The 18th chapter of the Python study manual 4th

" " Date: September 5-September 30 Requirements: 1. Summary of the book contents, finishing in the blog Park notes upload 2. After all the exercises in the course Note: "#" After the addition of the notes (42 pages per day, you can guarantee to read this book at the end of the month) "Key Notes" "chapter Exercises"-Heading 1, level two headings- Heading 2, Notes outline title, exercise title-Bold, 16px"

Key Notes

Summary

A parameter is the way an object is sent to a function as input. Parameters (argument)
I. Pass-through parameters

Here are some brief key points when the function passes a parameter:

• The argument is passed by automatically assigning the object to the local variable name.
• The assignment of the parameter name inside the function does not affect the caller
• Changing the value of a variable object parameter of a function may have an effect on the caller

Two. Specific parameter matching model

Parameters are always passed by assignment in Python. The passed-in object is assigned a variable name on the DEF header.

1. Basic knowledge
   Position: Match from left to right
   keyword parameter : Use the syntax of name = value
   default parameter : defines a parameter value for a parameter that does not have an incoming value, using a syntax such as name = value
   variable Parameters : Collect any number of parameters based on location or keyword, function can use specific parameters, they are starting with a string *, collect any number of extra parameters
   variable parameter unpacking : one-to-many parameters based on location or keyword
   keyword-only parameter : parameter must be passed by name
2. Details
   Inside Python, you use the following steps to match parameters before assigning values:
   ① to assign non-keyword parameters by location;
   ② assigns keyword parameters by matching variable names;
   ③ other additional non-keyword parameters are assigned to the *name tuple;
   ④ Other additional keyword parameters are assigned to the **name dictionary;
   ⑤ with default values assigned to parameters not assigned to the header
   
   

Three. Examples of arbitrary parameters

2. Collect parameters
   The first use: in a function definition, collect mismatched positional parameters in tuples
   

    >>> def  F (*args):  print   >> > F () ()  >>> F (1) ( 1,)  >>> F (1,2,3,4) ( 1, 2, 3, 4) 

    

3. The
4. * * attribute is similar, but it is valid only for the keyword parameter.
   

    >>> def  F (**args):  Span style= "color: #0000ff;" >print   >>> F () {}  >>> F (A=1,b= py   " " {  "  b  :    PY  ,    A  : 1} 

    

6. Mixed usage
   Function head can be mixed with general parameters, * parameters and * * parameters to achieve a more flexible call mode
   

   def F (a,*arg,**args):    print(a,arg,args)    >>> F (1,2,3,x=1  )1 (2, 3) {'x': 1}

Four. Keyword-only parameters

You can use a * character in the argument list to indicate that a function does not accept a parameter list of variable lengths, but still expects all parameters followed by * To be passed as keywords.

This chapter exercises:

1.

Answer: 1 2 5

2.

Answer: 1 2 3

3.

Answer: 1 (2,3)

4.

Answer: 1,{c:3,b:2}

5.

Answer: 1 5 6 4

The 18th chapter of the Python study manual 4th