我會認爲這種差異是因爲你在e
中構建列表和數組,而你只在d
中構造列表。試想一下:
import numpy as np
def d():
a = [1,2,3,4,5]
b = [10,20,30,40,50]
c = [i*j for i,j in zip(a,b)]
return c
def e():
a = np.array([1,2,3,4,5])
b = np.array([10,20,30,40,50])
c = a*b
return c
#Warning: Functions with mutable default arguments are below.
# This code is only for testing and would be bad practice in production!
def f(a=[1,2,3,4,5],b=[10,20,30,40,50]):
c = [i*j for i,j in zip(a,b)]
return c
def g(a=np.array([1,2,3,4,5]),b=np.array([10,20,30,40,50])):
c = a*b
return c
import timeit
print timeit.timeit('d()','from __main__ import d')
print timeit.timeit('e()','from __main__ import e')
print timeit.timeit('f()','from __main__ import f')
print timeit.timeit('g()','from __main__ import g')
這裏的功能f
和g
避免重新創建每次繞列表/陣列,我們得到了非常相似的性能:
1.53083586693
15.8963699341
1.33564996719
1.69556999207
注意list-COMP + zip
仍然獲勝。但是,如果我們的陣列足夠大,numpy的勝手了:
t1 = [1,2,3,4,5] * 100
t2 = [10,20,30,40,50] * 100
t3 = np.array(t1)
t4 = np.array(t2)
print timeit.timeit('f(t1,t2)','from __main__ import f,t1,t2',number=10000)
print timeit.timeit('g(t3,t4)','from __main__ import g,t3,t4',number=10000)
我的結果是:
0.602419137955
0.0263929367065
也許相關:http://stackoverflow.com/questions/5956783/numpy-float-10x-slower-than-builtin-in-arithmetic-operations –
你應該使用更大的數組進行這種測試 –