1 、背景：
想知道5种遍历方法，并且知道从性能角度考虑，使用哪种。
2、结论：
使用这种方式：
for key,val in AutoDict.iteritems():
temp = "%s:%s" % (key,val)
不用这种方式：
for (key,val) in AutoDict.items():
temp = "%s:%s" % (key,val)
实验：
import time
def testDict():
count = 1000000
AutoDict = {}
for i in xrange(count):
AutoDict[i] = i
startTime = time.time()
for d in AutoDict:
temp = "%s:%s" % (d,AutoDict[d])
#method 1
print 'span time 1 :%s' % str(time.time()-startTime)
startTime = time.time()
for (key,val) in AutoDict.items():
temp = "%s:%s" % (key,val)
#method 2
print 'span time 2 :%s' % str(time.time()-startTime)
startTime = time.time()
for key,val in AutoDict.iteritems():
temp = "%s:%s" % (key,val)
#method 3
print 'span time 3 :%s' %str(time.time()-startTime)
startTime = time.time()
for key in AutoDict.iterkeys():
temp = "%s:%s" %(key,AutoDict[key])
#method 4
print 'span time 4 :%s' %str(time.time()-startTime)
startTime = time.time()
for key,val in zip(AutoDict.iterkeys(),AutoDict.itervalues()):
temp = "%s:%s" %(key,val)
#method 5
print 'span time 5 :%s' %str(time.time()-startTime) testDict()
多次实验的平均值：
span time 1 :0.206
span time 2 :0.508
span time 3 :0.195
span time 4 :0.205
span time 5 :0.307