Python for-else relationship

Question

I can run the below python script without errors.

for n in range(3):
    print n
else:
    print "done"

But I am puzzled about the else without a matching if.
It does not make sense.
Can some one explain why this works ?

Related post: http://stackoverflow.com/questions/9979970/why-does-python-use-else-after-for-and-while-loops — gr3co, Aug 08 '13 at 02:25
Paraphrasing Raymond Hettinger, "if we had just called it `nobreak`, nobody would ever be surprised by it." — roippi, Aug 08 '13 at 02:27

score 7 · Accepted Answer · answered Aug 08 '13 at 02:25

7

The else clause of for and while only executes if the loop exits normally, i.e. break is never run.

for i in range(20):
  print i
  if i == 3:
    break
else:
  print 'HAHA!'

And the else clause of try only executes if no exception happened.

try:
  a = 1 / 2
except ZeroDivisionError:
  do_something()
else:
  print '/golfclap'

answered Aug 08 '13 at 02:25

1

+1 for expanding on the original question by showing how it is used with `try` – Brian Aug 08 '13 at 02:44

score 3 · Answer 2 · answered Aug 08 '13 at 02:25

3

The body of the else is executed after the for loop is done, but only if the for loop didn't terminate early by break statements.

answered Aug 08 '13 at 02:25

jh314

2 Answers2