How to do multiple imports in Python?

问题:

In Ruby, instead of repeating the "require" (the "import" in Python) word lots of times, I do

%w{lib1 lib2 lib3 lib4 lib5}.each { |x| require x }

So it iterates over the set of "libs" and "require" (import) each one of them. Now I'm writing a Python script and I would like to do something like that. Is there a way to, or do I need to write "import" for all of them.

The straight-forward "traduction" would be something like the following code. Anyway, since Python does not import libs named as strings, it does not work.

requirements = [lib1, lib2, lib3, lib4, lib5]
for lib in requirements:
    import lib

Thanks in advance

回答1:

For known module, just separate them by commas:

import lib1, lib2, lib3, lib4, lib5

If you really need to programmatically import based on dynamic variables, a literal translation of your ruby would be:

modnames = "lib1 lib2 lib3 lib4 lib5".split()
for lib in modnames:
    globals()[lib] = __import__(lib)

Though there's no need for this in your example.

回答2:

Try this:

import lib1, lib2, lib3, lib4, lib5

You can also change the name they are imported under in this way, like so:

import lib1 as l1, lib2 as l2, lib3, lib4 as l4, lib5

回答3:

import lib1, lib2, lib3, lib4, lib5

回答4:

You can import from a string which contains your module name by using the __import__ function.

requirements = [lib1, lib2, lib3, lib4, lib5]
for lib in requirements:
    x = __import__(lib)

回答5:

You can use __import__ if you have a list of strings that represent modules, but it's probably cleaner if you follow the hint in the documentation and use importlib.import_module directly:

import importlib
requirements = [lib1, lib2, lib3, lib4, lib5]
imported_libs = {lib: importlib.import_module(lib) for lib in requirements}

You don't have the imported libraries as variables available this way but you could access them through the imported_libs dictionary:

>>> requirements = ['sys', 'itertools', 'collections', 'pickle']
>>> imported_libs = {lib: importlib.import_module(lib) for lib in requirements}
>>> imported_libs
{'collections': <module 'collections' from 'lib\\collections\\__init__.py'>,
 'itertools': <module 'itertools' (built-in)>,
 'pickle': <module 'pickle' from 'lib\\pickle.py'>,
 'sys': <module 'sys' (built-in)>}

>>> imported_libs['sys'].hexversion
50660592

You could also update your globals and then use them like they were imported "normally":

>>> globals().update(imported_libs)
>>> sys
<module 'sys' (built-in)>