and is not a logical conjugation

[theiain]

BPO	11737
Nosy	@ezio-melotti

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2011-04-01.14:35:00.302>
created_at = <Date 2011-04-01.14:22:55.520>
labels = ['invalid']
title = 'and is not a logical conjugation'
updated_at = <Date 2011-04-01.14:35:00.279>
user = 'https://bugs.python.org/theiain'

bugs.python.org fields:

activity = <Date 2011-04-01.14:35:00.279>
actor = 'ezio.melotti'
assignee = 'none'
closed = True
closed_date = <Date 2011-04-01.14:35:00.302>
closer = 'ezio.melotti'
components = []
creation = <Date 2011-04-01.14:22:55.520>
creator = 'the_iain'
dependencies = []
files = []
hgrepos = []
issue_num = 11737
keywords = []
message_count = 2.0
messages = ['132740', '132741']
nosy_count = 2.0
nosy_names = ['ezio.melotti', 'the_iain']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue11737'
versions = ['Python 2.7']

[theiain]

The documentation here: http://docs.python.org/library/stdtypes.html
indicates that and operates as such
{if x:
return x
else:
return y}

to be a logical conjugation it should function as
{if x:
if y:
return True
return False}

The it is now (False and True) will return True. Basic logic asserts that this is not the case.

[ezio-melotti]

The doc0 says:
"""
x and y: if x is false, then x, else y
"""
Boolean operators in Python always return one of the two values (rather than True/False), and they are also short-circuit operators, so:

• if x is false, the whole expression is false regardless of the value of y, so x is returned without evaluating y;
• if x is true, y could be either:
  • true: so the whole expression is true and y is returned;
  • false: so the whole expression is false and y is returned;

>>> '' and True
''
>>> True and ''
''
>>> True and 15
15

The behavior matches the documentation and (False and True) returns False, because x (False in this case) is false.