What does mean __all__ = [ ... ]?

Question

I've seen this constuction into Scrapy framework sources: https://github.com/scrapy/scrapy/blob/master/scrapy/exporters.py#L16-L18

Answer 1

It's defining the modules (items) of a package (module) that get imported when you do:

from package import *
from module import *

See https://docs.python.org/2/tutorial/modules.html#importing-from-a-package for details.