Looping over a range of numbers
Bad：
for i in [0,1,2,3,4,5]:
print i**2
Good:
for i in range(6):
print i**2
Looping over a collection:
Bad:
colors = [ 'red','green','blue','yellow']
for i in range(len(colors)):
print colors[i]
Good:
for i in colors:
print colors[i]
Looping backwards
Bad:
colors = ['red','green','blue','yellow']
for i in range(len(colors)-1,-1,-1):
print colors(i)
Good:
colors = ['red','green','blue','yellow']
for color in reversed(colors):
print color
Looping over a collection and indicies
Bad:
colors = ['red','green','blue','yellow']
for i in range(len(colors)):
print i, '-->', colors[i]
Good:
colors = ['red','green','blue','yellow']
for i,color in enmerate(colors):
print i, '-->', colors[i]
Looping over two collections
Bad:
names = ['raymond','rachel','mattew']
colors = ['red','green','blue','yellow']
n = min(len(names),len(colors))
for i in range(n):
print names[i],'-->',colors[i]
Good:
names = ['raymond','rachel','mattew']
colors = ['red','green','blue','yellow']
for name,color in zip(names,colors):
print name,'-->',color
Even beeter.(izip 依次处理，zip是全部读入后处理，如果在中间中断的话，izip不需要读入所有内容）
from itertools import izip
names = ['raymond','rachel','mattew']
colors = ['red','green','blue','yellow']
for name,color in izip(names,colors):
print name,'-->',color