Infinite while loop in python

Question

No matter what I do, I can't get this while loop to work; unless i hardcode the value in.

count = 0
value = raw_input('How many?')
print value
while (count <= value):
        print "a"
        count= count + 1

At first I tried using a command line argument, using sys.argv[1] for value but I got the same problem. This seems so simple, yet I cannot for the life of me figure out what I'm doing wrong.

Try to check - what type is your value? And what type is your count variable? — slallum
– slallum, Commented Sep 4, 2012 at 10:20
After fixing the datatype issues mentioned by others, there's a slightly more concise and pythonic way to write the loop: for i in xrange(value): print "a". — abought
– abought, Commented Sep 5, 2012 at 3:33

Andy Hayden · Accepted Answer · 2012-09-04 10:25:38Z

9

Ensure that value is an integer,

while (count <= int(value)):
    count= count + 1

By default raw_input is a string, and for every integer n and every string s we have n<s is True (!), hence your loop (without the int) never breaks.

Note: In Python 3 comparing string and integers will give a TypeError: unorderable types: str() < int(), which is probably more "expected" behaviour.

edited Sep 4, 2012 at 10:25

answered Sep 4, 2012 at 10:20

Andy Hayden

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2 Comments

jjjjj Over a year ago

Thank you. I didn't even think about that.

lvc Over a year ago

Also note that this now behaves a bit better in Python 3 - '5' < 4 gives an error that tells you exactly what's going on, rather than a meaningless result.

Akhil Thayyil · Accepted Answer · 2012-09-04 10:21:33Z

1

Convert your input to an integer first

value = int(raw_input('How many?'))
print value

answered Sep 4, 2012 at 10:21

Akhil Thayyil

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1 Comment

Colin O'Coal Over a year ago

... but dont' forget to try->catch the possible ValueErrorException, which can be raised if the input is not a number representation!

iscander.drake · Accepted Answer · 2012-09-04 10:51:56Z

1

By the way, if you really want to get your statement to be value times printed change condition from

count <= int(value)

to

count < int(value)

or start count from 1

answered Sep 4, 2012 at 10:51

iscander.drake

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