[Python-ideas] PEP x: Static module/package inspection

anatoly techtonik techtonik at gmail.com
Wed Dec 28 11:15:24 CET 2011

(reposting this from Google Group once more as the previous post missed 
Mailing List, because I was not subscribed in Mailman)

*Static module/package inspection*

 - static: without execution (as opposed to dynamic)
 - module/package: .py or __init__.py file
 - inspection: get an overview of the contents

*What should this do?*
The proposal to add a mechanism to Python interpreter to get an outline of 
module/package contents without importing or executing module/package. The 
outline includes names of classes, functions, variables. It also should 
contain values for variables that could be provided without sophisticated 
calculations (e.g. a string, integer, but probably not expressions as it 
may lead to security leaks).

*user story PEPx.001:*
As a Python package maintainer, I find it bothersome to repeatedly write 
bolierplate code (e.g. setup.py) to package my single file module. The 
reason I should write setup.py is to provide version and description info. 
This info is already available in my module source code. So I need to 
either copy/paste the info from the module manually, or to import (and 
hence execute) my module during packaging and installation, which I don't 
want either, because modules are often installed with root privileges.

With this PEP, packing tool will be able to extract meta information from 
my module without executing it or without me manually copying version 
fields into some 'package configuration file'.

*user story PEPx.002:*
As a Python Application developer, I find it really complicated to provide 
plugin extension subsystem for my users. Users need a mechanism to switch 
between different versions of the plugin, and this mechanism is usually 
provided by external tool such as setuptools to manage and install multiple 
versions of plugins in local Python package repository. It is rather hard 
to create an alternative approach, because you are forced to maintain 
external meta-data about your plugin modules even in case it is already 
available inside the module.

With this PEP, Python Application will be able to inspect 
meta-data embedded inside of plugins before choosing which version to load. 
This will also provide a standard mechanism for applications to check 
modules returned by packaging tools without executing them. This will 
greatly simplify writing and debugging custom plugins loaders on different 

*Feedback goal*
At this stage I'd like to a community response to two separate questions:
1. If everybody feels this functionality will be useful for Python
2. If the solution is technically feasible

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