python之常见的坑

li = [1,2,3,4]  # [1,3,4]

# 索引值是奇数的删除

for i in range(4):

    if i % 2 == 1:

        li.pop(i)   # 会报错

print(li)

面试题:

li = [1,2,3,4,5]   #[1,3,4,5]

# 索引值是奇数的删除

for i in range(4):

    if i % 2 == 1:

        li.pop(i)   # 结果不对

print(li)

li = [1,2,3,4,5]

for i in range(len(li)-1,-1,-1):

    if i % 2 == 1:

        li.pop(i)   # 倒序删除

print(li)

偷换感念

li = [1,2,3,4,5]

new_li = []

for i in range(len(li)):

    if i % 2 == 1:

        new_li.append(li[i])

for em in new_li:

    li.remove(em)

print(li)

li = [1,2,3,4,5]

for i in range(len(li)-1,-1,-1):

    if i % 2 == 1:

        del li[i]   # 倒序删除

print(li)

li = [1,2,3,4,5]

del li[1::2]

print(li)

使用for删除列表的时候从左向右删除,会报错.结果不对

dic = {"k1":"v1","k2":"v2"}

for i in dic:

    dic["k3"] = "v3"

print(dic)

面试题:

li = [1,2,3,4]

for i in li:

    li.append(i)

print(li)

不能在遍历字典本身中改变大小,要批量删除字典的键值对

dic = {"k1":"v1","k2":"v2","k3":"v3"}

for i in dic:

    dic["k7"] = "1"

print(dic)

li = []

for i in dic:

    if i == "k1" or i == "k3":

        li.append(i)

for em in li:

    dic.pop(em)

print(dic)
巴特西

python之常见的坑

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