argparse-patterns

# argparse-patterns

Python's built-in argparse module for CLI argument parsing - no external dependencies required.

## Overview

Provides comprehensive argparse patterns using only Python standard library. Includes subparsers for nested commands, choices for validation, custom actions, argument groups, and mutually exclusive options.

## Instructions

### Basic Parser Setup

1. Import argparse and create parser with description
2. Add version info with `action='version'`
3. Set formatter_class for better help formatting
4. Parse arguments with `parser.parse_args()`

### Subparsers (Nested Commands)

1. Use `parser.add_subparsers(dest='command')` to create command groups
2. Add individual commands with `subparsers.add_parser('command-name')`
3. Each subparser can have its own arguments and options
4. Nest subparsers for multi-level commands (e.g., `mycli config get key`)

### Choices and Validation

1. Use `choices=['opt1', 'opt2']` to restrict values
2. Implement custom validation with type functions
3. Add validators using argparse types
4. Set defaults with `default=value`

### Actions

1. `store_true/store_false` - Boolean flags
2. `store_const` - Store constant value
3. `append` - Collect multiple values
4. `count` - Count flag occurrences
5. `version` - Display version and exit
6. Custom actions with Action subclass

### Argument Types

1. Positional arguments - Required by default
2. Optional arguments - Prefix with `--` or `-`
3. Type coercion - `type=int`, `type=float`, `type=pathlib.Path`
4. Nargs - `'?'` (optional), `'*'` (zero or more), `'+'` (one or more)

## Available Templates

### Python Templates

- **basic-parser.py** - Simple parser with arguments and options
- **subparser-pattern.py** - Single-level subcommands
- **nested-subparser.py** - Multi-level nested commands (e.g., git config get)
- **choices-validation.py** - Argument choices and validation
- **boolean-flags.py** - Boolean flag patterns
- **custom-actions.py** - Custom action classes
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