PEP308: Yet another syntax proposal

Raymond Hettinger vze4rx4y at verizon.net
Mon Feb 10 18:35:01 CET 2003


"Aahz" <aahz at pythoncraft.com>
> I still have yet to see a clear explanation of why short-circuit is
> necessary and therefore iif() unreasonable.

It is necessary when:
1. One of the alternatives has a side-effect; or
2. one or both alternatives are time consuming; or
3. the validity of the alternatives depends on the outcome
    of the test.

#  Example where all three reasons apply
data = isinstance(source, str)  ??   source.readlines()  ||  source.split()

1. readlines() moves the file pointer
2. for long sources, both alternatives take time
3. split() is only valid for strings and readlines() is only
    valid for file objects.


Raymond Hettinger








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