python学习笔记之函数(方法)

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：

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

在函数内改变全局变量的值(global)

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

结果：

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

默认参数

def say(message, times = 1):
    print message * times

say('Hello')
say('World', 5)

结果：

Hello
WorldWorldWorldWorldWorld

关键参数

def func(a, b=5, c=10):
    print 'a is', a, 'and b is', b, 'and c is', c

func(3, 7)
func(25, c=24)
func(c=50, a=100)

结果：

a is 3 and b is 7 and c is 10
a is 25 and b is 5 and c is 24
a is 100 and b is 5 and c is 50

函数的return

def maximum(x, y):
    if x > y:
        return x
    else:
        return y

print maximum(2, 3)

结果：3

空语句块pass

def someFunction():
    pass

DocStrings

读取函数的doc注释信息，DocStrings也适用于模块和类

文档字符串的惯例是一个多行字符串，它的首行以大写字母开始，句号结尾。第二行是空行，从第三行开始是详细的描述。

def printMax(x, y):
    '''Descript:
        this is printMax function descript
    end.'''
    x = int(x) # convert to integers, if possible
    y = int(y)

    if x > y:
        print x, 'is maximum'
    else:
        print y, 'is maximum'

printMax(3, 5)
print printMax.__doc__
print '---'
help(printMax)

结果

5 is maximum
Descript:
        this is printMax function descript
    end.
---
Help on function printMax in module __main__:

printMax(x, y)
    Descript:
        this is printMax function descript
    end.