Python function parameter type

parameters of the function

To define a function (parameter):

Generic parameters, default parameters, variable parameters (variable position parameters, variable keyword parameters), keyword-only parameters

Call Function (argument):

Position parameter, key word parameter, parameter structure (location parameter deconstruction, keyword parameter deconstruction)

general parameter X,y:

def add (x,y)

return x + y

default parameter x=1:

Def Inc (Base,x =1):

Return base +x

Inc (3)

4

Inc (3,2)

5

A parameter can have a default value, but when a parameter has a default value, the default value is used if the parameter is not passed when invoked

A default value parameter must be followed without a default value parameter, or an error will be syntaxerror

DEF Inc (X=0,y):

Return X+y

File "<ipython-input-19-d6c7b4f89658>", Line 1
    def Inc (x= 0,y):
           ^
syntaxerror:non-default argument Follows default argument

variable position parameters:

When defining a parameter, precede with a *, which means that the parameter is variable and can accept any number of parameters that constitute a tuple and can only be passed by positional parameters

Variable keyword parameters:

When defining parameters, add * * above to indicate that this parameter is variable and can accept any number of arguments that form a dictionary and can only be passed by keyword parameters

Mixed use of parameters:

#位置参数可以和关键字参数一起使用
#当位置可变参数和关键字可变参数一起使用时候, the variable position parameters must be in the front

DEF fn (*args,**kwargs):

    Print (args)

    Print (Kwargs)

FN (1,2,3,x=4,y=5)

(1,2,3)  

(1, 2, 3)
{' Y ': 5, ' X ': 4}

#普通参数可以和可变参数一起使用, but must match when passing the argument

DEF fn (X,y,*args,**kwargs):

    Print (x)

    Print (y)

    Print (args)

    Print (Kwargs)

FN (1,2,3,4,5,a=6,b=7)

1

1
2
(3, 4, 5)
{' A ': 6, ' B ': 7}

#关键字可变参数不允许在普通参数之前

DEF fn (**kwargs,x):

Print (x)

#上面的方式定义会出错

#默认参数可以在可变位置参数之前

DEF fn (X=5,*args):

Print (x)

Pprint (args)

#位置可变参数可以在普通参数之前, but the normal parameter after the position variable parameter becomes a keyword-only parameter

keyword-only Parameters:

Python3 Characteristics

The parameter after #在 * Number can only be passed by keyword parameter called keyword-only parameter

The parameter after the variable position parameter is also the keyword-only parameter

DEF fn (*,x):

Print (x)

FN (1,x=3) #此时x can only be passed by keyword parameters, and if normal parameter passing is installed, it will be eaten by * and variable position parameters

FN (x=3)

DEF fn (*args,x):

Print (args)

Print (x)

#keyword-only parameter can have a default value

The keyword-only parameter can appear with the default parameter, regardless of whether it has a default value, regardless of whether the default parameter is Keyword-only

parameter deconstruction:

An iterative object can be used to form positional parameters

Parameter deconstruction takes place in function calls, and variable parameters occur when the function is defined

Two forms of deconstruction:

An asterisk *, the deconstruction of an object: An iterative object, the result of the deconstruction, the positional parameter

Two asterisks * *, deconstruction objects: dictionaries, deconstruction results, keyword parameters

Keyword argument deconstruction, key must be str type

def add (a,b):
Return a+b
data = [4,3]
Print (Add (*data)) #位置参数解构
Data1 = {' A ': 3, ' B ': 4}
Print (Add (**data1)) #关键字参数解构