Review of some Python's key value

# yield

def foo():

yield 1

yield 2

yield 9999

a = foo()

for i in a:

print i

>>> 1

2

9999

实例：

readline to readlines

def xreadlines():

seek=0

while 1:

with open('file.txt','r+') as f:

data = f.readline()

if data:

seek = f.tell()

yield data

else:

return

a = xreadlines()

type(a)

for i in a:

print i

# 三元运算

在C中

if x>y ?tmp= a:b

在Python中

tmp = a if x>y else b

# with ... as...

#lambda x,y:x+y