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Exploring Python’s Hidden CLI Modules

| python | thoughts |

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Note: I am referring to the Python version 3.13.

Intro

TL;DR: Python’s standard library includes a surprising number of CLI tools—some helpful, some quirky. Here’s a categorized list worth exploring.

If you’ve used Python for a while, you’ve probably come across modules that can be run directly from the command line. The most well-known is probably venv, but others like http.server, uuid, json.tool, and unittest have been lifesavers for me.

Python is famous for its “batteries included” philosophy. With a standard library this rich, I started wondering: how many modules actually offer a command-line interface? Turns out, quite a few - and you don’t need to scrape the CPython repo to find them. The official documentation lists them neatly.

This post is just a curiosity-driven dive into those CLI-enabled modules, grouped into:

  • General-Purpose Tools
  • Python-Specific Tools
  • Documentation & Introspection
  • Educational / Easter Egg

Some are useful. Some are weird. All are built in.

Modules

General-Purpose Tools

file, network, compression, system utilities

Module Sample CLI Usage Details
base64 echo "hello" \| base64
echo aGVsbG8K \| python3 -m base64 -d		 Encode/decode Base64. Useful for encoding binary data as ASCII text, e.g., for email or HTTP transmission.
calendar python3 -m calendar 2025 Print yearly calendar. Great for quick calendar checks in the terminal.
difflib python3 -m difflib file1.py file2.py Show file differences. Unified diff format helps visualize changes in code or text.
filecmp python3 -m filecmp dir1 dir2 Compare files/directories. Useful for checking duplicates or sync issues.
fileinput python3 -m fileinput file1.txt file2.txt Read from multiple files. Treats multiple inputs as a single stream—ideal for batch processing.
ftplib python3 -m ftplib ftp.example.com Interactive FTP session. Helpful for manual file transfers or protocol debugging.
gzip python3 -m gzip -d file.txt.gz
python3 -m gzip file.txt		 Compress/decompress .gz files. Lightweight alternative to external tools.
http.server python3 -m http.server 8000 Simple HTTP server. Great for serving static files during local development.
json.tool cat data.json \| python3 -m json.tool Pretty-print/validate JSON. Helpful for debugging API responses and config files.
mimetypes python3 -m mimetypes file.jpg Guess file MIME type. Useful in web or file server contexts.
platform python3 -m platform Show system/platform info. Get OS, architecture, and Python version details.
poplib python3 -m poplib Interact with POP3 email. Mainly educational or for low-level debugging.
quopri echo "hello=0Aworld=" \| python3 -m quopri -d Encode/decode quoted-printable. Commonly used in email transfer encoding.
random python3 -m random Generate random number. Outputs a random float between 0 and 1.
sqlite3 python3 -m sqlite3
sqlite> SELECT sqlite_version();		 SQLite CLI shell. Lightweight database querying without extra tools.
tarfile python3 -m tarfile -c archive.tar file1 file2
python3 -m tarfile -l archive.tar		 Create/list .tar files. Use Python to manage tar archives.
timeit python3 -m timeit "'-'.join(str(n) for n in range(100))" Benchmark small code snippets. Useful for quick performance checks.
uuid python3 -m uuid Generate UUID. Create unique identifiers for systems or databases.
webbrowser python3 -m webbrowser https://example.com Open URLs in browser. Automate browser launches from scripts.
zipfile python3 -m zipfile -c archive.zip file1 file2
python3 -m zipfile -l archive.zip		 Create/list ZIP files. Handle ZIP archives without needing external utilities.

These built-in modules can be handy on systems where only Python is available.

Python-Specific Tools

development, testing, packaging, debugging

Module Purpose
asyncio Async event loop and coroutine support
code Launch interactive Python shell
compileall Compile all .py files to .pyc bytecode
cProfile / profile Performance profiling of Python programs
dis Disassemble Python bytecode
encodings.rot_13 ROT13 codec (Python-specific codec example)
ensurepip Bootstrap pip installation
idlelib Launch the IDLE development environment
json.tool Pretty-print and validate JSON
pdb Python debugger
pickle / pickletools Serialize and inspect Python objects
py_compile Compile Python source to bytecode
runpy Run Python modules as scripts
site Site-specific configuration hook for Python
sysconfig Access Python build configuration info
tabnanny Detect indentation errors in Python source files
tokenize Convert Python source code into tokens
trace Trace program execution, function calls
unittest Run unit tests
venv Create isolated Python environments
zipapp Package Python apps into executable ZIPs

Documentation & Introspection Tools

auto-generating or validating Python docs

Module Purpose
pydoc Generate/view Python docstrings in text/HTML
doctest Test examples embedded in docstrings
inspect Introspect live objects for signatures, source, etc.
pyclbr Class browser support via introspection
ast Parse and analyze abstract syntax trees
symtable Analyze symbol tables used by the compiler

Educational / Easter Egg

Module Purpose
antigravity Open XKCD comic. Launches a browser to the classic XKCD comic #353
this The Zen of Python
turtledemo Demos for turtle graphics module

Thoughts

You might be wondering why all these CLI interfaces exist in the first place. Python’s core team values backward compatibility, and although some outdated modules are gradually being removed (see PEP 594 and PEP 632), a lot of legacy code remains.

Back in the early days of Python, the interpreter came with a large set of useful modules. This was often referred to as “batteries included” philosophy and was one of the cornerstones to Python’s success story. Users didn’t have to figure out how to download and install separate packages in order to write a simple web server or parse email.

Today, this legacy can feel bloated, but it’s also part of what made Python so approachable and powerful. The good news is, with ongoing cleanup efforts, the standard library is becoming more maintainable and less painful for core contributors.

In the meantime, these built-in CLI tools are still worth knowing about. Especially if you’re working in a minimal environment where installing extra tools isn’t an option.

References

Bonus: Packages I’d Remove Tomorrow

Here’s my personal hit list of packages I believe should be deprecated and removed as soon as possible from the standard library:

  1. tkinter — GUI toolkit with a dated feel and platform inconsistencies.
  2. turtledemo — Educational, but better suited as a pip-installable package or separate teaching tool.
  3. idlelib — Underused legacy IDE; doesn’t belong in the core distribution anymore.
  4. xmlrpc — Outdated protocol, mostly replaced by REST or gRPC in modern projects.