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Python equivalent for perl's "next"-statement?

John J. Lee jjl at pobox.com
Wed Oct 22 14:12:13 EDT 2003 
Helmut Jarausch <jarausch at skynet.be> writes:
> Gerhard Häring wrote:
[...]
> Unfortunately, that's not the full truth.
> In Perl the 'next' and 'last' instructions may refer
> to a label of an (outer) loop and thus perform the action
> for that specific outer loop.
> Such possibilities are sadly missing in Python.
> In the case of 'last' one can raise an exception,
> while for 'next' I am not aware of an elegant solution.

Python doesn't have a continue block (suite?) either, which would be
nice to have where you have continues in a loop (especially when there
are several of them) and you want to move your loop variable on to the
next in some sequence:

while condition(foo):
    ...
    if hmm(): continue
    ...
    if hmph(): break
    ...
    if hrm(): continue
    ...
continue:
    # Always called before while conditional evaluated
    # (ie. either on continue or falling off the end of the loop body).
    foo = foo**2


It's already a keyword, so no code breakage.  And it makes more sense
in Python than it does in Perl, since it matches up with the current
meaning of continue (in Perl, a 'next' causes execution of the
'continue' block).

Without this, you have to scatter repeated function calls all over the
place:

def next_foo(foo):
    return foo**2

while condition(foo):
    ...
    if hmm():
        foo = next_foo()
        continue
    ...
    if hmph(): break
    ...
    if hrm():
        foo = next_foo()
        continue
    ....
    foo = next_foo()


Yuck!


John
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