来源:https://segmentfault.com/q/1010000002581747
方法一:直接遍历 速度快
for key in _dict:
pass
方法二:iterkeys() 速度快
for _ in testDict.iterkeys():
pass
方法三:keys() 速度慢 因为keys()须要形成一个列表,构建一个列表对于一个大的dict开销是很大的。
for _ in testDict.keys():
pass
时间对比:
import timeitDICT_SIZE = 100*10000testDict = dict()
for i in range(DICT_SIZE):
testDict[i] = i # 构建大小为100W的字典assert len(testDict) == DICT_SIZEdef test1():
for _ in testDict.keys():
passdef test2():
for _ in testDict:
passdef test3():
for _ in testDict.iterkeys():
pass
# 分别测试2K次
print timeit.timeit("test1()", setup="from __main__ import test1", number=2000)
print timeit.timeit("test2()", setup="from __main__ import test2", number=2000)
print timeit.timeit("test3()", setup="from __main__ import test3", number=2000)
输出
54.1994677764
30.2660675759
31.3075812315
是windows + python 2.7的结果