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  <meta name="description"
        content="Chapter 22 of Python Zero to Hero: build robust command-line interfaces with argparse, Click and Typer."/>
  <meta name="keywords"
        content="Python, CLI, command line, argparse, click, typer, console scripts, CLI tools"/>
  <meta name="author" content="Luca Bocaletto"/>
  <title>Chapter 22 – Building CLI Tools with argparse, Click & Typer | Python Zero to Hero</title>

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  <!-- Main Content -->
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    <header class="my-4">
      <h1 class="display-6">Chapter 22: Building CLI Tools with argparse, Click &amp; Typer</h1>
      <p class="text-muted">
        Learn to create powerful command-line interfaces using Python’s standard library and popular frameworks.
      </p>
      <a href="src/chapter22.py" download class="btn btn-outline-primary btn-sm btn-py">
        Download <code>chapter22.py</code>
      </a>
      <hr>
    </header>

    <!-- Objectives -->
    <section id="objectives" class="mb-5">
      <h2>Objectives</h2>
      <ul>
        <li>Use <code>argparse</code> to parse arguments and options.</li>
        <li>Create commands and subcommands with <code>Click</code>.</li>
        <li>Leverage <code>Typer</code> and type hints to build CLIs.</li>
        <li>Package your tool as a console script.</li>
        <li>Handle input validation, help text and error messages.</li>
      </ul>
    </section>

    <!-- 1. argparse Basics -->
    <section id="argparse" class="mb-5">
      <h2>1. argparse Basics</h2>
      <pre><code class="python">import argparse

def main():
    parser = argparse.ArgumentParser(description="Greet a user.")
    parser.add_argument("name", help="Name of the user")
    parser.add_argument("-t", "--times", type=int, default=1,
                        help="Number of greetings")
    args = parser.parse_args()

    for _ in range(args.times):
        print(f"Hello, {args.name}!")

if __name__ == "__main__":
    main()</code></pre>
      <p>Run: <code>python chapter22.py Alice -t 3</code></p>
    </section>

    <!-- 2. Click Library -->
    <section id="click" class="mb-5">
      <h2>2. Click</h2>
      <pre><code class="python">import click

@click.command()
@click.argument("name")
@click.option("--times", default=1, help="Number of greetings")
def cli(name, times):
    """Greet a user multiple times."""
    for _ in range(times):
        click.echo(f"Hello, {name}!")

if __name__ == "__main__":
    cli()</code></pre>
      <p>Install: <code>pip install click</code>. Run: <code>python chapter22.py Bob --times 2</code></p>
    </section>

    <!-- 3. Typer Framework -->
    <section id="typer" class="mb-5">
      <h2>3. Typer &amp; Type Hints</h2>
      <pre><code class="python">import typer

app = typer.Typer()

@app.command()
def greet(name: str, times: int = 1):
    \"\"\"Greet a user multiple times.\"\"\"
    for _ in range(times):
        typer.echo(f"Hello, {name}!")

if __name__ == "__main__":
    app()</code></pre>
      <p>Install: <code>pip install typer[all]</code>. Run: <code>python chapter22.py greet Carol --times 3</code></p>
    </section>

    <!-- 4. Packaging as Console Script -->
    <section id="packaging" class="mb-5">
      <h2>4. Packaging CLI Tools</h2>
      <p>Add to <code>setup.py</code> or <code>pyproject.toml</code>:</p>
      <pre><code class="toml">[project.scripts]
mycli = "mypackage.cli:app"</code></pre>
      <p>After installation: <code>mycli --help</code></p>
    </section>

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      <h2>Exercises</h2>
      <ol>
        <li>Extend the <code>argparse</code> example with a <code>--uppercase</code> flag.</li>
        <li>Create a Click group with two subcommands: <code>greet</code> and <code>farewell</code>.</li>
        <li>Build a Typer app with commands to add/list/remove items from an in-memory todo list.</li>
        <li>Package the Typer app and install it locally as <code>todo-cli</code>.</li>
      </ol>
    </section>

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