using xrange output not expected

Question

s = 0

for s in xrange(0, 100):
    print "s before", s
    if s % 10 == 0:
        s += 10
    print "s after", s

result of loop1

s = 0

while s < 100:
    print "s before", s
    if s % 10 == 0:
        s += 10
    s += 1
    print "s after", s

result of loop2

As pictures shown above, why those 2 loops doing similar things, one using xrange while another using while-loop are giving me exact different output?

Because `for` sets `s` from the iterable, and setting `s` to something else in the loop doesn't change the iterable. — Martijn Pieters, Aug 09 '17 at 08:35
You are essentially asking why `s = first_thing` then `s = second_thing` didn't change `first_thing`. — Martijn Pieters, Aug 09 '17 at 08:36

Mohamed Ali JAMAOUI · Accepted Answer · 2022-04-17T08:29:33.187

2

s in the first loop is overwritten by the values coming from xrange(0, 100) whereas in the second loop you are manually initializing the variable s=0 and then incrementing it with s += 10. So, it's exactly the expected behavior.

You need to have a look into variable scopes in python. Check this discussion: Short description of the scoping rules?

edited Apr 17 '22 at 08:29

answered Aug 09 '17 at 08:36

Mohamed Ali JAMAOUI

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Thank you very much for ur answer and ur link shared. – Sam Y Aug 10 '17 at 05:52
Thanks very much and sorry for the late reply. And most importantly, you solved my problem. – Sam Y Jan 30 '19 at 13:46

using xrange output not expected

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