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Python when evaluating loop conditions

Let's say I have the following loop:

i = 0
l = [0, 1, 2, 3]
while i < len(l):
    if something_happens:
         l.append(something)
    i += 1

Will the condition len(i)

in the while loop be updated when something is added to l

?

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2 answers


Yes, it will.



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Your code will work, but using a loop counter is often not considered very "pythonic". Usage for

works just as well and eliminates the counter:

>>> foo = [0, 1, 2]
>>> for bar in foo:
    if bar % 2: # append to foo for every odd number
        foo.append(len(foo))
    print bar

0
1
2
3
4


If you need to know how far the list is, you can use enumerate

:

>>> foo = ["wibble", "wobble", "wubble"]
>>> for i, bar in enumerate(foo):
    if i % 2: # append to foo for every odd number
        foo.append("appended")
    print bar

wibble
wobble
wubble
appended
appended
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