questions about dir and import in python

Question

I have some questions about Python's dir function

>>>import urllib
>>>dir(urllib)
['__builtins__', '__cached__', '__doc__', '__file__','__loader__','__name__','__package__', '__path__', '__spec__']

And when I do like this

>>>import urllib.request
>>>dir(urllib)
['__builtins__', '__cached__', '__doc__', '__file__', '__loader__', '__name__','__package__', '__path__', '__spec__', 'error', 'parse', 'request', 'response']

Why it comes three more attributes? Why the request attribute doesn't in the dir(urllib) at first?

I' really appriciate your help!

Answer 1

urllib is a package, whereas in urllib.request , request is a module inside the urllib package.

When you import a package, it does not automatically import modules inside the package, unless that module is imported by the __init__.py for that package.

But the __init__.py of urllib is empty (its empty in my Python 3.4 ) , and hence when simply importing urllib it does not import the module urllib.request .