> def hello() :
　　print("Hello World!")
> hello()
Hello World!
>

def area(width, height):
　　return width * height
def print_welcome(name):
　　print("Welcome", name)
print_welcome("Fred")
w = 4
h = 5
print("width =", w, " height =", h, " area =", area(w, h))

#!/usr/bin/env python3
a = 4 # 全局变量
def print_func1():
　　a = 17 # 局部变量
　　print("in print_func a = ", a)
def print_func2():
　　print("in print_func a = ", a)
print_func1()
print_func2()
print("a = ", a)

def parrot(voltage, state='a stiff', action='voom',
type='Norwegian Blue'):
　　print("-- This parrot wouldn't", action, end=' ')
　　print("if you put", voltage, "volts through it.")
　　print("-- Lovely plumage, the", type)
　　print("-- It's", state, "!")

parrot(1000) # 1 positional argument
parrot(voltage=1000) # 1 keyword argument
parrot(voltage=1000000, action='VOOOOOM') # 2 keyword arguments
parrot(action='VOOOOOM', voltage=1000000) # 2 keyword arguments
parrot('a million', 'bereft of life', 'jump') # 3 positional arguments
parrot('a thousand', state='pushing up the daisies') # 1 positional, 1 keyword

parrot() # required argument missing
parrot(voltage=5.0, 'dead') # non-keyword argument after a keyword argument
parrot(110, voltage=220) # duplicate value for the same argument
parrot(actor='John Cleese') # unknown keyword argument

def return_sum(x,y):
　　c = x + y
　　return c
res = return_sum(4,5)
print(res)

def empty_return(x,y):
　　c = x + y
　　return res = empty_return(4,5)
print(res)

def arithmetic_mean(*args):
　　sum = 0
　　for x in args:
　　　　sum += x
　　return sum
print(arithmetic_mean(45,32,89,78))
print(arithmetic_mean(8989.8,78787.78,3453,78778.73))
print(arithmetic_mean(45,32))
print(arithmetic_mean(45))
print(arithmetic_mean())