将元素添加到 python 生成器

Question

Is it possible to append elements to a python generator?

I'm currently trying to get all images from a set of disorganized folders and write them to a new directory. To get the files, I'm using os.walk() which returns a list of image files in a single directory. While I can make a generator out of this single list, I don't know how to combine all these lists into one single generator. Any help would be much appreciated.

Related:

• Flattening a shallow list in python

Answer 1

You are looking for itertools.chain . It will combine multiple iterables into a single one, like this:

>>> import itertools 
>>> for i in itertools.chain([1,2,3], [4,5,6]):
...     print(i)
... 
1
2
3
4
5
6

Answer 2

This should do it, where directories is your list of directories:

import os
import itertools

generators = [os.walk(d) for d in directories]
for root, dirs, files in itertools.chain(*generators):
    print root, dirs, files

Answer 3

def files_gen(topdir='.'):
    for root, dirs, files in os.walk(topdir):
        # ... do some stuff with files
        for f in files:
            yield os.path.join(root, f)
        # ... do other stuff

for f in files_gen():
    print f

Answer 4

Like this.

def threeGens( i, j, k ):
    for x in range(i):
       yield x
    for x in range(j):
       yield x
    for x in range(k):
       yield x

Works well.