On 14/06/2013 18:28, Michael Torrie wrote:
On 06/14/2013 10:49 AM, Steven D'Aprano wrote:
Correct. In Python, all boolean expressions are duck-typed: they aren't
restricted to True and False, but to any "true-ish" and "false-ish"
value, or as the Javascript people call them, truthy and falsey values.
<snip>
There are a couple of anomalies -- the timestamp representing midnight is
falsey, because it is implemented as a zero number of seconds; also
exhausted iterators and generators ought to be considered falsey, since
they are empty, but because they don't know they are empty until called,
they are actually treated as truthy. But otherwise, the model is very
clean.
Good explanation! Definitely enlightened me. Thank you.
The general rule is that an object is true-ish unless it's false-ish
(there are fewer false-ish objects than true-ish objects, e.g. zero vs
non-zero int).
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