break for loop in Python

Question

is it possible to break a for loop in Python, without break command?
I'm asking this question in order to compare it with C++ for loop, in which actually checks a condition each time.

i.e. it's possible to break a for loop in C++ like below:

for(int i=0; i<100; i++)
    i = 1000; // equal to break;

is it possible to do the same in Python?

for i in range(0,100):
    i = 10000 // not working

Python's `for` is more like C++11's range-based `for`, _not at all_ like the original C++ `for`. It iterates over a set of items. — Seth Carnegie, Jan 27 '12 at 18:51
`i = 1000; // equal to break;` Please be kind to your fellow programmers and don't do this. If you want to break, `break`. — R. Martinho Fernandes, Jan 27 '12 at 19:01

score 7 · Accepted Answer · edited Oct 20 '22 at 04:55

7

Python's for is really a "for each" and is used with iterables, not loop conditions.

Instead, use a while statement, which checks the loop condition on each pass:

i = 0
while i < 1000:
    i = 1000

Or use an if statement paired with a break statement to exit the loop:

for i in range(1000):
    if i == 10:
        break

edited Oct 20 '22 at 04:55

Karl Knechtel

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answered Jan 27 '12 at 18:51

Raymond Hettinger

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score 1 · Answer 2 · answered Jan 27 '12 at 18:52

1

Use a while loop for that purpose:

i = 0
while i < 100:
    i = 1000

answered Jan 27 '12 at 18:52

Sufian Latif

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score 1 · Answer 3 · answered Jan 27 '12 at 18:53

No, for doesn't work like that in Python. for iterates over a list (in this case) or other container or iterable. for i in range(0, 100) doesn't mean "increment i until i is greater than or equal to 100", it means "set i to successive items from a list of these 100 items until the list is exhausted."

If i is 50, then the next item of the list is still 51, regardless of what you may set i to.

break is better anyway.

score 0 · Answer 4 · answered Jan 27 '12 at 18:53

This won't work (as you've noticed). The reason is that, in principle, you are iterating the elements of a list of ascending numbers (whether that is really true depends on if you're using python 2 or 3). You can use the 'break' keyword to break out of a loop at any time, although using it in excess might make it hard to follow your code.

score 0 · Answer 5 · answered Jan 27 '12 at 18:53

0

You might have to settle for the break statement:

http://docs.python.org/tutorial/controlflow.html

for i in range(0,100):
    print i
    if i == 10:
        break

answered Jan 27 '12 at 18:53

Andy Arismendi

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break for loop in Python

5 Answers5