Python中字典遍歷的方法以及效能

python中字典的遍歷方式有多種，』items』, 『iteritems』, 『keys』,』iterkeys』, 『itervalues』等方法都可以遍歷字典中的鍵或值，下面通過各種方法來看一下遍歷字典使用不同方法時的效能。**如下：

#!/usr/bin/env python

from time import clock
lst = [(x, x) for x in xrange(10000000)]
dic = dict(lst)
defmethod1
():    start_time = clock()
for i in dic :
t = i + dic[i]
end_time = clock()
print
"method 1 costs time is : " , str(end_time - start_time)
defmethod2
():    start_time = clock()
for k, v in dic.items() :
t = k + v
end_time = clock()
print
"method 2 costs time is : " , str(end_time - start_time)
defmethod3
():    start_time = clock()
for k, v in dic.iteritems() :
t = k + v
end_time = clock()
print
"method 3 costs time is : " , str(end_time - start_time)
defmethod4
():    start_time = clock()
for k in dic.keys():
t = k + dic[k]
end_time = clock()
print
"method 4 costs time is : " , str(end_time - start_time)  
defmethod5
():    start_time = clock()
for k in dic.iterkeys():
t = k + dic[k]
end_time = clock()
print
"method 5 costs time is : " , str(end_time - start_time)  
defmethod6
():    start_time = clock()
for k, v in zip(dic.iterkeys(), dic.itervalues()) :
t = k + v
end_time = clock()
print
"method 6 costs time is : " , str(end_time - start_time)
if __name__ == '__main__' : method1(), method2(), method3(),method4(),method5(),method6()

method 1 costs

time
is :
0.655
method 2 costs
time
is :
5.226
method 3 costs
time
is :
0.64
method 4 costs
time
is :
0.687
method 5 costs
time
is :
0.624
method 6 costs
time
is :
2.028

method 1 costs

time
is :
0.639
method 2 costs
time
is :
5.335
method 3 costs
time
is :
0.64
method 4 costs
time
is :
0.687
method 5 costs
time
is :
0.639
method 6 costs
time
is :
2.027

method 1 costs

time
is :
0.64
method 2 costs
time
is :
5.336
method 3 costs
time
is :
0.64
method 4 costs
time
is :
0.702
method 5 costs
time
is :
0.655
method 6 costs
time
is :
2.027

method 1 costs

time
is :
0.655
method 2 costs
time
is :
5.475
method 3 costs
time
is :
0.671
method 4 costs
time
is :
0.687
method 5 costs
time
is :
0.655
method 6 costs
time
is :
2.027

method 1 costs

time
is :
0.64
method 2 costs
time
is :
5.335
method 3 costs
time
is :
0.64
method 4 costs
time
is :
0.702
method 5 costs
time
is :
0.624
method 6 costs
time
is :
2.028

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