how to interleaving lists [duplicate]

问题:

This question already has an answer here:

• How to elegantly interleave two lists of uneven length in python? 7 answers

I have two lists that could be not equal in lengths and I want to be able to interleave them. I want to be able to append the extra values in the longer list at the end of my interleaved list.I have this:

def interleave(xs,ys):
a=xs
b=ys
minlength=[len(a),len(b)]
extralist= list()
interleave= list()
for i in range((minval(minlength))):
    pair=a[i],b[i]
    interleave.append(pair)
    flat=flatten(interleave)
    c=a+b
if len(b)>len(a):
    remainder=len(b)-len(a)
    print(remainder)
    for j in range(remainder,-1,-1):
        extra=b[-j]
        extralist.append(extra)
        print(extralist)
if len(a)>len(b):
    remainder=len(a)-len(b)
    print(remainder)
    for j in range(remainder,-1,-1):
        extra=a[-j]
        extralist.append(extra)
final=flat+extralist
return final

but if I test it:

>>> interleave([1,2,3], ["hi", "bye",True, False, 33])
[1, 'hi', 2, 'bye', 3, True]
>>> 

The False and 33 don't appear. What is it that Im doing wrong?

EDIT: I found the solution to it. I indexed backwards :)

回答1:

Here is a solution using itertools.zip_longest and a list comprehension:

>>> from itertools import zip_longest
>>> a = [1, 2, 3]
>>> b = ["hi", "bye", True, False, 33]
>>> [y for x in zip_longest(a, b) for y in x]
[1, 'hi', 2, 'bye', 3, True, None, False, None, 33]
>>> [y for x in zip_longest(a, b) for y in x if y is not None]
[1, 'hi', 2, 'bye', 3, True, False, 33]
>>>

---

Edit:

If you don't want to use itertools, I guess you could do:

>>> a = [1, 2, 3]
>>> b = ["hi", "bye", True, False, 33]
>>> items = sorted((a,b), key=len)
>>> out = []
>>> for x,y in enumerate(items[1]):
...     out.append(y)
...     try:
...         out.append(items[0][x])
...     except IndexError:
...         out.extend(items[1][x+1:])
...         break
...
>>> out
['hi', 1, 'bye', 2, True, 3, False, 33]
>>>

But I must say this method isn't as efficient as my first solution.

---

Edit 2:

Changing enumerate to zip reduces the efficiency again. However, if you must, then you can do this:

>>> a = [1, 2, 3]
>>> b = ["hi", "bye", True, False, 33]
>>> out = []
>>> items = sorted((a,b), key=len)
>>> for x,y in zip(range(len(items[1])), items[1]):
...     out.append(y)
...     try:
...         out.append(items[0][x])
...     except IndexError:
...         out.extend(items[1][x+1:])
...         break
...
>>> out
['hi', 1, 'bye', 2, True, 3, False, 33]
>>>

回答2:

Another option

from itertools import chain
x = [1, 2, 3]
y = iter(["hi", "bye",True, False, 33])
list(chain.from_iterable(zip(x, y))) + list(y)
[1, 'hi', 2, 'bye', 3, True, False, 33]