Python Command Line Arguments with argparse

Command Arguments

Command line arguments let a script receive values when it starts.

Use argparse when a script needs named options, help text, defaults, or required values.

Arguments make automation scripts easier to reuse because users do not need to edit the source code for every run.

Argument Parser

argparse builds a small command-line interface and converts text arguments into named values.

Create one ArgumentParser.
Add each argument with a clear name.
Read parsed values from args.

Name Argument

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("--name", required=True)
args = parser.parse_args()

print(f"Hello, {args.name}")

Run the file with --name Maya to pass a value from the terminal.

Defaults and Types

Arguments arrive as text, so use type= when the program needs an integer, float, or other conversion.

Use default for optional values.
Use type=int for numbers.
Use action="store_true" for simple on/off flags.

Limit Option

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("--limit", type=int, default=10)
args = parser.parse_args()

print(f"Reading {args.limit} rows")

If --limit is missing, the script uses 10.

Before you move on

Can You Use Command Arguments?

5 checks

You can choose argparse instead of manual sys.argv parsing.
You can create required and optional arguments.
You can set defaults and convert number arguments.
You can add helpful names so --help is useful.
You can keep script configuration outside the source code.

Argument Parsing Traps

Reading sys.argv positions blindly
Use argparse for named values and automatic help text.
Forgetting type conversion
Add type=int or another converter when the value is not meant to stay as text.
Using unclear flag names
Choose names that describe the value: --input, --output, --limit, or --dry-run.

Try this next

Parse a Command

0 of 3 completed

Build a greeting script
Accept --name and --uppercase, then print the greeting in normal or uppercase form.
Add a file argument
Accept --input and check whether the path exists before reading.
Write help text
Add help= text to two arguments and run the script with --help.

Questions About Command Arguments

sys.argv is useful to understand, but argparse is better for real scripts because it gives names, validation, defaults, and help text.

It reads the file path as an argument. Your code still opens and validates the file.

A flag is usually an option such as --verbose or --dry-run that changes behavior without needing a separate value.

Previous Next

Python Command Line Arguments with argparse

Command Arguments

Argument Parser

Name Argument

Defaults and Types

Limit Option

Can You Use Command Arguments?

Argument Parsing Traps

Reading sys.argv positions blindly

Forgetting type conversion

Using unclear flag names

Parse a Command

Build a greeting script

Add a file argument

Write help text

Command Arguments Learning Path

Questions About Command Arguments

Should beginners learn sys.argv first?

Can argparse read files?

What is a flag?

Python Resources

Popular Tutorials