列表去重的多種方法

python中列表去重

怎么快速的對列表進行去重呢，去重之后原來的順序會不會改變呢？

去重之后順序會改變

set去重

#列表去重改變原列表的順序了
l1 = [1,4,4,2,3,4,5,6,1]
l2 = list(set(l1))
print(l2)    # [1, 2, 3, 4, 5, 6]

但是，可以通過列表中索引（index）的方法保證去重后的順序不變。 

l1 = [1,4,4,2,3,4,5,6,1]
l2 = list(set(l1))
l2.sort(key=l1.index)
print(l2)      # [1, 4, 2, 3, 5, 6]

itertools.groupby

import itertools
l1 = [1,4,4,2,3,4,5,6,1]
l1.sort()
l = []
it = itertools.groupby(l1)
for k,g in it:
    l.append(k)
print(l)      # [1, 2, 3, 4, 5, 6]

fromkeys

l1 = [1,4,4,2,3,4,5,6,1]
t = list({}.fromkeys(l1).keys())
# 解決順序問題
t.sort(key=l1.index)
print(t)         # [1, 4, 2, 3, 5, 6]

通過刪除索引

l1 = [1,4,4,2,3,4,5,6,1]
t = l1[:]
for i in l1:
    while t.count(i) >1:
          del t[t.index(i)]
# 解決順序問題
t.sort(key=l1.index)
print(t)    # [1, 4, 2, 3, 5, 6]

去重不改變順序

建立新列表[]

l1 = [1,4,4,2,3,4,5,6,1]
new_l1 = []
for i in l1:
    if i not in new_l1:
        new_l1.append(i)
print(new_l1)    # [1, 4, 2, 3, 5, 6]

reduce方法

from functools import reduce
l1 = [1,4,4,2,3,4,5,6,1]
func = lambda x,y:x if y in x else x + [y]
print(reduce(func,[[],]+l1))   # [1, 4, 2, 3, 5, 6]