(一)函数的定义

1 def hello():
2     print("Hoddy!")
3     print("Hoddy!!")
4 hello()
5 hello()

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输出结果：

Hoddy!
Hoddy!！
Hoddy!
Hoddy!！

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(二)带有参数的函数

1 def hello(name):
2     print("Hello " + name)
3 hello('sara')

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输出结果：

Hello sara

(三)返回值和返回语句

返回语句包含：return关键字和返回值或者表达式

 1 mport random
 2 def getAnswer(answerNumber):
 3     if answerNumber ==1:
 4         return 'It is certain'
 5     elif answerNumber == 2:
 6         return 'It is decidedly so'
 7     elif answerNumber == 3:
 8         return 'Yes'
 9 r = random.randint(1,4)
10 fortune = getAnswer(r)
11 print(fortune)

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print(getAnswer(random.randint(1, 9)))

注意：表达式由值和表达式组成，函数的调用可以使用表达式，因为它计算结果为它的返回值

(四)空值(The None value)

>>>spam = print('Hello!')

Hello

>>>None == spam

True

(五)关键字参数和print()

print('Hello')

print('world')

Hello

world

print('Hello',end='')

print('world')

输出：Helloworld

>>>print('cats','dogs','mice')

cats dogs mice

>>>print('cats','dogs','mice',sep=',')

cats,dogs,mice

 (六)全局变量和局部变量

 1)局部变量不能用于全局范围

1 def spam():
2     eggs = 3313
3 spam()
4 print(eggs)

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2)局部作用域不能使用其他局部作用域中的变量

1 def spam():
2     eggs = 3313
3     bacon()
4     print(eggs)
5 def bacon():
6     ham =101
7     eggs =0
8 spam()

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3)局部作用域可以读取全局变量

1 def spam():
2     print(eggs)
3 eggs=43
4 spam()
5 print(eggs)

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4)全局和局部作用域中可以使用相同的变量名称

(七)全局声明

 1 def spam():
 2     global  eggs
 3     eggs = 'spam'
 4 def bacon():
 5     eggs = 'bacon'
 6 
 7 def ham():
 8     print(eggs)
 9 
10 eggs=43
11 spam()
12 print(eggs)

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输出结果：

spam