这三种从列表中删除元素的方法有什么区别吗?
>>> a = [1, 2, 3]
>>> a.remove(2)
>>> a
[1, 3]
>>> a = [1, 2, 3]
>>> del a[1]
>>> a
[1, 3]
>>> a = [1, 2, 3]
>>> a.pop(1)
2
>>> a
[1, 3]
这三种从列表中删除元素的方法有什么区别吗?
>>> a = [1, 2, 3]
>>> a.remove(2)
>>> a
[1, 3]
>>> a = [1, 2, 3]
>>> del a[1]
>>> a
[1, 3]
>>> a = [1, 2, 3]
>>> a.pop(1)
2
>>> a
[1, 3]
当前回答
下面是一个详细的答案。
Del可用于任何类对象,而pop和remove可用于特定类。
为del
下面是一些例子
>>> a = 5
>>> b = "this is string"
>>> c = 1.432
>>> d = myClass()
>>> del c
>>> del a, b, d # we can use comma separated objects
我们可以在用户创建的类中重写__del__方法。
具体用途与列表
>>> a = [1, 4, 2, 4, 12, 3, 0]
>>> del a[4]
>>> a
[1, 4, 2, 4, 3, 0]
>>> del a[1: 3] # we can also use slicing for deleting range of indices
>>> a
[1, 4, 3, 0]
为流行
Pop将索引作为参数,并删除该索引处的元素
与del不同,当在list object上调用pop时,返回该下标处的值
>>> a = [1, 5, 3, 4, 7, 8]
>>> a.pop(3) # Will return the value at index 3
4
>>> a
[1, 5, 3, 7, 8]
为消除
Remove获取参数值并从列表中删除该值。
如果存在多个值,则删除第一个值
注意:如果该值不存在,将抛出ValueError
>>> a = [1, 5, 3, 4, 2, 7, 5]
>>> a.remove(5) # removes first occurence of 5
>>> a
[1, 3, 4, 2, 7, 5]
>>> a.remove(5)
>>> a
[1, 3, 4, 2, 7]
希望这个答案对你有帮助。
其他回答
列表上的删除操作给定一个要删除的值。它搜索列表以查找具有该值的项,并删除找到的第一个匹配项。如果没有匹配项,则是一个错误,引发ValueError。
>>> x = [1, 0, 0, 0, 3, 4, 5]
>>> x.remove(4)
>>> x
[1, 0, 0, 0, 3, 5]
>>> del x[7]
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
del x[7]
IndexError: list assignment index out of range
del语句可用于删除整个列表。如果你有一个特定的列表项作为del的参数(例如listname[7]专门引用列表中的第8项),它会删除该项。甚至可以从列表中删除“slice”。如果索引超出范围,则会引发IndexError。
>>> x = [1, 2, 3, 4]
>>> del x[3]
>>> x
[1, 2, 3]
>>> del x[4]
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
del x[4]
IndexError: list assignment index out of range
The usual use of pop is to delete the last item from a list as you use the list as a stack. Unlike del, pop returns the value that it popped off the list. You can optionally give an index value to pop and pop from other than the end of the list (e.g listname.pop(0) will delete the first item from the list and return that first item as its result). You can use this to make the list behave like a queue, but there are library routines available that can provide queue operations with better performance than pop(0) does. It is an error if there index out of range, raises a IndexError.
>>> x = [1, 2, 3]
>>> x.pop(2)
3
>>> x
[1, 2]
>>> x.pop(4)
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
x.pop(4)
IndexError: pop index out of range
有关更多细节,请参阅collections.deque。
使用del按索引删除元素,使用pop()按索引删除元素(如果需要返回值),使用remove()按值删除元素。最后一个需要搜索列表,如果列表中没有这样的值,则引发ValueError。
当从一个包含n个元素的列表中删除索引i时,这些方法的计算复杂度为
del O(n - i)
pop O(n - i)
remove O(n)
del、pop和remove在执行速度上的差异:
当移除任何中间项目时:
import timeit
print(timeit.timeit("a=[1,2,3,4,5]\ndel a[3]",number=100000))
print(timeit.timeit("a=[1,2,3,4,5]\na.pop(3)",number=100000))
print(timeit.timeit("a=[1,2,3,4,5]\na.remove(3)",number=100000))
Del vs pop vs remove:
0.019387657986953855
0.02506213402375579
0.033232167130336165
Del()似乎比其他两个快得多,而remove()是最慢的。
同时删除最后一项:
print(timeit.timeit("a=[1,2,3,4,5]\ndel a[-1]",number=100000))
print(timeit.timeit("a=[1,2,3,4,5]\na.pop()",number=100000))
print(timeit.timeit("a=[1,2,3,4,5]\na.remove(5)",number=100000))
Del vs pop vs remove:
0.01974551402963698
0.020333584863692522
0.03434014297090471
Del()和pop()删除最后一项所需的时间相似。
从列表中删除元素的三种不同方法的效果:
Remove删除第一个匹配的值,而不是特定的索引:
>>> a = [0, 2, 3, 2]
>>> a.remove(2)
>>> a
[0, 3, 2]
Del删除特定索引处的项:
>>> a = [9, 8, 7, 6]
>>> del a[1]
>>> a
[9, 7, 6]
pop删除特定索引处的项并返回它。
>>> a = [4, 3, 5]
>>> a.pop(1)
3
>>> a
[4, 5]
它们的错误模式也不同:
>>> a = [4, 5, 6]
>>> a.remove(7)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: list.remove(x): x not in list
>>> del a[7]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range
>>> a.pop(7)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
IndexError: pop index out of range
pop
获取index(如果给定,则获取last),删除该索引处的值,并返回值
删除
获取值,删除第一次出现的内容,并不返回任何内容
删除
获取索引,删除该索引处的值,并不返回任何值