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bpo-37564: ArgumentParser support bool type according to truth values #14709

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bpo-37564: ArgumentParser support bool type according to truth values #14709

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b2c86bf
Make type bool support some string representations of truth
zachben Jul 10, 2019
7e7cfda
Replace the import of strtobool from distutils.util with local implem…
zachben Jul 14, 2019
c3d3751
Adding news entry in Misc/NEWS.d/next/ for argparse library regarding…
zachben Jul 15, 2019
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19 changes: 19 additions & 0 deletions Lib/argparse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1602,6 +1602,22 @@ def _remove_action(self, action):
self._container._remove_action(action)
self._group_actions.remove(action)

def _strtobool (val):
"""Convert a string representation of truth to true or false.

True values are 'y', 'yes', 't', 'true', 'on', and '1'; false values
are 'n', 'no', 'f', 'false', 'off', and '0'. Raises ValueError if
'val' is anything else.

<Based on strtobool located in module distutils.util>
"""
val = val.lower()
if val in ('y', 'yes', 't', 'true', 'on', '1'):
return True
elif val in ('n', 'no', 'f', 'false', 'off', '0'):
return False
else:
raise ValueError("invalid truth value %r" % (val,))

class ArgumentParser(_AttributeHolder, _ActionsContainer):
"""Object for parsing command line strings into Python objects.
Expand Down Expand Up @@ -1664,6 +1680,9 @@ def identity(string):
return string
self.register('type', None, identity)

# register bool with a type_func that translates string into bool instance logically and gracefully
self.register('type', bool, _strtobool)

# add help argument if necessary
# (using explicit default to override global argument_default)
default_prefix = '-' if '-' in prefix_chars else prefix_chars[0]
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23 changes: 23 additions & 0 deletions Lib/test/test_argparse.py
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Expand Up @@ -1650,6 +1650,29 @@ class TestTypeCallable(ParserTestCase):
('1024.675', NS(eggs=None, spam=1024.675)),
]

class TestTypeBool(ParserTestCase):
"""Test some args with bool type:"""

argument_signatures = [
Sig('mybool', type=bool),
]
failures = ['wrong','123','-1','abc','!@#']
successes = [
('True', NS(mybool=True)),
('False', NS(mybool=False)),
('tRuE', NS(mybool=True)),
('fAlSe', NS(mybool=False)),
('yes', NS(mybool=True)),
('no', NS(mybool=False)),
('y', NS(mybool=True)),
('n', NS(mybool=False)),
('t', NS(mybool=True)),
('f', NS(mybool=False)),
('on', NS(mybool=True)),
('off', NS(mybool=False)),
('1', NS(mybool=True)),
('0', NS(mybool=False)),
]

class TestTypeUserDefined(ParserTestCase):
"""Test a user-defined option/argument type"""
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2019-07-15-22-00-00.bpo-37564.L4ftF7.rst
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@@ -0,0 +1,3 @@
Fix ArgumentParser to treat ``type=bool`` according to common truth values.
Values 'y', 'yes', 't', 'true', 'on', and '1' will be evaluated as True value,
while 'n', 'no', 'f', 'false', 'off', and '0 will be evaluated as False value.