compare two things

This is an interesting another problem which I had found while dicussing with Vatsal a friend of mine, which was asked in his interview for some company.

Suppose out of eight we know that one of them is of higher weight then others. The simplest way to achieve the solution for this problem would be doing a binary search like approach where you would divide in two equal half check which side is higher then again divde in two equal half and then look for higher side where you can reach finally to a conclusion on which coin is higher

Same approach can be taken when one of coin is lighter then others. For eight coin it would take atleast 3 round for above solution.

Now to optimize the solution we can look into another approach. Here as in above we are sure that one of the coin is higher in weight then others. In this case we can do something like this. We can take two coin aside and equally divide rest 6 coins. Then we can compare three with other three. If weight of one of side is higher then we can discard all other coin then this three as we are aware that only one coin is of higher weight then other. Now we have three coins left. We can weight two of them, if one of side is higher then we have found then coin. If both are equal then the one which we didnt weigh is coin with higher weight.

Other secenario could be where when we had compare 3 - 3 coins on each side they would have been of equal weigh. In that case we can weigh left two coins and get which one is higher.

In above solution we have optimized it further such that instead of three operation we are doing just two opertation.

The intresting problem here would be when we would not be aware whether a coin is lighter or heavier. In that case how we can optimize it. Whose solution we can try to find may in another blog post.

The Fizzbuzz Problem 2

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Tue, 02 Feb 2021 08:56:01 +0530

Last time I had stopped optimizing this the problem more because we were having a discussion where string concatination is a costly opperation. So yesterday I was talking with Nishchay how can about the previous blog and other things at that point we started on optimizing this further avoiding string contactination as well.

In Competetive programming, this is optimize even further, where % modulo operation is replaced by addtion and subtraction. This approach is also dicussed in same video which was shared in previous post.

let c3=0
let c5=0
for (number = 1; number <= 100; number++) {
 c3++;
 c5++;
 var outcome = ""
 if(c3==3) {outcome += "fizz";c3=0}
 if(c5==5) {outcome += "buzz";c5=0}
 if(outcome) console.log(outcome)
 else console.log(number)
}

c3 = 0
c5 = 0
for number in range(1, 101):
 c3+=1
 c5+=1
 outcome = ""
 if(c3 == 3) :
 outcome += 'fizz'
 c3=0
 if(c5 == 5) :
 outcome += 'buzz'
 c5=0
 if(outcome != "") : print(outcome)
 else: print(number)

While discussion this approach, with Vijay and Anup there was discussion that string contactination is costly operation compared to modulo. And instead of going above approach last approach to the problem was much better.

So yesterday I and Nishchay were dicussing this problem and working on a solution where we could avoid string contactination as well. While doing I tried to combine all of the example from previous post and come up with something as below

let c3=0
let c5=0
for (number = 1; number <= 100; number++) {
 c3++;
 c5++;
 var outcome = ""
 if(c3==3 && c5==5) {console.log("fizzbuzz");c3=0;c5=0}
 else if(c3==3){ console.log("fizz"); c3=0}
 else if(c5==5){ console.log("buzz"); c5=0}
 else console.log(number)
}

c3 = 0
c5 = 0
for number in range(1, 101):
 c3+=1
 c5+=1
 if(c3 == 3 and c5 == 3): print('fizzbuzz')
 elif(c3 == 3): print('fizz')
 elif(c5 == 5): print('buzz')
 else: print(number)

While dicussing Nishchay pointed out that in this solution also we incrementing three times why not try to lower number of increments and addition and make it further optimize. Then we come up the below solution.

var c3 = 3;
var c5 = 5;
for(number = 1; number <=100; number++){
 if(number == c5 && number == c3){
 console.log("fizzbuzz");
 c3 += 3;
 c5 += 5;
 } else if(number == c3){
 console.log("fizz");
 c3 += 3;
 } else if(number == c5){
 console.log("buzz");
 c5 += 5;
 } else console.log(number);
}

c3 = 3
c5 = 5
for number in range(1, 101) :
 if (number == c3 and number == c5) :
 print('fizzbuzz')
 c3 += 3
 c5 += 5
 elif (number == c3) :
 print('fizz')
 c3 += 3
 elif(number == c5):
 print('buzz')
 c5 += 5
 else: print(number)

A small problem with task to optimize it help me to write two blog post :D. If we find more better approach then there might be a third post to cover that :D.

The Fizzbuzz Problem

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Sun, 31 Jan 2021 16:42:25 +0530

Recently I have been giving few interviews and I have faced this problem twice or thrice I guess where an interviewer asks me this problem.

The essence of problem goes like this, the task is to print 1 to N (In most cases N is 100), where if number is divisible by 3 you would print fizz, if its divisible by 5 you would print buzz, if its divisible by both then print fizzbuzz.

Lets see output when N is let say 15:

1
2
fizz
4
buzz
fizz
7
8
fizz
buzz
11
fizz
13
14
fizzbuzz

The problem seems very simple in nature but it is an interesting problem to try when you are learning a new language. As I have been giving interviews in Javascript and python I would try to put of solution in both language.

PS: Here I am considering N to be 100 ;)

for (number = 1; number <= 100; number++) {
 if(number % 3 == 0 && number % 5 == 0) console.log("fizzbuzz")
 else if(number % 3 == 0) console.log("fizz")
 else if(number % 5 == 0) console.log("buzz")
 else console.log(number)
}

for number in range(1, 101):
 if(number % 3 == 0 and number % 5 == 0): print('fizzbuzz')
 elif(number % 3 == 0): print('fizz')
 elif(number % 5 == 0): print('buzz')
 else: print(number)

Above solution are correct, but if we see it from optimizing prospective then it is not optimize. We are doing same operation multiple times i.e. we are taking modulo of 3 and 5 twice, first in common case then again in else if cases.

First step towards optimizing it could be as follows

for (number = 1; number <= 100; number++) {
 let modulo3 = number % 3 == 0
 let modulo5 = number % 5 == 0
 if(modulo3 && modulo5) console.log("fizzbuzz")
 else if(modulo3) console.log("fizz")
 else if(modulo5) console.log("buzz")
 else console.log(number)
}

for number in range(1, 101):
 modulo3 = number % 3 == 0
 modulo5 = number % 5 == 0
 if(modulo3 and modulo5): print('fizzbuzz')
 elif(modulo3): print('fizz')
 elif(modulo5): print('buzz')
 else: print(number)

How above approach is more optimize then previous one can be said by, In previous approach lets say number is 5, then there would 3 modulo operation would be runnning while in the newer approach for any case there would just two modulo operation and we are storing two number.

I recently learned this from Arnav also known as championswimmer. He was talking about same at this video on the youtube channel of Coding Blocks where he optimize it even more then this.

In above video he showed on of the way to optimize it even better with two modulo and single storage the example he had shown was in kotlin and it goes as follows.

fun main (){
 for (i in 1..100) {
 var d = ""
 if(i % 3 == 0) { d+= "fizz" }
 if(i % 5 == 0) { d+= "buzz" }
 if(d == "" ) {
 println(i)
 } else {
 println(d)
 }
 }
}

We can optimize our solution even better with above approach lets try that as well.

for (number = 1; number <= 100; number++) {
 let outcome = ""
 if(number % 3 == 0) outcome += "fizz"
 if(number % 5 == 0) outcome += "buzz"
 if(outcome) console.log(outcome)
 else console.log(number)
}

for number in range(1, 101):
 outcome = ""
 if(number % 3 == 0) : outcome += 'fizz'
 if(number % 5 == 0) : outcome += 'buzz'
 if(outcome != "") : print(outcome)
 else: print(number)

PS: There has been some newer development on optimizing code and the newer approach we took. I had a brief discussion with Vijay aka Punnysher and Anop aka manchurian/potato :D. There would be another update to this.

First and Last post of 2020

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Thu, 31 Dec 2020 23:11:46 +0530

2020

2020, has been amazing year by far. Have experience so much this year which is unbelievable. Although I have not written anything then these two lines. But this would a memorable year in lot of sense.

Cheers, Happy New Year everyone, Happy 2021

Convert Excel to Json

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Sat, 14 Sep 2019 19:54:55 +0530

Some time in our projects we need data in json files(mostly web projects). But collecting and managing data in json files is harder(At least this is what I feel) compared to excel. I had recently ran into a similar situation where I need some data. Data is going to be provided by a non-technical person/client. And there going to be several rounds of it.

So I was looking for options what can be done here, where I found several online tools which could be used for same. But I don’t want to use that because of course privacy. I don’t want to upload an excel file to a unknown application which would process it server side give me results.

My search ended upon this. I found this nodejs module which was supper easy to use which would read your excel file and return a json object. So I created a small nodejs project which help me achieving solution to the problem.

var parser = require('simple-excel-to-json')
var doc = parser.parseXls2Json('sample.xlsx', { isNested: true });
const fs = require('fs');
fs.writeFileSync("sample.json",JSON.stringify(doc[0], null, 2), function(err) {
 if(err) {
 console.log("There was an error!");
 return console.log(err);
 }
});

So here is a repository link to source code. To run this you would need nodejs in your system.

You would need to a npm install and node index.js to this working.

Another Attempt at Wag3

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Sun, 25 Aug 2019 16:57:46 +0530

Until now we had done as of following code. We would create couples of more functions which would help us in managing our application. As discussed earlier we would now we creating different directories and files present inside .git directory along with directory itself. More or less we would something like following directory structure after doing wag init

.git is the git directory itself, which contains:
- .git/objects/ : the object store, which we’ll introduce in the next section.
- .git/refs/ the reference store, which we’ll discuss . It contains two subdirectories, heads and tags.
- .git/HEAD, a reference to the current HEAD (more on that later!)
- .git/config, the repository’s configuration file.
- .git/description, the repository’s description file.

import sys
import argparse
import os

argparser = argparse.ArgumentParser(description="Another Content Tracker")
argsubparsers = argparser.add_subparsers(title="Commands", dest="command")
argsubparsers.required = True
argsp = argsubparsers.add_parser(
 "init", help="Initialize a new, empty repository.")
argsp.add_argument("path", metavar="directory", nargs="?",
 default=".", help="Where to create the repository.")


def main(argv=sys.argv[1:]):
 args = argparser.parse_args(argv)
 if args.command == "init":
 cmd_init(args)


def cmd_init(args):
 repo_create(args.path)


class GitRepository(object):
 """A git repository"""
 worktree = None
 gitdir = None

 def __init__(self, path, force=False):
 self.worktree = path
 self.gitdir = os.path.join(path, ".git")


def repo_create(path):
 """Create a new repository at path."""
 repo = GitRepository(path)
 # We check whether there exsits a path of worktree
 if os.path.exists(repo.worktree):
 # if path exsits its a directory or not
 if not os.path.isdir(repo.worktree):
 raise Exception("%s is not a directory!" % path)
 # if path exsits its empty or not
 if os.listdir(repo.worktree):
 raise Exception("%s is not empty!" % path)
 else:
 # Create directory as nothing exist with same path
 os.makedirs(repo.worktree)

Now let’s create function which would gives us path of directory after verifying that the directory exist and if it doesn’t it should gives us an error. We would also require mechanism to check whether we need to create the directory or not if it doesn’t exists.

def repo_dir(repo, *path, mkdir=False):
 # repo is for our GitRepository object as we want to work with repository.
 # *path is the path we want to check
 # mkdir to specify whether we want to create directory or not.

 # this function would give us path we want to check if it exist or not
 path = repo_path(repo, *path)

 # This would check whether path exists and if it does then it would check if it is a directory or not
 if os.path.exists(path):
 if (os.path.isdir(path)):
 return path
 else:
 raise Exception("Not a directory %s" % path)

 # This would check if we need to create directory as it doesn't exists
 if mkdir:
 os.makedirs(path)
 return path
 else:
 return None


def repo_path(repo, *path):
 # This would return us path under repository git directory
 return os.path.join(repo.gitdir, *path)

We have created another repo_path function which is gives us path based on our git directory. Now we would add for these in our repo_create()

def repo_create(path):
 """Create a new repository at path."""
 repo = GitRepository(path)
 # We check whether there exists a path of worktree
 if os.path.exists(repo.worktree):
 # if path exists its a directory or not
 if not os.path.isdir(repo.worktree):
 raise Exception("%s is not a directory!" % path)
 # if path exists its empty or not
 if os.listdir(repo.worktree):
 raise Exception("%s is not empty!" % path)
 else:
 # Create directory as nothing exist with same path
 os.makedirs(repo.worktree)
 repo_path(repo, "branches")

 assert(repo_dir(repo, "branches", mkdir=True))
 assert(repo_dir(repo, "objects", mkdir=True))
 assert(repo_dir(repo, "refs", "tags", mkdir=True))
 assert(repo_dir(repo, "refs", "heads", mkdir=True))

Above would create .git directory with braches, objects and refs directory with tags and heads under it. It would look as follows:

.git
- objects
- branches
- refs
  - tags
  - heads

Assert() helps us to identify that all these directories are created. If there is some issue and we return None from function it would show assertation error.

Besides directories there are few files which are also created when you do a git init, so those also needs to be created when we wag init. Those files are config, HEAD and description others too but for now we would concentrate on these three.

Now these files could be created anywhere and that directory may or may not exist so we would so let’s create a function which would create these directories if require. Also lets open description file and write “Unnamed repository; edit this file ‘description’ to name the repository.” into that. We need to change this in our repo_create function

def repo_create(path):
 """Create a new repository at path."""
 repo = GitRepository(path)
 # We check whether there exists a path of worktree
 if os.path.exists(repo.worktree):
 # if path exists its a directory or not
 if not os.path.isdir(repo.worktree):
 raise Exception("%s is not a directory!" % path)
 # if path exists its empty or not
 if os.listdir(repo.worktree):
 raise Exception("%s is not empty!" % path)
 else:
 # Create directory as nothing exist with same path
 os.makedirs(repo.worktree)
 repo_path(repo, "branches")

 assert(repo_dir(repo, "branches", mkdir=True))
 assert(repo_dir(repo, "objects", mkdir=True))
 assert(repo_dir(repo, "refs", "tags", mkdir=True))
 assert(repo_dir(repo, "refs", "heads", mkdir=True))

 with open(repo_file(repo, "description"), "w") as f:
 f.write("Unnamed repository; edit this file 'description' to name the repository.\n")

def repo_file(repo, *path, mkdir=False):
 if repo_dir(repo, *path[:-1], mkdir=mkdir):
 return repo_path(repo, *path)

For config file we would need to use config parser module which would create a config file in Microsoft’s INI format. So first let’s create a function which would create default config. We would need to import this module with below modules. In default config there are thing fields,

repositoryformatversion whose value we would set to 0, for more info visit here. Our program would be compatible with only 0 format version only
filemode whose value would be set to false, it disables tacking of file mode changes
bare whose value would be false. It indicates that this repository has a work. Git supports an optional worktree key which indicates location of the worktree, if not ..(parent repository)

All these keys are under core section so first we would add section and then set this config.

def repo_default_config():
 ret = configparser.ConfigParser()

 ret.add_section("core")
 ret.set("core", "repositoryformatversion", "0")
 ret.set("core", "filemode", "false")
 ret.set("core", "bare", "false")

 return ret

Now let’s update our repo_create function to create config and Head file.

def repo_create(path):
 """Create a new repository at path."""
 repo = GitRepository(path)
 # We check whether there exsits a path of worktree
 if os.path.exists(repo.worktree):
 # if path exsits its a directory or not
 if not os.path.isdir(repo.worktree):
 raise Exception("%s is not a directory!" % path)
 # if path exsits its empty or not
 if os.listdir(repo.worktree):
 raise Exception("%s is not empty!" % path)
 else:
 # Create directory as nothing exist with same path
 os.makedirs(repo.worktree)
 repo_path(repo, "branches")

 assert(repo_dir(repo, "branches", mkdir=True))
 assert(repo_dir(repo, "objects", mkdir=True))
 assert(repo_dir(repo, "refs", "tags", mkdir=True))
 assert(repo_dir(repo, "refs", "heads", mkdir=True))

 with open(repo_file(repo, "description"), "w") as f:
 f.write("Unnamed repository; edit this file 'description' to name the repository.\n")

 with open(repo_file(repo, "HEAD"), "w") as f:
 f.write("ref: refs/heads/master\n")

 with open(repo_file(repo, "config"), "w") as f:
 config = repo_default_config()
 config.write(f)

This would complete our init method. YAY

Another Attempt at Wag 2

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Sat, 24 Aug 2019 15:32:32 +0530

Last time we had created cmd_init(args) function. We add more functionality to cmd_init(args).

This was our code till last time.

import sys
import argparse

argparser = argparse.ArgumentParser(description="Another Content Tracker")
argsubparsers = argparser.add_subparsers(title="Commands", dest="command")
argsubparsers.required = True
argsp = argsubparsers.add_parser("init", help="Initialize a new, empty repository.")
argsp.add_argument("path", metavar="directory", nargs="?", default=".", help="Where to create the repository.")

def main(argv=sys.argv[1:]):
 args = argparser.parse_args(argv)
 if args.command == "init":
 cmd_init(args)


def cmd_init(args):
 print("Hello from init")

We had added an argument to your sub parser called path. If the value of path is not specified it would be ‘.’ current directory or it would whatever specified. This would help us

A repository in git is consisted to two things a work tree where we have our files are there for version control and the git directory i.e. .git directory where Git stores its own data. In regular practice our work tree is a regular directory and git directory is child of that directory. Git supports all cases also our program would work in this case only.

For any command we run related to git there would be in git repo. So we create an object which would help us manage things. We would be working with lot of files we need to import another python module os.

So let’s create a class call GitRepository who’s object would give us worktree directory and .git directory. Later when we would create other commands into our code we can use this to check whether we are executing commands on a valid repository or not.

class GitRepository(object):
 """A git repository"""

 worktree = None
 gitdir = None
 conf = None

 def __init__(self, path):
 self.worktree = path
 self.gitdir = os.path.join(path, ".git")

We would create another function for our init command called `repo_create(path)` which would take our path argument from init.

def cmd_init(args):
 repo_create(args.path)

def repo_create(path):
 """Create a new repository at path."""
 repo = GitRepository(path)
 print(repo.worktree, repo.gitdir)

Now when you ./wag init you would get something like . ./.git and if you do ./wag init test and you would get test test/.git. So this would help us in creating directories.

As we have worktree path and git directory path we can check if worktree exist, if it doesn’t then we can create a directory. This would be used for creating things with ./wag init test

def repo_create(path):
 """Create a new repository at path."""
 repo = GitRepository(path)
 if os.path.exists(repo.worktree): # We check whether there exists a path of worktree
 if not os.path.isdir(repo.worktree):# if path exists it is a directory or not
 raise Exception("%s is not a directory!" % path)
 if os.listdir(repo.worktree):# if path exsits its empty or not
 raise Exception("%s is not empty!" % path)
 else:
 os.makedirs(repo.worktree) # Create directory as nothing exist with same path

In wag, we would only allow to init git if already existing repository is empty otherwise we won’t. Now we need to create .git directory and other directories inside it.

Another Attempt to write a git

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Thu, 22 Aug 2019 20:50:56 +0530

Second Try

We would be trying to create a mini git clone from this tutorial. I aspect this to go long. In general git is awesome source code manager which is wieldy use.

So first we would be creating a lib file and executing file.

Let’s create a file called wag which would have following code.

#!/usr/bin/env python3

import libwag
libwag.main()

Then we would create another file which would be libwag.py with just a main function in it.

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def main():
 print ("Hello from libwag")

We would then make our wag file executable by shell chmod +x wag. Now you can run wag by

./wag

In output screen you would get “Hello from libwag”.

We would be using several inbuilt module which are available in python to achieve working things.

First we would be importing a module called argparse. As per docs of argparse, it is a parser for command-line options, arguments and sub-command.

We would be importing sys module for getting arguments passed to program.

Our write a git, would be command line application which would work similar to git. For example for initiating we do git init here we would do wag init.

Note: To understand things better it would be better(not required), if you read documentation of argparse and checkout tutorial given in documentation.

We’ll need to handle subcommands (as in git: init, commit, etc.) In argparse language, these are called “subparsers”. In our current program it would always take one subparsers. Our argument would get stored in a string name command. And based on this string we would call different functions which we would require for our program to work.

Note: We would need to add each parser/command to our subparser so that our parser can dected whether the command we are passing is valid or not.

After all of above our code would look like below:

import sys
import argparse

argparser = argparse.ArgumentParser(description="Another Content Tracker")
argsubparsers = argparser.add_subparsers(title="Commands", dest="command")
argsubparsers.required = True
argsp = argsubparsers.add_parser("init", help="Initialize a new, empty repository.")

def main(argv=sys.argv[1:]):
 args = argparser.parse_args(argv)
 print(args.command)
 print("Hello from libwag")

If you would try to run above code as ./wag init it would print init and “Hello from libwag”. We would have multiple commands so, we would write a control flow to call different functions we make.

To keep things consistent we would use same nomenclature to define our functions. In our main function we would use a control flow statement then call function as per requirement. We would need to define the function we are calling.

def main(argv=sys.argv[1:]):
 args = argparser.parse_args(argv)
 if args.command == "init":
 cmd_init(args)


def cmd_init(args):
 print("Hello from init")

Now when we would call init it would call our cmd_init(args) method and do things for now just print “Hello from init”.

As we know(“I just came to know this today.”) git init also takes path as an optional argument and if path is not passed it would initialize current directory, if path is passed it would create that repository if it doesn’t exists. And initialize repo with .git directory.

We would add argument to our init command. Where we had defined our init command we would be adding code for to add an argument.

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2

argsp = argsubparsers.add_parser("init", help="Initialize a new, empty repository.")
argsp.add_argument("path", metavar="directory", nargs="?", default=".", help="Where to create the repository.")

An attempt to Write Yourself a Git

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Mon, 19 Aug 2019 21:13:07 +0530

So I tried to follow wyag at here but I was not able to. This tutorial is great but I was not able follow it because may be I am not still not much clear with python and how it works. So after much thought I have decided that I would try to create my own blog post series where I would take learnings from wyag and try to do it in my way.

Our first step would be to create repository and write init function. And then we would see how we can follow along.

Learning python through pym 14-08-2019

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Wed, 14 Aug 2019 16:57:26 +0530

Day 4

PS: These are notes, there could be grammar error and spelling errors.

for loops

For loop over a list goes as follows:

>>> a = ['Fedora', 'is', 'powerful']
>>> for x in a:
... print(x)
...
# these ... are automatically created by python interpreter
Fedora
is
powerful

range() function

range function creates lists based on parameter passed in function``py

>>> list(range(1, 5)) # when two numbers are passed n,j List starts at n ends at j-1
 [1, 2, 3, 4]
>>> list(range(1, 15, 3)) # when three numbers are passed n,j,k. List starts at n ends at j after stepping at every k steps
[1, 4, 7, 10, 13]
>>> list(range(10)) # when only single number n is passed list starts from 0 and ends after n elements
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Continue statement

Just like break is use to break loop, continue is used to continue loop towards iteration without further execution A combined example.

#!/usr/bin/env python3
while True:
 n = int(input("Please enter an Integer: "))
 if n < 0:
 continue # this will take the execution back to the starting of the loop
 elif n == 0:
 break
 print("Square is ", n ** 2)
print("Goodbye")

Data Structures

Lists

Few other things with lists:

# to insert a new element in list
>>> a = [23, 45, 1, -3434, 43624356, 234]
>>> a.append(45)
>>> a
[23, 45, 1, -3434, 43624356, 234, 45]
# to inset at particular position we have to pass position along. First would be position then would be element
>>> a.insert(0, 1)
>>> a
[1, 23, 45, 1, -3434, 43624356, 234, 45]
# to count number of occurrences of a element
>>> a.count(45)

Same way we have .reverse, .remove using append we can append another list to existing list as a element of the list

>>> b = [45, 56, 90]
>>> a.append(b)
>>> a
[45, 43624356, -3434, 1, 45, 23, 1, 111, [45, 56, 90]]

There is another method call .extend which would add element of second list as element of new list

>>> a.extend(b) #To add the values of b not the b itself
>>> a
[45, 43624356, -3434, 1, 45, 23, 1, 111, [45, 56, 90], 45, 56, 90]
>>> a[-1] # here in a[n] value of n is -1 so it would give last element
90
# to remove element which was we would pass same list or sublist to remove it.
>>> a.remove(b)
>>> a
[45, 43624356, -3434, 1, 45, 23, 1, 111, 45, 56, 90]
# .sort is use to sort list if list is sortable means elements are comparable.
# del can also be used to delete a element from list
>>> del a[-1]
>>> a
[-3434, 1, 1, 23, 45, 45, 45, 56, 90, 111]

Using lists as stack and queue

Stacks work as LIFO(Last In First Out) and queue work on FIFO(First In First Out)

>>> a = [1, 2, 3, 4, 5, 6]
>>> a
[1, 2, 3, 4, 5, 6]
# for Lifo and fifo everything would be appended at the end of list we would use append.
>>> a.append(34)
>>> a
[1, 2, 3, 4, 5, 6, 34]
# while removing element we would remove using pop
# for removing element in lifo we would use .pop() without any parameter so that it would remove last element
>>> a.pop()
34
# for fifo or queue where oldest element is removed first we use .pop(0)
>>> a.pop(0)
1

Note: .pop removes element and return removed element while append just add element doesn’t returns anything

Learning python through pym 13-08-2019

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Tue, 13 Aug 2019 20:57:26 +0530

Day 3

PS: These are notes, there could be grammar error and spelling errors.

Last time we were just starting with If else, the control flow,

if-else , the control flow

Control flow is used when we need to do some decisive task

if, if else, if elif else statement

If statement is simple as it is other language

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2

if expression:
 do this

if expression:
 do this
else:
 do this

if expression:
 do this
elif expression:
 do this
else:
 do this

Things to note:

‘:’ is must
Indentation must be proper.
if value is going to be true or false check it directly in if or elif expression without comparison operators.

Looping

Looping is used whenever you need to do repetitive task with some condition

while loop

1
2
3

while condition:
 statement1
 statement2

while loop we execute until condition is meet.

generating fibonacci using while

#!/usr/bin/env python3
a, b = 0, 1
while b < 100:
 print(b)
 a, b = b, a + b

By default print always prints in new line. We can change end by pass it into print function something like print(b, end=' '). This would not print \n <- newline character after every print statement instead it would print space.

break

break is used to break at loop. It could be because some conditions matched or whatever could be the case.

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2

if term < 0.0001:
 break

This means if the value of term is less than 0.0001 then get out of the loop. If this statement is kept inside a loop.

Decorating prints

We can print space separator’s and character separators using print. We can multiply string or character with a number to print that n number of times. for example

print("-" * 50)
--------------------------------------------------
>>> print("*" * 10)
**********
>>> print("#" * 20)
####################
>>> print("--" * 20)
----------------------------------------
>>> print("-" * 40)
----------------------------------------

Draw the pattern

One of the question which has haunt several to be under-graduate students(some graduates too) is drawing given pattern. I remember people using space and print statement to print exact same 5 line pattern then fighting with teacher to say When did you say we had to take input :D. Moving ahead.

So patterns in python becomes easy(even for those student) suppose we want below pattern:

*****
 ****
 ***
 **
 *

In python what we do is we take an input say draw 5 lines. we would print two things number of spaces and stars. Need to decrease number of stars and increase number of space.

#!/usr/bin/env python3
row = int(input("Enter the number of rows: "))
n = row
while n >= 0:
 x = "*" * n
 # This would store 5 star at start into variable x and keep decrease as -1 at bottom
 y = " " * (row - n)
 # This would store spaces as row - n initially value of both is same of there would 0 spaces and then they would keep increasing
 print(y + x)
 # This would print first space then start for that iteration
 n -= 1

Lists

Lists is similar to arrays in js.

>>> a = [ 1, 342, 223, 'India', 'Fedora']
>>> a
[1, 342, 223, 'India', 'Fedora']
# nth element in list
>>> a[0]
1
>>> a[4]
'Fedora'
# -nth element in list, that is nth element from end of list
>>> a[-1]
'Fedora'
>>> a[-2]
'India'
# n:m would return from n to mth element to list not including mth element.
# we can either side as blank. which would consider start and end of list
>>> a[0:-1]
[1, 342, 223, 'India']
>>> a[2:-2]
[223]
>>> a[:-2]
[1, 342, 223]
# Below we are using two :: which would work as [n:e:k], from nth to eth element jumping k elements. So if n is 0 and k is 2 then first element would be 0th then 2nd then 4th. and so on.
>>> a[0::2]
[1, 223, 'Fedora']
# to check whether value exists in list we can use 'in' operator
>>> 1 in a
True
>>> 2 in a
False
# len would give length in a
>>> len(a)
3

To check list is empty or not we use following code.

if list_name: # This means the list is not empty
 pass
else: # This means the list is empty
 pass

Have continue from for loop tomorrow :)

Learning python through pym 12-08-2019

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Mon, 12 Aug 2019 20:57:26 +0530

Day 2

PS: These are notes, there could be grammar error and spelling errors.

Last time had got until here,

We don’t need specify data type with python something similar to javascript where we use var for every type of variable.(const and let are new ES6 standards, although they are not new but new)

So basically

1
2
3

a = 10
b = 1.0
c = "test"

in above a become integer, b becomes float and c becomes string.

Reading input from the Keyboard

For taking input from client we can input("string to show while taking input"). PS: while taking input it would always be strings similar to command line input in C. So we would type cast it into required datatype. For example integer or float. As it is already string we don’t need to typecast if we need a string.

Some mathematical operations BODMAS

python operations would follow BODMAS, and we can evaluate any operations as follows: We would create si.py file with below text. Please note #!/usr/bin/env python3 is very important line without which you would get an error in your code while running file.(Saying with experience)

#!/usr/bin/env python3
p = float(input("Enter amount: "))
r = float(input("Enter Interest rate: "))
n = int(input("Enter period: "))
si = (p*r*n)/100
print("Simple Interest: %.2f" % si)

Multiple assignments on variable

Is a way to assign value to multiple in a single go(Title itself makes it clear)

>>> a , b = "test", "test1"
>>> a
'test'
>>> b
'test1'

A question which is always part of any programming language you learn in college, how to swap two number with and without using third variable. In python because of multiple assignment approach things becomes easy.

>>> a , b = "test", "test1"
>>> a
'test'
>>> b
'test1'
>>> a , b = b, a
>>> a
'test1'
>>> b
'test'

Formating our printed strings

There are several ways to format strings one of them we saw before in codes above:

using %

`1`	`print("Simple Interest: %.2f" % si)`

using .format

>>> name = "Python"
>>> typeof = "snake"
>>> msg = "{0} is {1}.".format(name, typeof)
>>> print(msg)
Python is snake.

using f-strings(More to read:link)

>>> name = "Python"
>>> typeof = "snake"
>>> msg = f"{name} is {typeof}."
>>> print(msg)
Python is snake.

I find f-string more easy because it somewhat similar syntax to template string in javascript.

Operators and expressions

In Python most of the lines you will write will be expressions. Expressions are made of operators and operands. An expression is like 2 + 3 .

Operators

Operators are symbols which tell python interpreter to do mathematical or logical operations ie. addition, subtraction and etc.

# addition
>>> 2 + 3
5
# subtraction
>>> 23 - 3
20
# divide
>>> 22.0 / 12
1.8333333333333333
# modulo
>>> 14 % 3
2

Example why python is awesome

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2
3

#!/usr/bin/env python3
days = int(input("Enter days: "))
print("Months = %d Days = %d" % (divmod(days, 30)))

Save above code in days.py file. When you run this file as ./days.py it would ask you to enter days you enter let say 50 then it would print both months and remaining days with single function because the divmod(num1, num2) function returns two values , first is the division of num1 and num2 and in second the modulo of num1 and num2.

Above code could also be written as follows the longer way:

#!/usr/bin/env python3
days = int(input("Enter days: "))
months = days / 30
days = days % 30
print("Months = %d Days = %d" % (months, days))

Relational Operators

Similar many programming language although below is reference table.

Operator	Meaning
<	Is less than
<=	Is less than or equal to
>	Is greater than
>=	Is greater than or equal to
==	Is equal to
!=	Is not equal to

Some examples also:

>>> 1 < 2
True
>>> 3 > 34
False
>>> 23 == 45
False
>>> 34 != 323
True
# '//' Gives floor division result, could be useful at many places where you would call floor function
>>> 4.0 // 3
1.0
>>> 4.0 / 3
1.3333333333333333

Logical Operators

Note for self: There is difference between logical and bitwise operators. Please don’t get confused. In logical operators when first value is not true then it would return second value

>>> 1 and 4
4
>>> 1 or 4
1
>>> -1 or 4
-1
>>> 0 or 4
4

Shorthand Operators

When you perform operation on same variable where you are storing value for example.

>>> a = 12
>>> a += 13
>>> a
25
>>> a /= 3
>>> a
8.333333333333334
>>> a += (26 * 32)
>>> a
840.3333333333334

Expressions

General rule whenever you write any operator give spaces between them. Evaluation of expression follows BODMAS. For example in following code evaluation of x,y,z would be:

#!/usr/bin/env python3
a = 9
b = 12
c = 3
x = a - b / 3 + c * 2 - 1
y = a - b / (3 + c) * (2 - 1)
z = a - (b / (3 + c) * 2) - 1
print("X = ", x)
print("Y = ", y)
print("Z = ", z)

For x:

9 - 12 / 3 + 3 * 2 -1
9 - 4 + 3 * 2 - 1
9 - 4 + 6 - 1
5 + 6 - 1
11 - 1
10

for y:

a - b / (3 + c) * (2 - 1)
9 - 12 / (3 + 3) * (2 - 1)
9 - 12 / 6 * 1
9 - 2 * 1
9 - 2
7

for z:

a - (b / (3 + c) * 2) - 1
9 - (12 / (3 + 3) * 2) - 1
9 - (12 / 6 * 2) - 1
9 - (2 * 2) - 1
9 - 4 - 1
4

Type Conversions

As we were saw previously we were converting string input into float and integers. So is a example of how you do it.

1
2
3

float(string) -> float value
int(string) -> integer value
str(integer) or str(float) -> string representation

Learning python through pym 10-08-2019

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Sat, 10 Aug 2019 17:59:22 +0530

Day 1

Installing python

one can install python using package manager depending upon the operating system you are using. As I have a windows machine and ubuntu using linux on windows subsystem. I can install python from https://python.org. And Ubuntu I can use below command to install python.

`1`	`sudo apt-get install python3`

Running python

To run python you would call python3 which open Python interpreter. On that you can type print(“Hello World”) to run your first python code which would print Hello World in next line.

To run python code from a file I would need to below text into a file, save suppose as hello.py

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2

#!/usr/bin/env python3
print("Hello World!")

The file “hello.py” needs to be executable to be run the code. If file is not executable we can do it by chmod +x hello.py

then we can run file by calling it as ./hello.py

White space and indentation

Whitespace and indentation should be perfect for python. If a line is not correctly indented python interpreter would Indentation error. There are few basic rule to follow,

Use 4 spaces for indentation
Never mix tab and spaces
One line blank after functions
two lines blank after classes.
add a space after “,” in dicts, lists, tuples and argument list and after “:” in dicts
Spaces around assignments and comparers
no spaces after starting and before ending () brackets/parentheses

Comments

In python on can write comments starting with ‘#’ Still gonna check whether to use ’’’ for multiline comments or not. links:

Modules

Modules are link library which you can in import and run function from it.

Keywords and Indentifier

As any other language there are reserved keywords in python which cannot be used as ordinary identifiers. Below is the list of identifiers. Note: Identifiers are case sensitive they should be used with same casing.

and del from not while
as elif global or with
assert else if pass yield
break except import print
class exec in raise
continue finally is return
def for lambda try

We don’t need specify data type with python something similar to javascript where we use var for every type of variable.

Object-Oriented Programming With JavaScript (part 1)

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Mon, 29 Jul 2019 16:56:15 +0530

I started to learn Object-oriented Programming in JavaScript using this course. This post is more of notes for the course I am taking.

Object-oriented programming is a programming paradigm or style of programming which is centered around objects and not on functions.

Four core concept or pillars of Object-oriented programming language

Encapsulation
Abstraction
Inheritance
Polymorphism

In Object-oriented programming we combine related functions and variables and call them as object.

Before Object-oriented programming we had procedural programming, which divided program into set of functions.

More information about git log command

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Mon, 22 Jul 2019 21:59:52 +0530

As part of home task part 2, we were asked to read about git log command. So this blog post is dedicated to that. To get more info about git log command I had gone through Git pro book available at https://git-scm.com/book/en/v2/. From this book I had followed chapter https://git-scm.com/book/en/v2/Git-Basics-Viewing-the-Commit-History to study more about git log command.

When git log is used without any argument, it displays all previous commits in reverse chronological order.

`1`	`$ git log`

We can provide following arguments with git log command to see different outputs formats.

When -n is passed as an argument, where n is number it would show n number of commits.

`1`	`$ git log -5`

When -p or --patch is passed as an argument, it shows difference or patch output between each commit

`1`	`$ git log -p -5`

--stat is used get abbreviated stats of each commits

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2

$ git log --stat
$ git log --stat -2

--since=<date> is used get logs from a particular time. One can pass months, years, days, hours etc to get log from that particular time.

$ git log --since="2 hours"
$ git log --since="3 day"
$ git log --since="10 weeks"
$ git log --since="1 year"

--author=<pattern> is used get logs from one or many authors.

`1`	`$ git log --author="Bhavesh"`

Bonus Video: Thanks for reading the post check out this video on youtube explaining how git works internally.

Introduction to Git and seven rules of great Git Commit Message

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Mon, 22 Jul 2019 12:12:00 +0530

As part of summer training at #dgplug, Sayan took our basics to Git session. We were introduced to basics of VCS(Version Control System), need to use a VCS and introduction to Git.

These were some of commands we learn during the session conducted over the course of two days,

git init is used initialize Git repository
```
$ git init
```
git config to used to configure various Git configuration using below command one can configure their Name and Email globally for Git.
```
$ git config --global user.name "<Name>"
$ git config --global user.email "<email>"
```
git add is used to add files to stage area in Git.
```
$ git add helloworld.txt
$ git add .
$ git add -u
```
git status to see status of you Git repository. Whether there are changes that are still not added to stage or there are changes which are added to stage but not committed.
```
$ git status
```
git commit is used to commit your files from stage.
```
$ git commit -m "Snapshot 2"
```
git diff is used to difference between current state and previous state.
```
$ git diff
```

git log is used to get commit logs.

$ git log
$ git log -2
$ git log -p -2
$ git log --stat

As part of home task we were asked to read https://chris.beams.io/posts/git-commit/, which explains How to write a Git commit message.

The seven rules of a great Git commit message are:

Separate subject from body with a blank line
Limit the subject line to 50 characters
Capitalize the subject line
Do not end the subject line with a period
Use the imperative mood in the subject line
Wrap the body at 72 characters
Use the body to explain what and why vs. how

Birthday Week 2019

BhaveshSGupta@disroot.org (Bhavesh S. Gupta) — Thu, 23 May 2019 19:30:00 +0000

So another Birthday gone as-usual. Although I am not a big celebrator expect last where we had a trip to Rishikesh on my birthday PS: I am yet to write that post.

My celebration to birthday most part has only dinner with family. We go to a fancy hotel have some food and come back. Its almost like this has become a tradition to celebrate birthday this way.

This post was to be published on 19th May, instead I am writing now because of my laziness I don’t often write due to fear of writing or fear of making mistakes while write. Although I plan to write and read more. :)