Python Special Syntax

#!/usr/bin/python
# Filename: for.py

for i in range(1, 5):
    print i
else:
    print ‘The for loop is over‘

for循环在这个范围内递归——for i in range(1,5)等价于for i in [1, 2, 3, 4]

如果包含else，它总是在for循环结束后执行一次，除非遇到break语句。

关于局部变量：这个绝对让人震惊！

#!/usr/bin/python
# Filename: func_local.py

def func(x):
    print ‘x is‘, x
    x = 2
    print ‘Changed local x to‘, x

x = 50
func(x)
print ‘x is still‘, x

结果是：

x is 50
Changed local x to 2
x is still 50

当然可以使用global关键字：

#!/usr/bin/python
# Filename: func_global.py

def func():
    global x

    print ‘x is‘, x
    x = 2
    print ‘Changed local x to‘, x

x = 50
func()
print ‘Value of x is‘, x

输出结果为：

x is 50
Changed global x to 2
Value of x is 2

转自：http://woodpecker.org.cn/abyteofpython_cn/chinese/ch07s04.html

Python Special Syntax