Python module and all

Question

I trying to understand how to manage module with __all. For example, I have following structured code:

main.py |=> /database |=> __init__.py |=> engine (with variables engine, session, etc.)

now I want to be able to import session and engine instances directly from database module like:

from database import session

I tried to add line __all__ = ['session'] or __all__ = ['engine.session'] to __init__py but when I trying to do import I've got an exception AttributeError: 'modile' object has not attribute 'engine.session'.

Is there any way to achieve wanted behavior?

Martijn Pieters · Accepted Answer · 2013-06-21 13:49:04Z

5

Listing names in __all__ does not, by itself, import items into a module. All it does is list names to import from that module if you used from database import * syntax.

Import session into database/__init__.py:

from .engine import session

answered Jun 21, 2013 at 13:49

Martijn Pieters

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3 Comments

Alex G.P. Over a year ago

Thank you for solution, but I still have a question - if I importting all required classes/functions/variables in __init__.py I can do not bother about filling __all__ - all I imported already available. So, what which reasons to use __all__?

Martijn Pieters Over a year ago

@AlexG.P.: use __all__ to flag what names are 'importable'; if someone does from database import * only names listed in __all__ will be imported, rather than all names in the namespace of the module.

Alex G.P. Over a year ago

Ahh, it only can descrease ramges of imported types, but not increase it. Great thanks.

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