IndentationError: unindent does not match any outer indentation level, although the indentation looks correct

When I compile the Python code below, I get

IndentationError: unindent does not match any outer indentation level

import sys

def Factorial(n): # Return factorial
    result = 1
    for i in range (1,n):
        result = result * i
    print "factorial is ",result
    return result

Why?

One possible cause for this error is that there might be spaces mixed with tabs for indentation. Try doing a search & replace to replace all tabs with a few spaces.

Try this:

import sys

def Factorial(n): # return factorial
    result = 1
    for i in range (1,n):
        result = result * i
    print "factorial is ",result
    return result

print Factorial(10)

Stack Overflow Q#492387, score: 871