IndentationError: unindent does not match any outer indentation level

IMPORTANT: Spaces are the preferred method - see PEP 8 Indentation and Tabs or Spaces?. (Thanks to @Siha for this.)

For Sublime Text users:

Set Sublime Text to use tabs for indentation: View --> Indentation --> Convert Indentation to Tabs

Uncheck the Indent Using Spaces option as well in the same sub-menu above. This will immediately resolve this issue.

Other posters are probably correct...there might be spaces mixed in with your tabs. 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)