In python the usual code style is to use snake_case.

Thanks for pointing that out. I’ll update the variable.

Could you please wrap you logic into a method and run it using if __name__ == "__main__": approach? Ideally the program should not contain global vars, and having methods improves readability.

Thanks for the suggestion. I’ve moved the logic into functions, added a main() entry point using if name == "main": and removed global variables to improve readability.

cat -n sample-files/1.txt, cat.py sample-files/ *.txt (including -n option) and cat -b sample-files/3.txt all show slightly different result from yours.

There is a method in python to read file into an array of lines directly.

Thank you for the suggestion. I’ll use the built-in method to read the file into a list of lines directly.

You can potentially use enumerate here.

Again, formatting could be improved with ruff here or other formatters :)

Thank you for the suggestion @DaryaShirokova.
I’ve formatted the code using ruff to improve consistency and readability.

What do you mean by long listing format here?

Many thanks for your time and help.
I’ll update the help text to reflect that.

Can these two functions be merged into one using extra method param?

Thanks for the suggestion.
I merged them into a single function with an extra parameter.

Can you rework this code to have less duplication, by using methods?

Thank you for your feedback, I’ve refactored the code to reduce duplication.

Please enasure your output is the same as the one suggested for examples in the readme (it is ok if whitespaces are different in your output):

It must act the same as `wc` would, if run from the directory containing this README.md file, for the following command lines:

* `wc sample-files/*`
* `wc -l sample-files/3.txt`
* `wc -w sample-files/3.txt`
* `wc -c sample-files/3.txt`
* `wc -l sample-files/*`

This works, but often when doing this kind of "there are a few ways we may want to change things, but we're doing the same thing at its core", we try to structure code to emphasise what's the same/different, so something like:

for line in lines:
    prefix = ""
    if args.n or (args.b and line.strip() != ""):
        prefix = counter_number
        counter_number += 1
    print(f"{prefix} {line}")

This makes clear that regardless of flags, we're doing something for each line, we're printing the line, and we may print something different at the start.

It particularly helps when we end up with lots of different combinations, to think how each affects what we're doing, rather than having to handle them all separately.

Thank you @illicitonion. that’s a really helpful suggestion. I’ve refactored the code to emphasise the shared logic and handle the differences through a prefix, as you described.

Same idea here:

if show_hidden or not file.startswith("."):
    print(file)

This way if we change how we print things, we only need to change it in once place, not two.

Thank you for the suggestion @illicitonion. That was a really valuable point.
I have refactored the code to centralise the printing logic.
Many thanks.

What does the variable name fn mean?

When would fn be empty? From the naming here, it's pretty hard to work out what this means.

You're right, Thank you for your feedback @illicitonion .
Since the path argument defaults to ".", the condition would never be false, so I have removed the unnecessary check.
I’ve also renamed the variable to make it clearer that it represents a directory path.

The real wc shows totals even if you specify flags, e.g. wc -c /file/1 /file/2 will show a total row.

Thank you for your feedback, Daniel. I have refactored my code accordingly. please let me know if any further changes are needed. I really appreciate your suggestion.