Visual Studio, per solution indentation settings

Maybe I'm just crazy, but why don't you just press Shift + Tab instead of backspace if you want to get rid of the tabs?

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)