您可能希望使用集合而不是列表。

Python 2.7.3(默认，2014年2月27日，19:58:35)- IPython 1.1.0 - timeit:(github gist)

def diff(a, b):
  b = set(b)
  return [aa for aa in a if aa not in b]

def set_diff(a, b):
  return list(set(a) - set(b))

diff_lamb_hension = lambda l1,l2: [x for x in l1 if x not in l2]

diff_lamb_filter = lambda l1,l2: filter(lambda x: x not in l2, l1)

from difflib import SequenceMatcher
def squeezer(a, b):
  squeeze = SequenceMatcher(None, a, b)
  return reduce(lambda p,q: p+q, map(
    lambda t: squeeze.a[t[1]:t[2]],
      filter(lambda x:x[0]!='equal',
        squeeze.get_opcodes())))

结果:

# Small
a = range(10)
b = range(10/2)

timeit[diff(a, b)]
100000 loops, best of 3: 1.97 µs per loop

timeit[set_diff(a, b)]
100000 loops, best of 3: 2.71 µs per loop

timeit[diff_lamb_hension(a, b)]
100000 loops, best of 3: 2.1 µs per loop

timeit[diff_lamb_filter(a, b)]
100000 loops, best of 3: 3.58 µs per loop

timeit[squeezer(a, b)]
10000 loops, best of 3: 36 µs per loop

# Medium
a = range(10**4)
b = range(10**4/2)

timeit[diff(a, b)]
1000 loops, best of 3: 1.17 ms per loop

timeit[set_diff(a, b)]
1000 loops, best of 3: 1.27 ms per loop

timeit[diff_lamb_hension(a, b)]
1 loops, best of 3: 736 ms per loop

timeit[diff_lamb_filter(a, b)]
1 loops, best of 3: 732 ms per loop

timeit[squeezer(a, b)]
100 loops, best of 3: 12.8 ms per loop

# Big
a = xrange(10**7)
b = xrange(10**7/2)

timeit[diff(a, b)]
1 loops, best of 3: 1.74 s per loop

timeit[set_diff(a, b)]
1 loops, best of 3: 2.57 s per loop

timeit[diff_lamb_filter(a, b)]
# too long to wait for

timeit[diff_lamb_filter(a, b)]
# too long to wait for

timeit[diff_lamb_filter(a, b)]
# TypeError: sequence index must be integer, not 'slice'

@roman-bodnarchuk列表推导函数def diff(a, b)似乎更快。

A = [1,2,3,4]
B = [2,5]

#A - B
x = list(set(A) - set(B))
#B - A 
y = list(set(B) - set(A))

print x
print y 

一个衬套:

diff = lambda l1,l2: [x for x in l1 if x not in l2]
diff(A,B)
diff(B,A)

Or:

diff = lambda l1,l2: filter(lambda x: x not in l2, l1)
diff(A,B)
diff(B,A)

有三种选择，其中两种是可以接受的，另一种不应该这样做。

在较高的级别上，这3个选项是:

减去两组(有时最好) 检查每个列表项是否存在于一个集合中(大多数情况下最好) 检查每个列表项是否存在于列表中(不做)

选项3)永远不应该超过选项2)。根据应用程序的需要，您可能更喜欢选项1)或2)，而在大多数用例中，2)可能是首选方法。2)与1)的性能非常相似，因为两者都具有O(m + n)个时间复杂度。相比之下，2)在空间复杂度上比1)有边际优势，并且既保持了原始列表的顺序，又保持了原始列表中的任何重复。

如果你想删除重复，不关心顺序，那么1)可能是最适合你的。

import time

def fun1(l1, l2):
    # Order and duplications in l1 are both lost, O(m) + O(n)
    return set(l1) - set(l2)

def fun2(l1, l2):
    # Order and duplications in l1 are both preserved, O(m) + O(n)
    l2_set = set(l2)
    return [item for item in l1 if item not in l2_set]

def fun3(l1, l2):
    # Order and duplications in l1 are both preserved, O(m * n)
    # Don't do
    return [item for item in l1 if item not in l2]

A = list(range(7500))
B = list(range(5000, 10000))

loops = 100

start = time.time()
for _ in range(loops):
    fun1(A, B)
print(f"fun1 time: {time.time() - start}")

start = time.time()
for _ in range(loops):
    fun2(A, B)
print(f"fun2 time: {time.time() - start}")

start = time.time()
for _ in range(loops):
    fun3(A, B)
print(f"fun3 time: {time.time() - start}")

fun1 time: 0.03749704360961914
fun2 time: 0.04109621047973633
fun3 time: 32.55076885223389

如果你不关心项目的顺序或重复，请使用set。使用列表推导式:

>>> def diff(first, second):
        second = set(second)
        return [item for item in first if item not in second]

>>> diff(A, B)
[1, 3, 4]
>>> diff(B, A)
[5]
>>>