Python: split a list based on a condition?

Question

What\'s the best way, both aesthetically and from a performance perspective, to split a list of items into multiple lists based on a conditional? The equivalent of:

Answer 1

If you don't mind using an external library there two I know that nativly implement this operation:

>>> files = [ ('file1.jpg', 33, '.jpg'), ('file2.avi', 999, '.avi')]
>>> IMAGE_TYPES = ('.jpg','.jpeg','.gif','.bmp','.png')

• iteration_utilities.partition:

  >>> from iteration_utilities import partition
  >>> notimages, images = partition(files, lambda x: x[2].lower() in IMAGE_TYPES)
  >>> notimages
  [('file2.avi', 999, '.avi')]
  >>> images
  [('file1.jpg', 33, '.jpg')]
  

• more_itertools.partition

  >>> from more_itertools import partition
  >>> notimages, images = partition(lambda x: x[2].lower() in IMAGE_TYPES, files)
  >>> list(notimages)  # returns a generator so you need to explicitly convert to list.
  [('file2.avi', 999, '.avi')]
  >>> list(images)
  [('file1.jpg', 33, '.jpg')]