When Python defines a function, the delivery of different parameter types

The bottom of Python is implemented through the C language, so parameters are called by address (as in C, values are one-way, pointers can be passed in two directions), such as:

#-*-Coding:utf-8-*-
def f1 (x, y):
    z=x+y
 y=x
return Z

a 1 b=2c=F1 (A, B) print C, a, b

The result is

3 1 2

From here we can see that the B value has not changed, that is to say, the value is one-way pass.

When defining a function, a parameter can be a numeric value, a list (when tuples are processed), a dictionary, and so on, whose parameters are defined as follows:

Def f (A, *pargs, * *Kargs):     print (A, pargs, Kargs)

In fact, this is a very important feature of Python, that is, arbitrary arguments. When you need a function to support any number of arguments, you will use it. In the example above, Python will treat the matching parameters as a tuple (Ganso). You can call function f like this,

F (13'abc', ('lls'POW ' ' A ')

Print out the results as follows:

(1, (3'abc', ('lls'POW  ')), {'param1'A'})

Python will assign 1 to the parameter A, 3, ' abc ', (' lls ', ' pow ') to pargs, and you can see that Pargs is assigned with a tuple (3, ' abc ', (' lls ', ' pow ')).
Similarly, a kargs that appears in front of the two asterisk will be matched by a dictionary, which means that all incoming parameters like param = X are transferred to the Dict assignment to Kargs.

It is important to note that when defining a function **kargs This type of argument must be placed at the end (if any), and *pargs This type of argument must precede the type parameter **kargs the other type parameter.
For example, the following definitions are illegal.

Def f (A, *b, c=6, * *D)    :**b, *c):    passdef F (*a, * *B, c    ):*c, * *D, E) :    Pass

And the following definitions are all legal.

Def f (A, * *b)    :*b):    passdef F (*a, * *b):    passsdef F (*a):    Passdef F (A, b=1, *c, * *D):    pass

To give a practical example, write a function, enter any number of numbers as parameters, find the largest one, you can use the *pargs we mentioned, the code is as follows:

1def MAX (*pargs):2Maxnum = pargs[0]3      forIinchpargs[1:]:4         ifi >Maxnum:5Maxnum =I6     returnMaxnum7 8Print Max (5,3,1, +, Wu, at,1,2, +)

Results Print 54.

Reference post: http://blog.chinaunix.net/uid-29466937-id-5752171.html

When Python defines a function, the delivery of different parameter types