How to set up collection of Python Classes with inter-dependency?

Question

So I have a set of .py documents as follows:

/Spider
  Script.py
  /Classes
    __init__.py
    ParseXML.py
    CrawlWeb.py
    TextAnalytics.py

Each .py document in the /Classes subfolder contains a class for a specific purpose, the script schedules the different components. There are a couple of questions I had:

1) A lot of the classes share frameworks such as urllib2, threading etc. What is considered the 'best' form for setting up the import statements? I.e. is there a way for me to use something like the __init__.py file to pass the shared dependencies to all of the classes, then use the specific .py files to import the singular dependencies?

2) Some of the classes call on the other classes, (e.g. the CrawlWeb.py document uses the ParseXML class to update the XML files after crawling). I separated out the classes like this because they were each quite large and so were easier to update like this... Would it be considered best form to combine classes in this case or are there other ways to get round this?

The classes will only ever be used as part of the script. So far the only real solution I've been able to come up with is perhaps using the Script.py file for all of the import statements, but it seems a little bit messy. Any advice would be very appreciated.

Answer 1

1. The best way to handle the common imports is to import them in each module they're used. While this probably feels annoying to you because you have to type more, it makes it dramatically clearer to the reader of the code what modules are in scope. You're not missing something by doing common imports; you're doing it right.
2. While you certainly can put your classes all into separate files, it's more common in Python to group related classes together in a single module. Given how short it sounds like your script is, that may mean it makes sense for you to pull everything into a single file. This is a judgment call, and I cannot offer a hard-and-fast rule.