argparse store false if unspecified
Question:
parser.add_argument('-auto', action='store_true')
How can I store false if -auto is unspecified? I can faintly remember that this way, it stores None if unspecified
Answers:
With
import argparse
parser=argparse.ArgumentParser()
parser.add_argument('-auto', action='store_true', )
args=parser.parse_args()
print(args)
running
% test.py
yields
Namespace(auto=False)
So it appears to be storing False by default.
The store_true option automatically creates a default value of False.
Likewise, store_false will default to True when the command-line argument is not present.
The source for this behavior is succinct and clear: http://hg.python.org/cpython/file/2.7/Lib/argparse.py#l861
The argparse docs aren’t clear on the subject, so I’ll update them now: http://hg.python.org/cpython/rev/49677cc6d83a
store_false will actually default to 0 by default (you can test to verify). To change what it defaults to, just add default=True to your declaration.
So in this case:
parser.add_argument('-auto', action='store_true', default=True)
Raymond Hettinger answers OP’s question already.
However, my group has experienced readability issues using “store_false”. Especially when new members join our group. This is because it is most intuitive way to think is that when a user specifies an argument, the value corresponding to that argument will be True or 1.
For example, if the code is –
parser.add_argument('--stop_logging', action='store_false')
The code reader may likely expect the logging statement to be off when the value in stop_logging is true. But code such as the following will lead to the opposite of the desired behavior –
if not stop_logging:
#log
On the other hand, if the interface is defined as the following, then the “if-statement” works and is more intuitive to read –
parser.add_argument('--stop_logging', action='store_true')
if not stop_logging:
#log
I’ve found the default, when unspecified, to vary between OSX and Linux.
With the following line of code,
parser.add_argument('-auto', action='store_true')
and then omitting -auto from the command line
a Mac results in auto being assigned a value of False, as expected,
whereas on Ubuntu Linux auto is assigned True by default.
parser.add_argument('-auto', action='store_true')
How can I store false if -auto is unspecified? I can faintly remember that this way, it stores None if unspecified
With
import argparse
parser=argparse.ArgumentParser()
parser.add_argument('-auto', action='store_true', )
args=parser.parse_args()
print(args)
running
% test.py
yields
Namespace(auto=False)
So it appears to be storing False by default.
The store_true option automatically creates a default value of False.
Likewise, store_false will default to True when the command-line argument is not present.
The source for this behavior is succinct and clear: http://hg.python.org/cpython/file/2.7/Lib/argparse.py#l861
The argparse docs aren’t clear on the subject, so I’ll update them now: http://hg.python.org/cpython/rev/49677cc6d83a
store_false will actually default to 0 by default (you can test to verify). To change what it defaults to, just add default=True to your declaration.
So in this case:
parser.add_argument('-auto', action='store_true', default=True)
Raymond Hettinger answers OP’s question already.
However, my group has experienced readability issues using “store_false”. Especially when new members join our group. This is because it is most intuitive way to think is that when a user specifies an argument, the value corresponding to that argument will be True or 1.
For example, if the code is –
parser.add_argument('--stop_logging', action='store_false')
The code reader may likely expect the logging statement to be off when the value in stop_logging is true. But code such as the following will lead to the opposite of the desired behavior –
if not stop_logging:
#log
On the other hand, if the interface is defined as the following, then the “if-statement” works and is more intuitive to read –
parser.add_argument('--stop_logging', action='store_true')
if not stop_logging:
#log
I’ve found the default, when unspecified, to vary between OSX and Linux.
With the following line of code,
parser.add_argument('-auto', action='store_true')
and then omitting -auto from the command line
a Mac results in auto being assigned a value of False, as expected,
whereas on Ubuntu Linux auto is assigned True by default.