Command-Line Arguments - Windows Python Launcher

The Windows Python Launcher can pass command-line arguments from the batch script to your Python scripts, enabling flexible script execution with runtime parameters.

The passarguments Configuration

The passarguments setting controls whether arguments passed to the launcher are forwarded to your Python script.

# Enable argument passing
set passarguments=1

# Disable argument passing (enables drag and drop)
set passarguments=0

How It Works

When passarguments=1:

Run launcher with arguments

Execute PythonLauncher.bat --arg1 --arg2 value

Launcher finds initial file

Searches for and finds the first matching initial file (e.g., run.py)

Arguments passed to Python

All arguments are forwarded: py -3.11 run.py --arg1 --arg2 value

Python script receives arguments

Access arguments via sys.argv or argument parsing libraries

Configuration Trade-off

Enabling passarguments=1 disables drag and drop functionality. You must choose one or the other.

Setting	Drag and Drop	Command-Line Arguments
`passarguments=0`	Enabled	Disabled
`passarguments=1`	Disabled	Enabled

Why this limitation exists: The launcher uses the first argument (%1) to detect if a file was dragged onto it. When passarguments=1, all arguments are passed to the Python script instead, so the launcher can’t distinguish between a dragged file and a command-line argument.

Code Implementation

From PythonLauncher.bat:135-146:

if !passarguments!==1 (
    rem Run a file with arguments.
    set foundFile=
    for %%f in (%initialfiles%) do (
        if exist %%~f (
            set foundFile=%%~f
            set "command=start %min% "%windowname%" cmd /k ^"call !venvcmd! ^& %pythondir% %pycmd% !foundFile! %* %minexit%^""  
            goto :runFile
        )
    )
    rem If no initial file found, open Python shell
    set command=start %min% "%windowname%" cmd /k "!venvcmd! & %pythondir% %pycmd%"
    goto :runFile
)

Note the %* in the command - this passes all arguments to the Python script.

Usage Examples

Example 1: Basic Argument Passing

Configuration:

set passarguments=1
set initialfiles="run.py" "main.py" "app.py"

Python script (run.py):

import sys

print(f"Script name: {sys.argv[0]}")
print(f"Arguments: {sys.argv[1:]}")

for i, arg in enumerate(sys.argv[1:], 1):
    print(f"  Argument {i}: {arg}")

Running the launcher:

PythonLauncher.bat --verbose --output results.txt

Output:

Script name: run.py
Arguments: ['--verbose', '--output', 'results.txt']
  Argument 1: --verbose
  Argument 2: --output
  Argument 3: results.txt

Example 2: Configuration File Arguments

Python script (main.py):

import sys
import json

def main():
    config_file = "config.json"
    
    # Check for config argument
    if "--config" in sys.argv:
        idx = sys.argv.index("--config")
        config_file = sys.argv[idx + 1]
    
    with open(config_file) as f:
        config = json.load(f)
    
    print(f"Loaded configuration from {config_file}")
    print(f"Settings: {config}")

if __name__ == "__main__":
    main()

Running with custom config:

PythonLauncher.bat --config production.json

Example 3: Using argparse

Python script (app.py):

import argparse

def main():
    parser = argparse.ArgumentParser(description="Process data files")
    parser.add_argument("--input", required=True, help="Input file path")
    parser.add_argument("--output", required=True, help="Output file path")
    parser.add_argument("--format", default="json", choices=["json", "csv", "xml"])
    parser.add_argument("--verbose", action="store_true", help="Enable verbose output")
    
    args = parser.parse_args()
    
    if args.verbose:
        print(f"Processing {args.input}...")
    
    # Process the file
    print(f"Converting {args.input} to {args.format} format")
    print(f"Output will be saved to {args.output}")

if __name__ == "__main__":
    main()

Running with arguments:

PythonLauncher.bat --input data.txt --output result.json --format json --verbose

Output:

Processing data.txt...
Converting data.txt to json format
Output will be saved to result.json

Example 4: Boolean Flags

Python script (run.py):

import sys

# Check for flags
debug_mode = "--debug" in sys.argv
verbose = "--verbose" in sys.argv or "-v" in sys.argv
quiet = "--quiet" in sys.argv or "-q" in sys.argv

if debug_mode:
    print("[DEBUG] Debug mode enabled")

if not quiet:
    print("Starting application...")

if verbose:
    print("Verbose output enabled")
    print(f"All arguments: {sys.argv}")

# Your application logic here
print("Application running")

Running with flags:

PythonLauncher.bat --debug --verbose

Advanced Usage

Passing Arguments with Spaces

When arguments contain spaces, use quotes:

PythonLauncher.bat --message "Hello World" --path "C:\My Documents\file.txt"

Python receives:

sys.argv = ['run.py', '--message', 'Hello World', '--path', 'C:\\My Documents\\file.txt']

Passing Multiple Values

PythonLauncher.bat --files data1.txt data2.txt data3.txt --output results

Python script:

import sys

if "--files" in sys.argv:
    files_idx = sys.argv.index("--files")
    output_idx = sys.argv.index("--output")
    
    # Get all arguments between --files and --output
    files = sys.argv[files_idx + 1:output_idx]
    output = sys.argv[output_idx + 1]
    
    print(f"Files to process: {files}")
    print(f"Output location: {output}")

Using Environment Variables

You can combine environment variables with arguments:

set ENV=production
PythonLauncher.bat --env %ENV% --debug

Python script:

import sys
import os

# Arguments take precedence over environment variables
env = os.getenv("ENV", "development")

if "--env" in sys.argv:
    idx = sys.argv.index("--env")
    env = sys.argv[idx + 1]

print(f"Running in {env} environment")

When to Use Arguments

Use passarguments=1 when:

Your application needs runtime configuration
You’re running the launcher from scripts or shortcuts
You need to pass different parameters for different runs
You’re automating tasks with Task Scheduler or batch scripts

Example automation script:

@echo off
rem daily-backup.bat

echo Running daily backup...
cd C:\Projects\MyApp
PythonLauncher.bat --backup --date %DATE% --notify admin@example.com

if %ERRORLEVEL% EQU 0 (
    echo Backup completed successfully
) else (
    echo Backup failed
)

When to Use Drag and Drop

Use passarguments=0 when:

You need to test different Python files quickly
You’re running utility scripts that don’t need arguments
You want the convenience of dragging files in Windows Explorer
Your scripts are self-contained and don’t need external parameters

See Drag and Drop for more details.

Creating Shortcuts with Arguments

You can create Windows shortcuts with pre-configured arguments:

Right-click PythonLauncher.bat

Select “Create shortcut”

Right-click the shortcut

Select “Properties”

Edit the Target field

Add your arguments after the file path:

"C:\Projects\MyApp\PythonLauncher.bat" --debug --verbose

Rename the shortcut

Give it a descriptive name like “Run App (Debug Mode)”

Now double-clicking the shortcut will always run with those arguments.

Troubleshooting

Arguments Not Received

Check configuration:

set passarguments=1  # Must be 1 to pass arguments

Arguments Treated as Filename

If passarguments=0, the launcher treats the first argument as a file to run:

# With passarguments=0
PythonLauncher.bat --debug
# Tries to run a file named "--debug"

Solution: Set passarguments=1

No Initial File Found

If no initial file exists and passarguments=1, the launcher opens a Python shell:

Python 3.11.5 (tags/v3.11.5:...) on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

Solution: Ensure at least one initial file exists (e.g., run.py, main.py, or app.py)

Arguments with Special Characters

Special characters like &, |, <, > need escaping:

# Wrong
PythonLauncher.bat --query select * from users & exit

# Correct
PythonLauncher.bat --query "select * from users" 

Always quote arguments that contain spaces or special characters.

Quick Reference

Task	Command	Requirement
Pass single argument	`PythonLauncher.bat --debug`	`passarguments=1`
Pass multiple arguments	`PythonLauncher.bat --in data.txt --out result.txt`	`passarguments=1`
Arguments with spaces	`PythonLauncher.bat --msg "Hello World"`	`passarguments=1`
Boolean flags	`PythonLauncher.bat --verbose --debug`	`passarguments=1`
No arguments	Double-click launcher	Either setting

Get Started

Configuration

Usage

Advanced

​The passarguments Configuration

​How It Works

​Configuration Trade-off

​Code Implementation

​Usage Examples

​Example 1: Basic Argument Passing

​Example 2: Configuration File Arguments

​Example 3: Using argparse

​Example 4: Boolean Flags

​Advanced Usage

​Passing Arguments with Spaces

​Passing Multiple Values

​Using Environment Variables

​When to Use Arguments

​When to Use Drag and Drop

​Creating Shortcuts with Arguments

​Troubleshooting

​Arguments Not Received

​Arguments Treated as Filename

​No Initial File Found

​Arguments with Special Characters

​Quick Reference

The passarguments Configuration

How It Works

Configuration Trade-off

Code Implementation

Usage Examples

Example 1: Basic Argument Passing

Example 2: Configuration File Arguments

Example 3: Using argparse

Example 4: Boolean Flags

Advanced Usage

Passing Arguments with Spaces

Passing Multiple Values

Using Environment Variables

When to Use Arguments

When to Use Drag and Drop

Creating Shortcuts with Arguments

Troubleshooting

Arguments Not Received

Arguments Treated as Filename

No Initial File Found

Arguments with Special Characters

Quick Reference