for循環刪除list裏面的某項數據會出錯

方法-倒着刪除 正向刪除會跳過刪除項後面一個

l = [1, 2, 3, 3, 5, 6]
for i in l:
    print(i)
    if i == 3:
        l.remove(i)
    print(l)

結果:
1
[1, 2, 3, 3, 5, 6]
2
[1, 2, 3, 3, 5, 6]
3
[1, 2, 3, 5, 6]
5
[1, 2, 3, 5, 6]
6
[1, 2, 3, 5, 6]
倒循環刪除:

list1 = [1,2,3,4,4,5,6]
for i in reversed(list1):
    if i == 4:
        list1.remove(i)
        print("刪除:",i)
    print(i)
for i in list1:
    print(i)

備用方法:

list1 = [1, 2, 3, 3, 4, 4, 5, 6, 6, 6, 7, 8, 9]
list2 = list(set(list1))
print(list2)
list1 = [1, 2, 3, 3, 4, 4, 5, 6, 6, 6, 7, 8, 9]
list2=[]
for i in list1:
    if not i in list2:
        list2.append(i)
print(list2)