CODEWITHSUNDEEP
pythonpython-2.7while-loop
coolstoner
coolstoner

Reputation: 799

infinite while loop in python when integer compared with range

my while code:

i=0
    a = range(100)
    while i < range(100):
        print i
        i += 9

this goes into an infinite loop...may i know why?

is it because an integer is compared to the list? but what happens when i becomes greater than 99?

shouldnt it come out of the while loop?

below code works fine as expected:

i=0
        a = range(100)
        a_len = len(a)
        while i < a_len:
            print i
            i += 9

Upvotes: 0

Views: 183

Answers (2)

Vaibhav Bajaj
Vaibhav Bajaj

Reputation: 1934

range(100) is a list of integers from 1 to 100 over which you are supposed to iterate. So, len(range(100) = 100. In python 2.x, a list is always greater than an integer. A very simple way to fix this problem is:

i=0
while i < 100: # instead of range(100)
    print i
    i += 9

Upvotes: 0

Jon Clements
Jon Clements

Reputation: 142136

Sadly in Python 2.x, an int is always less than a list (even if that list is empty).

>>> 9 < []
True

What you want to be doing is using the 3-argument form of range so you have a start, a stop and a step, eg:

for i in range(0, 100, 9):
    print i

Upvotes: 8

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