co-test

python-scripting

2 min read

Source: Python Scripting — Connected Objects

Passing Script Arguments

sys.argv

import sys
# python myscript.py first 2 True
# sys.argv = ['myscript.py', 'first', '2', 'True']
  • Always a list of strings
  • First element is always the script name

argparse (preferred)

import argparse
 
parser = argparse.ArgumentParser()
 
# Positional (mandatory, order matters)
parser.add_argument("word", type=str)
parser.add_argument("number", type=int)
parser.add_argument("toggle", type=bool)
 
args = parser.parse_args()
print(args.word, args.number, args.toggle)

Run: python myscript.py first 2 True

# Optional arguments (use -- prefix, order doesn't matter)
parser.add_argument("--word", type=str)
parser.add_argument("--number", type=int)

Run: python myscript.py --word first --number 2 Missing optional args → value is None.

argparse auto-generates --help / error messages.

__name__ and Top-Level Environment

When Python runs a file, __name__ is set to:

  • "__main__" if the file is run directly (python my_script.py)
  • The module name (filename without .py) if the file is imported by another script
# When imported: __name__ == "your_script"
# When run directly: __name__ == "__main__"
print(__name__)

The if __name__ == "__main__": guard

def main():
    # your real logic here
    pass
 
if __name__ == "__main__":
    main()   # only executes when run as a script, not when imported

Why use it: Prevents top-level code from running when your file is imported as a module by another script.

See Also

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