Python's Missing Debug Print Command

0.12.2 · active · verified Sat Apr 11

devtools provides an enhanced debug print command for Python, offering formatted output with file, line number, function information, and variable names. It's designed to be more readable than the standard `print()` function, especially for complex data structures. The library is actively maintained, with its current version being 0.12.2, and has a consistent release cadence.

Warnings

breaking `Pygments` became a mandatory dependency in `v0.12.0` (August 2023). Environments that previously used `devtools` without `Pygments` installed (and thus without syntax highlighting) will now require `Pygments` for successful installation.
Fix: Ensure `pygments` is included in your project's dependencies: `pip install devtools pygments`.
gotcha The `debug()` function returns its arguments. If a single non-keyword argument is passed, it returns that argument. If multiple arguments are passed (positional or keyword), they are returned as a tuple (with a dictionary for kwargs). This differs from `print()` which always returns `None`.
Fix: Be mindful when using `debug()` in expressions or assignments, as its return value might be unexpectedly captured. Example: `val = debug(my_var)` will assign `my_var` to `val`.
gotcha The `debug.install()` method, intended to add `debug` to `__builtins__` for usage without explicit import, does not directly modify your Python environment. Instead, it prints instructions for you to manually create or edit a `sitecustomize.py` file.
Fix: Run `python -m devtools install` and follow the printed instructions to configure `sitecustomize.py` if you wish to use `debug()` without importing it.
breaking Python-devtools does not currently support Python 3.13, which can lead to unexpected behavior or errors if used with this version.
Fix: Avoid using `devtools` with Python 3.13. Check the official documentation for updates on 3.13 compatibility.

Install

pip install devtools Install latest version

Imports

debug
```
from devtools import debug
```
The primary way to use the debug function. While `debug.install()` can add `debug` to builtins, it requires manual configuration of `sitecustomize.py`.

Quickstart

This quickstart demonstrates the core `debug()` function to print variables, expressions, and complex data structures with enhanced formatting, including file, line number, and function context. It shows usage with simple variables, lists, function arguments, and class attributes.

from devtools import debug

def example_function(a, b):
    result = a * b
    debug(a, b, result)
    return result

my_list = [1, 2, {'key': 'value', 'nested': [3, 4]}]
debug(my_list)

example_function(10, 5)

class MyClass:
    def __init__(self, name):
        self.name = name
        self.data = {'id': 123, 'status': 'active'}

obj = MyClass('TestObject')
debug(obj.name, obj.data)

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