collections.deque

python数据类型

collections.deque类(双向队列)是一个线程安全、可以快速从两端添加或者删除元素的数据类型。

类

class collections.deque([iterable[, maxlen]])

• maxlen： 代表这个队列可以容纳的元素的数量,而且一旦设定,这个属性就不能修改了。如果没有给定参数，则容量为无限大。

方法

append()

Add x to the right side of the deque.

append(x)

appendleft()

Add x to the left side of the deque.

appendleft(x)

pop()

Remove and return an element from the right side of the deque. If no elements are present, raises an IndexError.

popleft()

Remove and return an element from the left side of the deque. If no elements are present, raises an IndexError.

extend()

Extend the right side of the deque by appending elements from the iterable argument.

extend(iterable)

extendleft()

Extend the left side of the deque by appending elements from iterable. Note, the series of left appends results in reversing the order of elements in the iterable argument.

extendleft(iterable)

insert(i, x)

Insert x into the deque at position i.

If the insertion would cause a bounded deque to grow beyond maxlen, an IndexError is raised.

clear()

Remove all elements from the deque leaving it with length 0.

copy()

Create a shallow copy of the deque.

count(x)

Count the number of deque elements equal to x.

count(x)

index(x[, start[, stop]])

Return the position of x in the deque (at or after index start and before index stop). Returns the first match or raises ValueError if not found.

remove()

Remove the first occurrence of value. If not found, raises a ValueError.

remove(value)

reverse()

Reverse the elements of the deque in-place and then return None.

rotate()

Rotate the deque n steps to the right. If n is negative, rotate to the left.
- n > 0 , 队列的最右边的 n 个元素会被移动到队列的左边
- n < 0, 最左边的 n 个元素会被移动到右边

When the deque is not empty, rotating one step to the right is equivalent to d.appendleft(d.pop()), and rotating one step to the left is equivalent to d.append(d.popleft()).

只读属性

maxlen

Maximum size of a deque or None if unbounded.

deque中实现的方法

实现的一般方法

实现的特殊方法