Python: Functions

* parameter vs. argument
	parameter: names given in the function definition
	argument: values supply in the function call
	
* pass by value?

* global statement
	tell python the varible is actually defined in an OUTERMOST block
	
* nonlocal statement
	
* scope 作用域
	与javascript类似，python没有block级作用域，但是有函数级作用域
def scope():
    i='i'
    if True:
        j='j'
        if True:
            k = 'k'
        print(k) # k is available here
    print(j) # j is available here

scope()
print(i) # i is not available here

* default argument values
	the arguments which have the default values should be place at the end of the parameter list

* keyword arguments
	when calling a function, you can specify the name of the argument
	
* ? varArgs parameters

* documentation string
	a string on the first logical ine of a function.
	use funcName.__doc__ to retrieve