python Deque中的计数元素

Question

I've attempted to count 1 values within my deque ( ie deque.count(1) ) but get the following error:

'deque' object has no attribute 'count'  

I assume that I am working with a Python version that's before 2.7 when the deque.count() function was first introduced.

Besides using a for loop , what would be the most efficient/fastest way of counting how many 1's there are in my deque ?

Answer 1

“无循环”的要求很奇怪，但是如果您好奇的话...

len(filter(lambda x: x == 1, d))

Answer 2

I know you asked for no for loops, but I don't think there's any other way:

def count(dq, item):
    return sum(elem == item for elem in dq)

For example:

>>> from collections import deque
>>> d = deque([1, 2, 3, 1])
>>> count(d, 1)
2