Python作为一门脚本语言,有着很多便捷易用的优秀特点,但他也有一个很大的缺陷,就是性能太差,这也是作为脚本语言不可避免的问题,这里我们来学习一些方法,提高Python的性能:
为了大家测试方便,这里同时给了代码的图片版和文字版。
Python虽然不能利用多线程实现多核任务,但可以通过多进程实现多核任务。多个Python进程有各自独立的GIL锁,互不影响。
multiprocessing.Queue
用于多进程:
先来看官方文档:
from multiprocessing import Pool deff(x): returnx*x if__name__=='__main__': withPool(5)asp: print(p.map(f,[1,2,3])) 输出: [1,4,9]
multiprocessing supports two types of communication channel between processes:
multiprocessing支持两种类型的进程间通信方式queues和pips。
Queues
The Queue class is a near clone of queue.Queue. For example:
Queue是queue.Queue的近似克隆。
from multiprocessing import Process,Queue deff(q): q.put([42,None,'hello']) if__name__=='__main__': q=Queue() p=Process(target=f,args=(q,)) p.start() print(q.get())# prints "[42, None, 'hello']" p.join() Queues are thread and process safe.
Queues是进程和线程安全的,也就是说,同一时间,只能由一个进程或者线程操作Queues。
queue
先来看官方文档:
def worker(): whileTrue: item=q.get() ifitem is None: break do_work(item) q.task_done() q=queue.Queue() threads=[] foriinrange(num_worker_threads): t=threading.Thread(target=worker) t.start() threads.append(t) foritem insource(): q.put(item) # block until all tasks are done q.join() # stop workers foriinrange(num_worker_threads): q.put(None) fortinthreads: t.join()
collections.deque
先来看官方文档:
有人对比过以上三者的性能,deque作为一种双向队列性能完胜其他两者。
>>>from collections import deque >>>d=deque('ghi')# make a new deque with three items >>>forelem ind:# iterate over the deque's elements ...print(elem.upper()) G H I >>>d.append('j')# add a new entry to the right side >>>d.appendleft('f')# add a new entry to the left side >>>d# show the representation of the deque deque(['f','g','h','i','j']) >>>d.pop()# return and remove the rightmost item 'j' >>>d.popleft()# return and remove the leftmost item 'f' >>>list(d)# list the contents of the deque ['g','h','i'] >>>d[0]# peek at leftmost item 'g' >>>d[-1]# peek at rightmost item 'i' >>>list(reversed(d))# list the contents of a deque in reverse ['i','h','g'] >>>'h'ind# search the deque True >>>d.extend('jkl')# add multiple elements at once >>>d deque(['g','h','i','j','k','l']) >>>d.rotate(1)# right rotation >>>d deque(['l','g','h','i','j','k']) >>>d.rotate(-1)# left rotation >>>d deque(['g','h','i','j','k','l']) >>>deque(reversed(d))# make a new deque in reverse order deque(['l','k','j','i','h','g']) >>>d.clear()# empty the deque >>>d.pop()# cannot pop from an empty deque Traceback(most recent call last): File"<pyshell#6>",line1,in-toplevel- d.pop() IndexError:pop froman empty deque >>>d.extendleft('abc')# extendleft() reverses the input order >>>d deque(['c','b','a'])