Trace decorator for debugging (Python)

2011-01-24T18:40:51-08:00

Python recipe 577551 by Kevin L. Sitze (classes, debug, debugging, decorators, functions, inspection, modules, trace). Revision 2.

This package provides a decorator for tracing function and method calls in your applications. The tracing capabilities are managed through the logging package, and several mechanisms are provided for controlling the destination of the trace output.

It also provides functionality for adding decorators to existing classes or modules.

Inspect a PYC File (Python)

2011-09-29T20:07:10-07:00

Python recipe 577880 by Eric Snow (bytecode, inspection, pyc). Revision 3.

This is a revamp of a recipe that Ned Batchelder posted on his blog a few years ago (thanks Ned!). That page is pretty insightful, recipe aside.

This recipe works for all versions of Python back to 2.4 (at least). Warning: using one version of Python to inspect a pyc file from another Python version may not work too well.

print variables as a dictionarly (Python)

2009-03-27T07:39:13-07:00

Python recipe 576700 by Maxim Khesin (debugging, inspection, print). Revision 2.

Often I need to print some diagnostic variables and have to construct a format string to include both name and value; but there is a quicker way! This is especially useful for tracing function call values (foo in example below)

Find what class an attribute - ie, myObj.myAttr - comes from, and how it's defined (Python)

2012-10-26T12:59:47-07:00

Python recipe 578305 by Paul Molodowitch (attribute, attributes, class, debugging, inspection, source, __dict__, __getattribute__, __getattr__, __slots__). Revision 3.

When inspecting new code (or when debugging), it can be handy to know exactly where a given attribute on an object or class comes from.

As a simple example, if you have a class MyClass, you might want to know where MyClass().myMethod is defined.

However, things can get tricky when things like __getattr__, __getattribute__, or even compiled objects come into play. That's where this function comes in. It returns what class a given attribute comes from, and what method was used to define it - ie, '__dict__' ('normal' definitions), '__slots__', '__getattr__', '__getattribute__', '(BUILTIN)'.

(Note - this function should't be relied on to be 100% accurate - rather, it's a best guess, for where to look to find it. It takes some pretty infrequent edge cases for it to be wrong, though...)

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