How to use while loops in function in python?

The function raw_input() returns a string, and then you are passing that string onto the function func().

In func() , in the condition for the while loop, you are checking an int against a string.

In Python 2.x , any int is always smaller than any string , hence the loop goes on forever. Example -

>>> 12323123123123121 < '1'
True

You should convert the input to an integer before giving it to the function (or directly when taking the input) . Example -

y = int(raw_input("Give me a number"))

Also, since you are expecting a return value from your function, you should return a value. Currently, you are not returning anything from the function. Example -

while i<k:
    ...
    i=i+1
    print "The numbers are: " , numbers
return numbers

In Python 3.x , this type of comparison is not allowed, if you try to compare string and int with that operator, you would get an error like - TypeError: unorderable types: int() < str() .

There are a couple of big problems with your code:

1. your input is a string, not a number
2. there's no return statement

To solve 1, you must first realize that raw_input gets... raw input; specifically in the form of a str. You must convert it to an int, float, whatever you want. I'll presume you want an integer input for sake of simplicity.

y = int(raw_input("Give me a number"))

Without a return, you can't return a value. In this case, you can't return the m that you want. I'll assume that you want to return numbers once your loop condition fails.

def func(k): 
  print k
  i=0
  numbers = []
  while i<k:
    print "At the top i is %d" %i
    numbers.append(i*i*i)
    i=i+1
    print "The numbers are: " , numbers
  return numbers

I wrote a little script to test -- here it is:

def func(k):
  print k
  i=0
  numbers = []
  while i<k:
    print "At the top i is %d" %i
    numbers.append(i*i*i)
    i=i+1
    print "The numbers are: " , numbers
  return numbers

hello = func(3)
print hello

The output I get is:

3
At the top i is 0
The numbers are:  [0]
At the top i is 1
The numbers are:  [0, 1]
At the top i is 2
The numbers are:  [0, 1, 8]
[0, 1, 8]