Python對list去重的各種方法
阿新 • • 發佈:2018-12-10
參考原文:https://www.the5fire.com/python-remove-duplicates-in-list.html
需求:去list進行去重,去重後保證順序不變
方法1:for迴圈
ids = [1, 2, 3, 3, 4, 2, 3, 4, 5, 6, 1]
new_ids = []
for id in ids:
if id not in new_ids:
new_ids.append(id)
print("new_ids==>", new_ids)
方法2:set
ids = [1,4,3,3,4,2,3,4,5,6,1] new_ids = list(set(ids)) print(new_ids)
測試發現去重後不能保證原來的順序
方法3:按照索引再次排序
ids = [1, 4, 3, 3, 4, 2, 3, 4, 5, 6, 1]
new_ids = list(set(ids))
new_ids.sort(key=ids.index)
print(new_ids)
方法4:用reduce
ids = [1,4,3,3,4,2,3,4,5,6,1]
func = lambda x,y:x if y in x else x + [y]
reduce(func, [[], ] + ids)
[1, 4, 3, 2, 5, 6]
其中的 lambda x,y:x if y in x else x + [y] 等價於 lambda x,y: y in x and x or x+[y] 。
思路其實就是先把ids變為[[], 1,4,3,......] ,然後在利用reduce的特性