My Python Code That Converts Numbers Between Bases Has Several Errors. What Could Be Wrong And How Can I Find Them?

My program is a function that converts numbers from one base to another. It takes three arguments: the initial value, the base of the initial value, then the base it is to be conve

Solution 1:

Without going into specific problems with your code, which as you stated are many, I'll give a brief answer to the actual question in the title

What could be wrong and how can I find [the errors in my code]?

Rather than treating your code as one big complicated function that you have to stare at and understand all at once (I can rarely hold more than 10 lines of code in my own internal brain cache at once), try to break it down into smaller pieces "first I do this and expect this result. Then I take that result and do this to it, and expect another result."

From your description of the problem it seems like you're already thinking that way, but you still dumped this big chunk of code and seemed to struggle with figuring out exactly where the problem is. A lot of beginners will write some big pile of code, and then treat it as a black box while testing it. Like "I'm not getting the right answer and I don't know where the problem begins." This is where learning good debugging skills is crucial.

I would first break things into smaller pieces to just try out at the interactive Python prompt. Put in dummy values for different variables and make sure small snippets of code (1 to 5 lines or so, small small enough that it's easy to reason about) do exactly what you expect to do with different values of the variables.

If that doesn't help, then for starters the tried and true method, often for beginners and advanced developers alike, is to riddle your code with print statements. In as many places as you think is necessary, put a statement to print the values of one or more variables. Like print("exp = %s; result = %s" % (exp, result). Put something this in as many places as you need to trace the values of some variables through the execution. See where it starts to give answers that don't make sense.

Sometimes this is hard to do though. You might not be able to guess the most effective places to put print statements, or even what's important to print. In cases like this (and IMO in most cases) it is more effective to use an interactive debugger like Python's built in pdb. There are many good resources to learn pdb but the basics shouldn't take too long to get down and will save you a whole lot of headache.

pdb will run your code line-by-line, stopping after each line (and in loops it will step through each loop through the loop), allowing you to examine the contents of each variable before advancing to the next line. This gives you full power to check that each part of your code does or doesn't do what you expect, and should help you pinpoint numerous problem areas.

Solution 2:

You should use the exp you find in the first step:

while int(decimalResult)>=(cbase2**exp):
    exp=exp+1
exp -= 1
while exp >= 0:
    ...
    finalResult=str(finalResult)+str(result)
    decimalResult=decimalResult%cbase2**exp
    exp -= 1

Solution 3:

First of all, the entire first part of the code is not needed, as the int function does it for you. Instead of all that, you can do this.

int(cnum, base=cbase1)

This converts cnum from cbase1 to base 10.

The second part might go to an infinite loop because at the bottom, it says

exp = exp + 1

When it should say

exp = exp - 1

Since you want to go from (for example) 5^2 to 5^0.

The resulting not having the last digit is because it breaks out of the loop at exp = 0. It doesn't actually add the digit to the result. A simple fix for that is

finalResult = str(finalResult) + str(decimalResult)