def <name>(arg1,arg2,arg3，……,argN):

　　<statements>

if test:
  def fun():
    ...
else:
  def func():
    ...
...
func()

othername=func()
othername()

>>> import math
>>> x=1
>>> y=math.sqrt
>>> callable(x)
False
>>> callable(y)
True

>>> def hello(name):
 　　 return 'Hello, '+name+'!'
>>> print hello('world')
Hello, world!
>>> print hello('Gumby')
Hello, Gumby!

>>> def fibs(num):
  　　 result=[0,1]
  　　for i in range(num-2):
    　　 result.append(result[-2]+result[-1])
  　　 return result
>>> fibs(10)
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
>>> fibs(15)
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377]

>>> def try_to_change(n):
 　　 n='Mr.Gumby'
>>> name='Mrs.Entity'
>>> try_to_change(name)
>>> name
'Mrs.Entity'

>>> name='Mrs.Entity'
>>> try_to_change(name)
>>> name
'Mrs.Entity'
>>> def change(n):
  　　 n[0]='Mr.Gumby'

>>> name=['Mrs.Entity','Mrs.Thing']
>>> change(name)
>>> name
['Mr.Gumby', 'Mrs.Thing']

>>> name=['Mrs.Entity','Mrs.Thing']
>>> n=name #再来一次，模拟传参行为
>>> n[0]='Mr.Gumby' #改变列表
>>> name
['Mr.Gumby', 'Mrs.Thing']

>>> names=['Mrs.Entity','Mrs.Thing']
>>> n=names[:]
>>> n is names
False
>>> n==names
True

>>> n[0]='Mr.Gumby'
>>> n
['Mr.Gumby', 'Mrs.Thing']
>>> names
['Mrs.Entity', 'Mrs.Thing']
>>> change(names[:])
>>> names
['Mrs.Entity', 'Mrs.Thing']

>>> def hello(greeting, name):
    print '%s,%s!'%(greeting, name)
>>> hello(greeting='hello',name='world!')
hello,world!!

>>> def hello_1(greeting='hello',name='world!'):
  　　print '%s,%s!'%(greeting,name)

>>> hello_1()
hello,world!!
>>> hello_1('Greetings')
Greetings,world!!
>>> hello_1('Greeting','universe')
Greeting,universe!

>>> hello_1(name='Gumby')
hello,Gumby!

>>> def print_params(*params):
  　　 print params

>>> print_params('Testing')
('Testing',)
>>> print_params(1,2,3)
(1, 2, 3)

>>> def print_params_2(title,*params):
  　　 print title
  　　 print params

>>> print_params_2('params:',1,2,3)
params:
(1, 2, 3)
>>> print_params_2('Nothing:')
Nothing:
()

>>> print_params_2('Hmm...',something=42)
Traceback (most recent call last):
 File "<pyshell#112>", line 1, in <module>
  print_params_2('Hmm...',something=42)
TypeError: print_params_2() got an unexpected keyword argument 'something'

>>> def print_params(**params):
  　　 print params

>>> print_params(x=1,y=2,z=3)
{'y': 2, 'x': 1, 'z': 3}
>>> def parames(x,y,z=3,*pospar,**keypar):
  　　 print x,y,z
  　　 print pospar
  　　 print keypar

>>> parames(1,2,3,5,6,7,foo=1,bar=2)
1 2 3
(5, 6, 7)
{'foo': 1, 'bar': 2}
>>> parames(1,2)
1 2 3
()
{}
>>> def print_params_3(**params):
  　　 print params

>>> print_params_3(x=1,y=2,z=3)
{'y': 2, 'x': 1, 'z': 3}
>>> #返回的是字典而不是元组
>>> #组合‘#'与'##'
>>> def print_params_4(x,y,z=3,*pospar,**keypar):
  　　 print x,y,z
  　　 print pospar
  　　 print keypar

>>> print_params_4(1,2,3,5,6,7,foo=1,bar=2)
1 2 3
(5, 6, 7)
{'foo': 1, 'bar': 2}
>>> print_params_4(1,2)
1 2 3
()
{}