当循环在Python中运行到最后时，如何创建一个for循环，其中变量的值等于范围的停止值？

Question

I'm having a conceptual problem porting this from C to Python:

int p;
for (p = 32; p < 64; p += 2) {
    if (some condition)
        break;
    do some stuff
}
return p;

Converting the loop to for p in range(32,64,2) does not work. This is because after the loop ends, p is equal 62 instead of 64.

I can do it with a while loop easily:

p = 32
while p < 64:
    if (some condition):
        break
    do some stuff
    p += 2
return p

But I'm looking for a Pythonic way .

Answer 1

you can use else for for loop in case condition isn't met to add 2 like C loop does:

for p in range(32, 64, 2):
   if some_condition:
       break
else:
    # only executed if for loop iterates to the end
    p += 2

Answer 2

Extend the range, but include a second "redundant" break condition.

for p in range(32, 65, 2):
    if p >= 64 or (some condition):
        break
    # do stuff

(The only significant difference between this and Jean-François Fabre's answer is which piece of the logic you duplicate: testing if p is out of range, or incrementing p .)

Answer 3

A variation of chepner's answer that avoids duplicating the test would be to use itertools.count :

import itertools

for p in itertools.count(32, 2):
    if p >= 64 or (some condition):
        break
    do some stuff
return p

although I think that might as well be:

p = 32
while True:
    if p >= 64 or (some condition):
        break
    do some stuff
    p += 2
return p

and as tobias_k pointed out, then is trivially transformed to:

p = 32
while p < 64 and not (some condition):
    do some stuff
    p += 2
return p

which I personally think is clearer.