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, Dec 06 '16 at 23:10
You could use argparse(http://stackoverflow.com/questions/15008758/parsing-boolean-values-with-argparse) which is a part of the standard library. Among third party libraries Click can be a good option(http://click.pocoo.org/5/options/#boolean-flags). — Vikas Tikoo, Dec 06 '16 at 23:14

score 18 · Accepted Answer · answered Dec 07 '16 at 00:15

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.

Thmei Esi · Answer 2 · 2016-12-07T00:32:50.357

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 07 '16 at 00:32

answered Dec 06 '16 at 23:12

Thmei Esi

434
2
9

2

`bool` does not convert `"True"` and `"False"` to `True` and `False`. Calling `bool` on a string is equivalent to `len(string) != 0`. – user2357112 Dec 07 '16 at 00:17
Yes, I fixed this. – Thmei Esi Dec 07 '16 at 00:33
Suggest to avoid `eval`, it may have security implications. You may want to use `ast.literal_eval()` instead. – ideasman42 Jul 13 '23 at 02:24

Robert Ribas · Answer 3 · 2022-04-13T15:27:08.750

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

How to write boolean command line arguments with Python?

3 Answers3