How to write boolean command line arguments with Python?

Question

I would like to write an argument in an application where the argument that I am calling needs to be referenced on the first iteration/run of the script where the initial_run is set to True. Otherwise this value should be left as false. Now this parameter is configured in a configuration file.

The current code that I written is below. What should be changed in this code to return the True value? Now it only returns the value False.

import sys  
# main
param_1= sys.argv[0:] in (True, False)
print 'initial_run=', param_1

Command line arguments are always strings -- the entry point for a C program is specified as int main(int argc, char* argv), and the execv family of syscalls takes arguments as an array of C strings. Since that's how the operating system hands them off, they can't possibly be anything else without being converted, parsed or casted. — Charles Duffy
– Charles Duffy, Commented Dec 6, 2016 at 23:10
You could use argparse(stackoverflow.com/questions/15008758/…) which is a part of the standard library. Among third party libraries Click can be a good option(click.pocoo.org/5/options/#boolean-flags). — Vikas Tikoo
– Vikas Tikoo, Commented Dec 6, 2016 at 23:14

Dalvenjia · Accepted Answer · 2016-12-07 00:15:18Z

20

Running the script from the command line:

# ./my_script.py true

The boolean can be obtined by doing:

import sys

initial_run = sys.argv[1].lower() == 'true'

This way we are doing a comparison of the first argument lowercased to be 'true', and the comparison will return boolean True if the strings match or boolean False if not.

answered Dec 7, 2016 at 0:15

Dalvenjia

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Thmei Esi · Accepted Answer · 2016-12-07 00:32:50Z

3

change

param_1 = sys.argv[0:] in (True, False)

to:

param_1 = eval(sys.argv[1])
assert isinstance(param_1, bool), raise TypeError('param should be a bool')

edited Dec 7, 2016 at 0:32

answered Dec 6, 2016 at 23:12

Thmei Esi

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3 Comments

user2357112 Over a year ago

bool does not convert "True" and "False" to True and False. Calling bool on a string is equivalent to len(string) != 0.

Thmei Esi Over a year ago

Yes, I fixed this.

ideasman42 Over a year ago

Suggest to avoid eval, it may have security implications. You may want to use ast.literal_eval() instead.

Robert Ribas · Accepted Answer · 2022-04-13 15:27:08Z

0

Not sure if may help, what about using argparse?

import argparse

def read_cmdline():
    p=argparse.ArgumentParser()
    p.add_argument("-c","--clear",type=bool, choices=[True,False],required=True)
    args=p.parse_args()
    return args 


if __name__=="__main__":
    args=read_cmdline()
    if args.clear:
        ###actions when clear is True
    else:
        ## actions when clear is False

Note the type=bool in add_argument

edited Apr 13, 2022 at 15:27

answered Apr 13, 2022 at 11:52

Robert Ribas

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