variable in the function

when assign a name A in a function, it will create a local variable a

In the function, we can read the value of global variable A

However, if you want to modify global variable A, you must using following methods:

global:

use global to modify global variable

ex:

x=1

def  test():

      global  x

      x=3

access attribute in other module:

using import

ex:

import  test

test.var = 2

nested function:

ex:

def test:

    x=3

    def  test2:

        print x

test2 can access x defined in test 

keyword parameter

ex:

def  test(a, b):

        print  a, b

test( a=3, b=2)

default parameter:

ex:

def  test(a, b=3):

       printf  a, b

test( 2)

arbitrary argument:

ex:

def  test(*args):

       print args

test( 1,2,3)

** is for keyboard argument

ex:

def  test(**args):

      print  args

test(a=1,b=2)

use * in caller:

unpack a collection of arguments

ex:

a= (1,2,3,4)

test( *a)

use ** in caller:

unpack a dictionary of key/value pairs