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---
title: Coding challenge 1 - wc
author: luke
date: 2023-10-30 12:00:00 +0500
categories: [Software Engineering]
tags: [coding projects]
---

Recently, I discovered my passion for software engineering, and have decided to pursue a career as a software engineer (SWE) when I complete my military service. As an aspiring SWE, I'm always looking for new ways to grow my knowledge and skills. I've discovered that I learn most by building real software, but it's often hard for me to think of well-scoped projects.

Enter [John Crickett's](https://www.linkedin.com/in/johncrickett/) [coding challenges](https://codingchallenges.substack.com/)! He has posted dozens (and counting) of well-scoped projects that can usually be completed in ~8 hours. I hope to complete several of them over the next few months (years), starting with `wc`. In this post, I'll walk through my implementation of the unix/linux command-line tool `wc`.

## About
`wc` stands for word count. `py-wc` is my version of the Linux-style command-line tool named `wc`, implemented in Python (hence the 'py' in `py-wc`). As the name implies, its only use is for counting the number of lines, words, bytes, or characters in the files or directories specified in the input arguments.

I decided to code this up in Python since that's the language I'm most familiar with. This allowed me to focus more on the workflow of `wc` and less on the syntax of the language I was working with.

## Instructions
To use this as a command-line tool, I recommend adding the finished script to PATH / system variables. For Windows, create a folder named `Aliases` in your C drive: `C:/Aliases`, and then add this folder to PATH. Next, create a batch file that will execute when you call the specified alias. For example, on my machine, I have a batch file named `wc.bat` located at `C:/Aliases`, that contains the following script:

```bat
@echo off
echo.
python C:\...\GitHub\py-wc\main.py %*
```

So now, when I type `wc` in the command prompt, this batch file will execute, which in turn, runs the `py-wc` Python script.

## Examples

`py-wc` allows you to execute typical Linux-style `wc` commands.

Here we see the line count for a single file:

```cmd
C:\> wc test.txt -l
7145 test.txt
7145 total
lines
```

Byte count:

```cmd
C:\> wc test.txt -c
342185 test.txt
342185 total
bytes
```

Character count:

```cmd
C:\> wc test.txt -m
339289 test.txt
339289 total
chars
```

And word count:

```cmd
C:\> wc test.txt -w
58164 test.txt
58164 total
words
```

You can also mix and match flags:

```cmd
C:\> wc test.txt -w -l
7145 58164 test.txt
7145 58164 total
lines words
C:\> wc test.txt -w -l -c -m
7145 58164 339289 342185 test.txt
7145 58164 339289 342185 total
lines words chars bytes
```

And the order in which you pass the flags does not matter:

```cmd
C:\> wc -w -l test.txt
7145 58164 test.txt
7145 58164 total
lines words
C:\> wc -w -l -c -m test.txt
7145 58164 339289 342185 test.txt
7145 58164 339289 342185 total
lines words chars bytes
```

If you don't pass any flags, you get lines, words, and bytes by default:

```cmd
C:\> wc test.txt
7145 58164 342185 test.txt
7145 58164 342185 total
lines words bytes
```

You can also pass in more than one file:

```cmd
C:\> wc test.txt test2.txt
7145 58164 342185 test.txt
26 136 814 test2.txt
7171 58300 342999 total
lines words bytes
```

Or, you can pass in a directory:

```cmd
C:\> wc test_text
7145 58164 342185 test_text\test.txt
26 136 814 test_text\test2.txt
7171 58300 342999 total
lines words bytes
```

Or multiple directories:

```cmd
C:\> wc test_text test_text2
44 121 1453 test_text\graph.py
21 47 568 test_text\node.py
7145 58164 342185 test_text\test.txt
26 136 814 test_text\test2.txt
7145 58164 342185 test_text2\test.txt
26 136 814 test_text2\test2.txt
14407 116768 688019 total
lines words bytes
```

Finally, you can specify file extensions to ignore:

```cmd
C:\> wc test_text test_text2 -i .py
7145 58164 342185 test_text\test.txt
26 136 814 test_text\test2.txt
7145 58164 342185 test_text2\test.txt
26 136 814 test_text2\test2.txt
14342 116600 685998 total
lines words bytes
```

And you can even specify directory names to ignore! First we call `wc` on a python project, without ignoring any file extensions or directories:

```cmd
C:\> wc matching-algorithms -l
6 matching-algorithms\.gitignore
22 matching-algorithms\README.md
2 matching-algorithms\.git\COMMIT_EDITMSG
16 matching-algorithms\.git\config
1 matching-algorithms\.git\description
2 matching-algorithms\.git\FETCH_HEAD
2 matching-algorithms\.git\HEAD
7 matching-algorithms\.git\index
2 matching-algorithms\.git\ORIG_HEAD
16 matching-algorithms\.git\hooks\applypatch-msg.sample
25 matching-algorithms\.git\hooks\commit-msg.sample
175 matching-algorithms\.git\hooks\fsmonitor-watchman.sample
9 matching-algorithms\.git\hooks\post-update.sample
15 matching-algorithms\.git\hooks\pre-applypatch.sample
50 matching-algorithms\.git\hooks\pre-commit.sample
14 matching-algorithms\.git\hooks\pre-merge-commit.sample
54 matching-algorithms\.git\hooks\pre-push.sample
170 matching-algorithms\.git\hooks\pre-rebase.sample
25 matching-algorithms\.git\hooks\pre-receive.sample
43 matching-algorithms\.git\hooks\prepare-commit-msg.sample
79 matching-algorithms\.git\hooks\push-to-checkout.sample
129 matching-algorithms\.git\hooks\update.sample
7 matching-algorithms\.git\info\exclude
11 matching-algorithms\.git\logs\HEAD
11 matching-algorithms\.git\logs\refs\heads\main
33 matching-algorithms\.git\logs\refs\remotes\origin\HEAD
11 matching-algorithms\.git\logs\refs\remotes\origin\main
12 matching-algorithms\.git\objects\00\0d21fcd4cb2ca6e59ef2b2002cb1048d541f27
4 matching-algorithms\.git\objects\01\6ca9c5ca0ff63978f9922ad01a1825c485a6bd
1 matching-algorithms\.git\objects\03\337b5c7dbec27bf6f6e6924006a0c119807769
6 matching-algorithms\.git\objects\03\efc0b7f527818bb540c6c5584ba612ecc1f594
2 matching-algorithms\.git\objects\04\caa8e53017b4ab5a660ca8fdb2583eb5362ac2
5 matching-algorithms\.git\objects\05\a357455eee5604cf4df366252cfe9c8f2f135e
1 matching-algorithms\.git\objects\09\2bf3e7900f85f5f61af91578883c0a27fbd979
8 matching-algorithms\.git\objects\09\34ea9b62bd31b4bfd8c4299f0c99ba8eb7d074
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2 matching-algorithms\.git\objects\ed\4eca9f0ef03b54f99c8263800709addc1acbad
1 matching-algorithms\.git\objects\f0\068bae1b50f7b8ce62374819becac2c1ac395c
3 matching-algorithms\.git\objects\f4\5f4249e989b919e37e83252eb477b772e4dee0
2 matching-algorithms\.git\objects\f9\4a132a71a830d406fdd437614f12759bb3e825
5 matching-algorithms\.git\objects\fa\19b2bb66dde866581c81e85c2cf1f590252c26
1 matching-algorithms\.git\objects\fb\75d698e6ebc711e2e7e16123ec47c3198b7dd4
2 matching-algorithms\.git\objects\fd\6690d1380958c5f22a25bed4f5ca34bd20f68f
3 matching-algorithms\.git\objects\ff\75481a8bd2251e860820af9fe718d8ed198958
2 matching-algorithms\.git\refs\heads\main
2 matching-algorithms\.git\refs\remotes\origin\HEAD
2 matching-algorithms\.git\refs\remotes\origin\main
21 matching-algorithms\python\data_generator.py
44 matching-algorithms\python\graph.py
21 matching-algorithms\python\node.py
95 matching-algorithms\python\test_da.py
394 matching-algorithms\python\test_ttc.py
39 matching-algorithms\python\algos\da_utils.py
92 matching-algorithms\python\algos\deferred_acceptance.py
61 matching-algorithms\python\algos\top_trading_cycle.py
80 matching-algorithms\python\algos\ttc_utils.py
1 matching-algorithms\python\algos\__init__.py
15 matching-algorithms\python\algos\__pycache__\da_utils.cpython-311.pyc
30 matching-algorithms\python\algos\__pycache__\deferred_acceptance.cpython-311.pyc
34 matching-algorithms\python\algos\__pycache__\top_trading_cycle.cpython-311.pyc
13 matching-algorithms\python\algos\__pycache__\ttc_utils.cpython-311.pyc
2 matching-algorithms\python\algos\__pycache__\__init__.cpython-311.pyc
6 matching-algorithms\python\__pycache__\data_generator.cpython-311.pyc
31 matching-algorithms\python\__pycache__\graph.cpython-311.pyc
6 matching-algorithms\python\__pycache__\node.cpython-311.pyc
2316 total
lines
```

Yikes. Now, let's call `wc` on the same directory, but ignore any compiled python bytecode files (.pyc), .gitignore files, and any .git directories:

```cmd
C:\> wc matching-algorithms -l -i .pyc .gitignore .git
22 matching-algorithms\README.md
21 matching-algorithms\python\data_generator.py
44 matching-algorithms\python\graph.py
21 matching-algorithms\python\node.py
95 matching-algorithms\python\test_da.py
394 matching-algorithms\python\test_ttc.py
39 matching-algorithms\python\algos\da_utils.py
92 matching-algorithms\python\algos\deferred_acceptance.py
61 matching-algorithms\python\algos\top_trading_cycle.py
80 matching-algorithms\python\algos\ttc_utils.py
1 matching-algorithms\python\algos\__init__.py
870 total
lines
```

Much better!

## Libraries
Nothing fancy required - just some basic I/O with Python's built-in `open` function, command-line parsing with the `argparse` library (which comes standard as part of the Python Standard Library), and some directory navigating with `os` (also part of the Python Standard Library).

If you've never used [`argparse`](https://docs.python.org/3/library/argparse.html), I highly recommend it for handling parsing of command-line inputs for programs, here's an example from my repo for this project:

```python
if __name__ == '__main__':
# Create an ArgumentParser object
parser = argparse.ArgumentParser(description='Process text file(s).')

# Add arguments for input file(s) and/or dir(s)
parser.add_argument(
'input_files_or_dirs',
nargs='+',
type=str,
help='Path to the input file(s) and/or dir(s). Pass no options with input file to compute -l (line count), -w (word count), and -c (byte count)'
)

# Add flags for different options, store as True/False
parser.add_argument('-c', '--bytes', action='store_true', help='Count bytes')
parser.add_argument('-l', '--lines', action='store_true', help='Count lines')
parser.add_argument('-w', '--words', action='store_true', help='Count words')
parser.add_argument('-m', '--characters', action='store_true', help='Count characters')

# Add a flag to specify extensions to ignore, set default to empty list, allow multiple args to be passed
parser.add_argument('-i', '--ignore-extensions', default=[], nargs='+', help='List of file extensions to ignore')

# Parse the command-line arguments
args = parser.parse_args()

# Count how many optional flags were passed out of -c, -l, -w, and -m (ignore -i)
optional_flags = sum([args.bytes, args.lines, args.words, args.characters])

# more code below...
```

The full code for this project can be found at my Github [here](https://github.com/lwcarani/py-wc).

## Acknowledgements
Thanks to [John Crickett](https://github.com/JohnCrickett) for the idea from his site, [Coding Challenges](https://codingchallenges.fyi/challenges/challenge-wc)!

Text samples were downloaded from [this](https://www.gutenberg.org/cache/epub/132/pg132.txt) site.

If you happen to peruse my code and notice any bugs or opportunities for optimizations, please let me know!

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