python之deque

今天无意间发现python的双向队列模块，之前只知道list，所以就拿来 学习一下。

import collections

help(collections.deque())

Help on deque object:

class deque(builtins.object)
 |  deque([iterable[, maxlen]]) --> deque object
 |  
 |  A list-like sequence optimized for data accesses near its endpoints.
 |  
 |  Methods defined here:
 |  
 |  __add__(self, value, /)
 |      Return self+value.
 |  
 |  __bool__(self, /)
 |      self != 0
 |  
 |  __contains__(self, key, /)
 |      Return key in self.
 |  
 |  __copy__(...)
 |      Return a shallow copy of a deque.
 |  
 |  __delitem__(self, key, /)
 |      Delete self[key].
 |  
 |  __eq__(self, value, /)
 |      Return self==value.
 |  
 |  __ge__(self, value, /)
 |      Return self>=value.
 |  
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |  
 |  __getitem__(self, key, /)
 |      Return self[key].
 |  
 |  __gt__(self, value, /)
 |      Return self>value.
 |  
 |  __iadd__(self, value, /)
 |      Implement self+=value.
 |  
 |  __imul__(self, value, /)
 |      Implement self*=value.
 |  
 |  __init__(self, /, *args, **kwargs)
 |      Initialize self.  See help(type(self)) for accurate signature.
 |  
 |  __iter__(self, /)
 |      Implement iter(self).
 |  
 |  __le__(self, value, /)
 |      Return self<=value.
 |  
 |  __len__(self, /)
 |      Return len(self).
 |  
 |  __lt__(self, value, /)
 |      Return self integer -- return number of occurrences of value
 |  
 |  extend(...)
 |      Extend the right side of the deque with elements from the iterable
 |  
 |  extendleft(...)
 |      Extend the left side of the deque with elements from the iterable
 |  
 |  index(...)
 |      D.index(value, [start, [stop]]) -> integer -- return first index of value.
 |      Raises ValueError if the value is not present.
 |  
 |  insert(...)
 |      D.insert(index, object) -- insert object before index
 |  
 |  pop(...)
 |      Remove and return the rightmost element.
 |  
 |  popleft(...)
 |      Remove and return the leftmost element.
 |  
 |  remove(...)
 |      D.remove(value) -- remove first occurrence of value.
 |  
 |  reverse(...)
 |      D.reverse() -- reverse *IN PLACE*
 |  
 |  rotate(...)
 |      Rotate the deque n steps to the right (default n=1).  If n is negative, rotates left.
 |  
 |  ----------------------------------------------------------------------
 |  Static methods defined here:
 |  
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.
 |  
 |  ----------------------------------------------------------------------
 |  Data descriptors defined here:
 |  
 |  maxlen
 |      maximum size of a deque or None if unbounded
 |  
 |  ----------------------------------------------------------------------
 |  Data and other attributes defined here:
 |  
 |  __hash__ = None

# 创建双向队列
dq = collections.deque()

# 从右端添加元素
for i in range(2,5):
    dq.append(i)
dq

deque([2, 3, 4])

# 从左端添加元素
dq.appendleft(-2)
dq

deque([-2, 2, 3, 4])

# 从右端扩展一个列表元素
list1 = [6,6,6]
dq.extend(list1)
dq

deque([-2, 2, 3, 4, 6, 6, 6])

# 从左端扩展一个列表元素
dq.extendleft(list1)
dq

deque([6, 6, 6, -2, 2, 3, 4, 6, 6, 6])

# 在指定位置插入元素
dq.insert(2,'b')
dq

deque([6, 6, 'b', 6, -2, 2, 3, 4, 6, 6, 6])

# 从队列右端删除元素
dq.pop()
dq

deque([6, 6, 'b', 6, -2, 2, 3, 4, 6, 6])

# 从队列左端删除元素
dq.popleft()
dq

deque([6, 'b', 6, -2, 2, 3, 4, 6, 6])

# 计算队列中指定元素的个数
dq.count(6)

4

# 复制队列
dq1 = dq.copy()
dq1

deque([6, 'b', 6, -2, 2, 3, 4, 6, 6])

dq1.clear()
dq1

deque([])

dq

deque([6, 'b', 6, -2, 2, 3, 4, 6, 6])

# 返回队列元素所在位置
dq.index("b")

1

更多学习可以参见help（collections.deque()）。