Any object can be tested for truth value, for use in an
if
or
while
condition or as operand of the Boolean operations below. The
following values are considered false:None
False
- zero of any numeric type, for example,
0
,0L
,0.0
,0j
. - any empty sequence, for example,
''
,()
,[]
. - any empty mapping, for example,
{}
. - instances of user-defined classes, if the class defines a
__nonzero__()
or__len__()
method, when that method returns the integer zero orbool
valueFalse
. [1]
All other values are considered true — so objects of many types are always
true.
Operations and built-in functions that have a Boolean result always return
0
or False
for false and 1
or True
for true, unless otherwise stated.
(Important exception: the Boolean operations or
and and
always return
one of their operands.)
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