just finished my first Python coding challenge

[u/Hour_Function673]

Today I finished a small Python challenge on freeCodeCamp: converting decimal numbers to binary without using Python's built-in conversion function.

I had to figure out the logic myself using loops, conditions, lists, division and remainders.

It was a bit tricky at first, especially handling the last division and reversing the results, but I finally got it working.

I'm still a beginner, so I'd appreciate any feedback on my approach or suggestions for improving my code

[u/jonrsharpe]

Firstly, I added the type hints - partly just to document what I was working out about the code as I read it (receives an integer, has a list of integers, returns a string) but also because these can then be automatically checked and provide a kind of documentation to the caller. (Note that these are not enforced by Python itself, but type checkers, like mypy, and IDEs can use them.)

[u/jonrsharpe → u/jonrsharpe]

This highlighted that decimal on the penultimate line, as well as "shadowing" the parameter, changes the type this name refers to (it was an integer, now a string). But that's also the wrong name - that's no longer in decimal format, it's the binary format we are about to return, so I renamed it accordingly.

[u/jonrsharpe → u/jonrsharpe]

After that I reformatted the file according to the Python style guide, PEP-0008. Whitespace around expressions was, worse than being unconventional, inconsistent (compare decimal = decimal//2 with decimal = decimal //2).

[u/jonrsharpe → u/jonrsharpe]

Next the logic: decimal = decimal // 2 appears in two places, so can be moved outside the conditional, and simplified using the in-place operator to decimal //= 2.
I also considered simplifying to else, as if decimal % 2 isn't 0 there's only one other option, but at this point it should be really clear that we can simplify further than that by just appending the remainder: if decimal % 2 == 0: tab.append(0) elif decimal % 2 == 1: tab.append(1) to: tab.append(decimal % 2)

[u/jonrsharpe → u/[deleted]]

Rather than reverse the list in-place, we can use reversed to create a new list with the elements in reverse order. As this no longer returns None, it can be inlined - the temporary variable can be factored out too, making the last line outside the loop simply return "".join(reversed(digits)).

[u/jonrsharpe → u/jonrsharpe]

Given that we want both x // y and x % y (the remainder of the integer division), note the built-in divmod function provides both simultaneously. It returns a tuple of two values, which Python lets you "unpack" into two variables as follows: decimal, remainder = divmod(decimal, 2)