Having some trouble with indexes in my code.

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Hi all, I am working on some code for a homework problem that requires me to transfer comments into python3 code. I keep getting an error that says index is undefined and so I can't run the code. The output is meant to list how many of each number is in a given string. For example, in the string (1,1,1,3,3,3,3) it would output (1,3,3,4) as there are 3 ones and 4 threes. Here is the code:

def RLE(myList):
newList = []
myList = []
i = 0
while i < len(myList):
currentChar = myList[i]
currentCount = 1
while (i+currentCount < len(myList) and
myList[i+currentCount] == currentChar):
currentCount = currentCount + 1
currentChar.append(newList)
currentCount.append(newList)
i = i + currentCount
return newList

What I have tried:

I have tried different ways of writing index either as i or spelled out as index. The original comment that started my troubles is

Set currentChar equal to the element in myList with index i

. I figured out how to do that sort of and now it says index is undefined despite defining it as zero at the beginning.

Posted 26-Mar-19 12:00pm

Member 14198430

Updated 26-Mar-19 14:22pm

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Patrice T · Answer 1 · 2019-03-26T14:23:00

I commented you source code:

Python

def RLE(myList): # here, myList is the parameter array
   newList = []
   myList = [] # but here, you kill its contains
   i = 0
   while i < len(myList):
      currentChar = myList[i]
      currentCount = 1
      while (i+currentCount < len(myList) and
            myList[i+currentCount] == currentChar):
         currentCount = currentCount + 1
         currentChar.append(newList) # starting here, the indentation look weird
         currentCount.append(newList)
         i = i + currentCount
         return newList

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

27.3. pdb — The Python Debugger — Python 3.6.1 documentation[^]
Debugging in Python | Python Conquers The Universe[^]
pdb – Interactive Debugger - Python Module of the Week[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.