I would like to use argparse to parse boolean command-line arguments written as “–foo True” or “–foo False”. For example:
my_program --my_boolean_flag False
However, the following test code does not do what I would like:
import argparse
parser = argparse.ArgumentParser(description="My parser")
parser.add_argument("--my_bool", type=bool)
cmd_line = ["--my_bool", "False"]
parsed_args = parser.parse(cmd_line)
Sadly, parsed_args.my_bool
evaluates to True
. This is the case even when I change cmd_line
to be ["--my_bool", ""]
, which is surprising, since bool("")
evalutates to False
.
How can I get argparse to parse "False"
, "F"
, and their lower-case variants to be False
?
24 s
I think a more canonical way to do this is via:
command --feature
and
command --no-feature
argparse
supports this version nicely:
Python 3.9+:
parser.add_argument('--feature', action=argparse.BooleanOptionalAction)
Python < 3.9:
parser.add_argument('--feature', action='store_true')
parser.add_argument('--no-feature', action='store_false')
parser.set_defaults(feature=True)
Of course, if you really want the --arg <True|False>
version, you could pass ast.literal_eval
as the “type”, or a user defined function …
def t_or_f(arg):
ua = str(arg).upper()
if 'TRUE'.startswith(ua):
return True
elif 'FALSE'.startswith(ua):
return False
else:
pass #error condition maybe?