我在Python中有两个列表:

temp1 = ['One', 'Two', 'Three', 'Four']
temp2 = ['One', 'Two']

假设每个列表中的元素都是唯一的,我想用第一个列表中的项创建第三个列表,这些项不在第二个列表中:

temp3 = ['Three', 'Four']

有没有没有周期和检查的快速方法?


当前回答

我在这个游戏中有点晚了,但你可以做一个性能的比较,上面提到的一些代码和这个,两个最快的竞争者是,

list(set(x).symmetric_difference(set(y)))
list(set(x) ^ set(y))

我为我的初级编码水平道歉。

import time
import random
from itertools import filterfalse

# 1 - performance (time taken)
# 2 - correctness (answer - 1,4,5,6)
# set performance
performance = 1
numberoftests = 7

def answer(x,y,z):
    if z == 0:
        start = time.clock()
        lists = (str(list(set(x)-set(y))+list(set(y)-set(y))))
        times = ("1 = " + str(time.clock() - start))
        return (lists,times)

    elif z == 1:
        start = time.clock()
        lists = (str(list(set(x).symmetric_difference(set(y)))))
        times = ("2 = " + str(time.clock() - start))
        return (lists,times)

    elif z == 2:
        start = time.clock()
        lists = (str(list(set(x) ^ set(y))))
        times = ("3 = " + str(time.clock() - start))
        return (lists,times)

    elif z == 3:
        start = time.clock()
        lists = (filterfalse(set(y).__contains__, x))
        times = ("4 = " + str(time.clock() - start))
        return (lists,times)

    elif z == 4:
        start = time.clock()
        lists = (tuple(set(x) - set(y)))
        times = ("5 = " + str(time.clock() - start))
        return (lists,times)

    elif z == 5:
        start = time.clock()
        lists = ([tt for tt in x if tt not in y])
        times = ("6 = " + str(time.clock() - start))
        return (lists,times)

    else:    
        start = time.clock()
        Xarray = [iDa for iDa in x if iDa not in y]
        Yarray = [iDb for iDb in y if iDb not in x]
        lists = (str(Xarray + Yarray))
        times = ("7 = " + str(time.clock() - start))
        return (lists,times)

n = numberoftests

if performance == 2:
    a = [1,2,3,4,5]
    b = [3,2,6]
    for c in range(0,n):
        d = answer(a,b,c)
        print(d[0])

elif performance == 1:
    for tests in range(0,10):
        print("Test Number" + str(tests + 1))
        a = random.sample(range(1, 900000), 9999)
        b = random.sample(range(1, 900000), 9999)
        for c in range(0,n):
            #if c not in (1,4,5,6):
            d = answer(a,b,c)
            print(d[1])

其他回答

我想要一个能够使用两个列表并能做diff in bash所做的事情的东西。因为当你搜索“python diff two lists”时,这个问题首先会弹出,而且不是很具体,所以我会把我想到的贴出来。

使用difflib中的SequenceMather,你可以像diff一样比较两个列表。其他答案都不会告诉你差异发生的位置,但这个答案可以。有些答案只给出了一个方向上的差异。有些元素会重新排序。有些公司不处理副本。但是这个解决方案让你在两个列表之间有了真正的区别:

a = 'A quick fox jumps the lazy dog'.split()
b = 'A quick brown mouse jumps over the dog'.split()

from difflib import SequenceMatcher

for tag, i, j, k, l in SequenceMatcher(None, a, b).get_opcodes():
  if tag == 'equal': print('both have', a[i:j])
  if tag in ('delete', 'replace'): print('  1st has', a[i:j])
  if tag in ('insert', 'replace'): print('  2nd has', b[k:l])

这个输出:

both have ['A', 'quick']
  1st has ['fox']
  2nd has ['brown', 'mouse']
both have ['jumps']
  2nd has ['over']
both have ['the']
  1st has ['lazy']
both have ['dog']

当然,如果您的应用程序做出了与其他答案相同的假设,那么您将从中受益最大。但如果你正在寻找一个真正的差异功能,那么这是唯一的方法。

例如,其他答案都无法处理:

a = [1,2,3,4,5]
b = [5,4,3,2,1]

但这一个有:

  2nd has [5, 4, 3, 2]
both have [1]
  1st has [2, 3, 4, 5]

我们可以计算交集减去列表并集:

temp1 = ['One', 'Two', 'Three', 'Four']
temp2 = ['One', 'Two', 'Five']

set(temp1+temp2)-(set(temp1)&set(temp2))

Out: set(['Four', 'Five', 'Three']) 

我更喜欢使用转换到集,然后使用“差分()”函数。完整的代码是:

temp1 = ['One', 'Two', 'Three', 'Four'  ]                   
temp2 = ['One', 'Two']
set1 = set(temp1)
set2 = set(temp2)
set3 = set1.difference(set2)
temp3 = list(set3)
print(temp3)

输出:

>>>print(temp3)
['Three', 'Four']

这是最容易理解的,而且在将来,如果你处理大型数据,将其转换为集合将删除不需要的重复项。希望能有所帮助;-)

最简单的方法,

使用设置().difference(设置())

list_a = [1,2,3]
list_b = [2,3]
print set(list_a).difference(set(list_b))

答案设置([1])

可以打印为列表,

print list(set(list_a).difference(set(list_b)))

试试这个:

temp3 = set(temp1) - set(temp2)