转自：http://safehammad.com/downloads/python-idioms-2014-01-16.pdf
# GOOD
names = ['Safe', 'George', 'Mildred']
for i, name in enumerate(names):
print(i, name) # 0 Safe, 1 George etc.
# NOT SO GOOD
names = ['Safe', 'George', 'Mildred']
count = 0
for name in names:
print(name) # 0 Safe, 1 George etc.
count += 1