python-每次处理一个字符的方式及效率

在python中用过的遍历的方法大概有3种：

第一种是直接用for循环

 

for i in str:
    fuc(i)

第二种是用列表中的for循环

[fuc(i) for i in str]

第三种是用map函数

map(fuc, thestr)

而他们的效率又如何呢？

import time
str_file = open('test.txt')
thestr = str_file.read()
start_time1 = time.time()
f_str = 0
for s in thestr:
    f_str = ord(s)
end_time1 = time.time()
print end_time1-start_time1

start_time2 = time.time()
f_str = 0
f_str = [ord(s) for s in thestr]
end_time2 = time.time()
print end_time2-start_time2

start_time3 = time.time()
f_str = 0
f_str = map(ord, thestr)
end_time3 = time.time()
print end_time3-start_time3

2.64099979401
2.93800020218
0.90700006485