从列表中有条件地删除项，并通过Python循环从头开始迭代

当条件为true时，我尝试从列表中删除项目，然后从列表的最开始处再次迭代。以下是我的代码：

from random import randint
x = [1,2,3,4,5]

for item in x:
    print("item is " + str(item))
    z = randint(1, 5)
    print("z is " + str(z))
    if z == item:
        x[:] = [item for item in x if item != z]
        print("Remaining list is " + str(x))
    else:
        print("Remaining list is " + str(x))

例如，我在

x

列表中的第一项是1，假设z也是1。当

z==item

时，我的

x

列表将删除第一项（1），并更新为[2,3,4,5]。但我得到以下输出：

item is 1
z is 1
Remaining list is [2, 3, 4, 5]
item is 3
z is 2
Remaining list is [2, 3, 4, 5]

不是从我最近更新的列表[2,3,4,5]中的2重新启动循环，而是从第二个位置3开始循环。每次更新列表时，如何从一开始就重新启动循环？

---

谢谢

您可以在

for

循环之外添加

while

循环，并在删除项目时重新启动

for

循环

from random import randint
x = [1,2,3,4,5]

restart = True

while restart:
    restart = False
    for item in x:
        print("item is " + str(item))
        z = randint(1, 5)
        print("z is " + str(z))
        if z == item:
            x[:] = [item for item in x if item != z]
            print("Remaining list is " + str(x))
            restart = True
            break
        else:
            print("Remaining list is " + str(x))

# results
item is 1
z is 2
Remaining list is [1, 2, 3, 4, 5]
item is 2
z is 2
Remaining list is [1, 3, 4, 5]
item is 1
z is 1
Remaining list is [3, 4, 5]
item is 3
z is 4
Remaining list is [3, 4, 5]
item is 4
z is 3
Remaining list is [3, 4, 5]
item is 5
z is 5
Remaining list is [3, 4]
item is 3
z is 4
Remaining list is [3, 4]
item is 4
z is 1
Remaining list is [3, 4]

---

您可以在

for

循环之外添加

while

循环，并在删除项目时重新启动

for

循环

from random import randint
x = [1,2,3,4,5]

restart = True

while restart:
    restart = False
    for item in x:
        print("item is " + str(item))
        z = randint(1, 5)
        print("z is " + str(z))
        if z == item:
            x[:] = [item for item in x if item != z]
            print("Remaining list is " + str(x))
            restart = True
            break
        else:
            print("Remaining list is " + str(x))

# results
item is 1
z is 2
Remaining list is [1, 2, 3, 4, 5]
item is 2
z is 2
Remaining list is [1, 3, 4, 5]
item is 1
z is 1
Remaining list is [3, 4, 5]
item is 3
z is 4
Remaining list is [3, 4, 5]
item is 4
z is 3
Remaining list is [3, 4, 5]
item is 5
z is 5
Remaining list is [3, 4]
item is 3
z is 4
Remaining list is [3, 4]
item is 4
z is 1
Remaining list is [3, 4]

---

For

循环的工作方式与您期望的不一样，如果您可以在使用条件检查时使用

更好，如下所示：

from random import randint
    x = [1, 2, 3, 4, 5]
    loops = 0
    while loops<len(x):
        item = x[loops]
        print("item is " + str(item))
        z = randint(1, 5)
        print("z is " + str(z))
        if z == item:
            x[:] = [item for item in x if item != z]
            print("Remaining list is " + str(x))
            continue
        else:
            print("Remaining list is " + str(x))
        loops += 1

For
循环的工作方式与您期望的不一样，如果您可以在使用条件检查时使用
更好，如下所示：

from random import randint
    x = [1, 2, 3, 4, 5]
    loops = 0
    while loops<len(x):
        item = x[loops]
        print("item is " + str(item))
        z = randint(1, 5)
        print("z is " + str(z))
        if z == item:
            x[:] = [item for item in x if item != z]
            print("Remaining list is " + str(x))
            continue
        else:
            print("Remaining list is " + str(x))
        loops += 1

在迭代列表时更改列表的大小将导致一系列的off-by-one错误。相反，构建一个新的列表，然后在循环结束时替换旧的列表。在迭代列表时更改列表的大小将导致一系列错误。相反，构建一个新列表，然后在循环结束时替换旧列表。谢谢您的回答！谢谢你的回答！谢谢你的回答！谢谢你的回答！