Eight Practical Python CLI -m Tricks Without Writing Code

Python’s -m option enables powerful one‑liner commands without the need to write scripts; the following eight examples illustrate how to use built‑in modules for common tasks.

0. Python CLI “-m” parameter

Running python --help displays all supported options. The -m mod flag runs a module as a script, allowing immediate use of any module that implements a command‑line interface.

1. Service port testing

Instead of installing telnet , you can use the built‑in telnetlib module to test outbound network ports. Example:

<code>python -m telnetlib -d 142.250.70.174 443</code>

Testing an invalid port (e.g., 999) raises an error, confirming the check.

2. Launch a local web server

Python can start a simple HTTP server without any code:

<code>python -m http.server</code>

The server listens on port 8000 and serves files from the current directory, useful for quickly sharing files with peers.

3. Validate and format a JSON string

Using the json.tool module you can pretty‑print a JSON string directly from the shell:

<code>echo '{"name": {"first_name":"Chris", "last_name":"Tao"}, "age":33}' | python -m json.tool</code>

If the JSON is malformed (e.g., missing a comma), json.tool reports the error, helping you correct it.

4. Create a simple text editor

The idlelib module (based on Tkinter) can launch a minimal UI editor:

<code>mkdir get_time_app && python -m idlelib get_time_app/print_time.py</code>

After editing and saving (Ctrl+S), you can view the file with cat get_time_app/print_time.py .

5. Build an executable application

Python’s built‑in zipapp module packages a directory into a self‑contained .pyz executable:

<code>python -m zipapp get_time_app -m "print_time:main"</code>

Run the resulting application with python get_time_app.pyz .

6. Encode and decode strings or files

For quick encoding, use the encodings.rot_13 module:

<code>echo "I am Chris" | python -m encodings.rot_13</code>

Base64 encoding/decoding is also available via the base64 module:

<code>echo "I am Chris" | python -m base64</code>

<code>echo "SSBhbSBDaHJpcwo=" | python -m base64 -d</code>

Files can be encoded similarly, and the decoded script can be executed directly.

7. Retrieve system metadata

Running python -m sysconfig prints comprehensive build and configuration information. For a concise view of the environment and site‑packages paths, use:

<code>python -m site</code>

8. File compression

The zipfile module can create and extract ZIP archives without external tools:

<code>python -m zipfile -c get_time_app.zip get_time_app</code>

<code>python -m zipfile -e get_time_app.zip get_time_app_extracted</code>

After extraction, you can verify the contents with ls and cat . The module also supports TAR and GZIP formats.

Summary

The article showcases how Python’s built‑in modules accessed via the -m flag can accomplish a wide range of tasks without writing any code, offering convenient shortcuts for developers in many scenarios.