ptcmd

A modern interactive command-line application building library based on prompt_toolkit

Language: English/中文

1. Features

• 🚀 Built on prompt_toolkit for powerful interactive experiences
• 📝 Automatic parameter parsing and completion
• 🌈 Rich text output support (using rich library)
• ⚡ Native async command support
• 🔍 Built-in command completion and shortcut keys

2. Installation

Install from PyPI:

pip install ptcmd

Or install from source:

git clone https://github.com/Visecy/ptcmd.git
cd ptcmd
make install

3. Quick Start

Create a simple command-line application:

import sys
from ptcmd import Cmd

class MyApp(Cmd):
    def do_hello(self, argv: list[str]) -> None:
        """Hello World!"""
        if argv:
            name = argv[0]
        else:
            name = "World"
        self.poutput(f"Hello, {name}!")

if __name__ == "__main__":
    sys.exit(MyApp().cmdloop())

In this basic example:

1. We create a MyApp class inheriting from Cmd
2. Define a do_hello command method
3. The command accepts an optional name parameter
4. Uses "World" if no parameter is provided
5. Output greeting using self.poutput()
6. Start the CLI with cmdloop()

This example demonstrates:

• Command definition syntax
• Parameter handling
• Output display
• Application startup process

Run the program and try the hello command:

(Cmd) hello
Hello, World!
(Cmd) hello Alice
Hello, Alice!

4. Advanced Features

4.1 Auto Argument Parsing

For complex commands, use the auto_argument decorator with type hints for automatic argument parsing:

from ptcmd import Cmd, Arg, auto_argument

class MathApp(Cmd):
    @auto_argument
    def do_add(
        self,
        x: float,
        y: float,
        *,
        verbose: Arg[bool, "-v", "--verbose"] = False
    ) -> None:
        """Add two numbers"""
        result = x + y
        if verbose:
            self.poutput(f"{x} + {y} = {result}")
        else:
            self.poutput(result)

This approach automatically generates equivalent argparse code:

• Converts positional parameters to required arguments
• Converts keyword parameters to optional flags
• Handles type conversion and validation

4.2 Rich Text Output

Leverage rich library for styled output:

class RichApp(Cmd):
    def do_hello(self, argv: list[str]) -> None:
        self.poutput(f"[bold blue]Hello, World![/bold blue]")

For advanced formatting, access the console directly:

class RichApp(Cmd):
    def do_hello(self, argv: list[str]) -> None:
        with self.console.pager(styles=True):
            self.console.print("Hello, World!", style="bold blue")

4.3 Subcommand Support

For command functions that use the automatic parameter parsing feature, ptcmd allows you to add any number of sub-commands to them in a simple way. The execution order of command functions is starting from the root command and then executing them one by one.

1. Single-level subcommand example:

from ptcmd import Cmd, auto_argument

class App(Cmd):
    @auto_argument
    def do_math(self):
        """Math operations"""
        
    @do_math.add_subcommand("add")
    def add(self, x: float, y: float):
        """Addition"""
        self.poutput(f"{x} + {y} = {x + y}")

Usage examples:

(Cmd) math add 5 3
5.0 + 3.0 = 8.0
(Cmd) math sub 5 3
5.0 - 3.0 = 2.0

2. Multi-level subcommand example:

from ptcmd import Cmd, auto_argument

class App(Cmd):
    @auto_argument
    def do_server(self):
        """Server management"""
        
    @do_server.add_subcommand("db")
    def db(self):
        """Database management"""
        
    @db.add_subcommand("migrate")
    def migrate(self, version: str):
        """Execute database migration"""
        self.poutput(f"Migrating to version {version}...")

    @do_server.add_subcommand("cache")
    def cache(self):
        """Cache management"""
        
    @cache.add_subcommand("clear")
    def clear(self, confirm: bool = False):
        """Clear cache"""
        if confirm:
            self.poutput("Cache cleared")
        else:
            self.poutput("Please add --confirm to proceed")

Usage examples:

(Cmd) server db migrate v1.2.0
Migrating to version v1.2.0...
(Cmd) server cache clear --confirm  
Cache cleared

4.4 Async Command Support

Native async/await support for I/O bound operations:

import aiohttp
from ptcmd import Cmd, auto_argument

class AsyncApp(Cmd):
    @auto_argument
    async def do_get(self, url: str):
        """Fetch URL content"""
        async with aiohttp.ClientSession() as session:
            async with session.get(url) as resp:
                self.poutput(await resp.text(), markup=False)

5. Library Comparison

The following table compares the advantages and disadvantages of three libraries: cmd (standard library), cmd2, and ptcmd:

Feature	cmd	cmd2	ptcmd
Feature Richness	Basic	Most Feature-Rich	Moderately Feature-Rich
Learning Curve	Simple	Medium	Medium
Interactive Experience	Basic	Good	Excellent (based on prompt_toolkit)
Auto Completion	None	Supported	Supported
Argument Parsing	Manual Handling	Requires building ArgumentParser	Auto Parsing
Async Support	None	None	Native Support
Rich Text Output	None	Uses cmd2.ansi module	Uses rich library
Dependencies	None	More	Most
Performance	High	Medium	Medium
Use Case	Simple CLI	Complex CLI	Modern CLI

Key Advantages:

• cmd: Python standard library, no dependencies, suitable for simple CLI applications
• cmd2: Comprehensive features, good community support, compatible with cmd, suitable for traditional CLIs requiring rich features
• ptcmd: Provides the best interactive experience, native async support, suitable for modern CLI applications

6. Related Projects

• prompt_toolkit - Foundation for building powerful interactive command lines
• rich - Enables rich text formatting and beautiful output
• typer - Modern CLI framework with type hints
• cmd2 - Inspiration for many ptcmd features
• argparse - Python's standard argument parsing library
• cmd - Python's standard line-oriented command interpreters library

7. Special Thanks

• cmd2 for inspiring the command completion system
• Cline for assisting with project documentation and test cases

8 License

Apache License 2.0 - See LICENSE