Steven D'Aprano wrote:
Python uses a boolean algebra where there are many ways of
spelling the true and false values. The "not" operator returns
the canonical bool values:
Take note of the distinction between lower-case true/false,
which are adjectives, and True/False, which are objects of
class bool.
Yes, yes... to your previous comments, and to move the discussion
forward a bit...
... the interesting thing about this part of the discussion is the
class bool... because it looks like 'list' is being 'promoted' to type
class bool in the following:
if not list: <=== this is not logical on the surface...
... if the equivalent is:
if not bool(list): <=== this is more explicit, and more readable
although it still doesn't tell a casual reader how the bool(list)
evaluates... is it empty? is it name exception? other? I'm just
saying; no need to respond... just that its easier to understand the
syntax of 'not list' in the knowledge that what is happening under the
hood is that the 'not' operator does require a bool() and that list is
being evaluated bool(list) as one of two logical states.
Having played around a little bit with this today I am again
impressed that bool() can take *any* object as a parm and derive the
correct binary state, whatever that happens to be:
bool({}) False
bool([]) False
bool(0) False
bool('') False
bool(()) False
Therefore,
if not str tests for the empty string...
if not dict tests for the empty dictionary...
&etc.
... is at least consistent ...
kind regards,
m harris
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