通过三种不同的方式逐字逐字地遍历文件的内容（以古腾堡计划的《绿野仙踪》为例）：
from __future__ import with_statement
import time
import re
from cStringIO import StringIO
def word_iter_std(filename):
start = time.time()
with open(filename) as f:
for line in f:
for word in line.split():
yield word
print 'iter_std took %0.6f seconds' % (time.time() - start)
def word_iter_re(filename):
start = time.time()
with open(filename) as f:
txt = f.read()
for word in re.finditer('\w+', txt):
yield word
print 'iter_re took %0.6f seconds' % (time.time() - start)
def word_iter_stringio(filename):
start = time.time()
with open(filename) as f:
io = StringIO(f.read())
for line in io:
for word in line.split():
yield word
print 'iter_io took %0.6f seconds' % (time.time() - start)
woo = '/tmp/woo.txt'
for word in word_iter_std(woo): pass
for word in word_iter_re(woo): pass
for word in word_iter_stringio(woo): pass
导致：
% python /tmp/junk.py
iter_std took 0.016321 seconds
iter_re took 0.028345 seconds
iter_io took 0.016230 seconds
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