Basic knowledge of Python (v)

One, variable 1, reference ID ()

A function that participates in a return value is a reference to the saved data.

2, mutable and immutable types (the reference address of a variable changes only after the assignment statement)

• Immutable type data in memory is not allowed to be modified
  1. Number Type Int,bool,float,complex,long (2,x)
  2. String str
  3. Tuple tuples
• Data in variable-type memory can be modified
  1. Lists List
  2. Dictionary Dict
     • The dictionary key can only use immutable type data
  3. Hashing (hash)
     • A function called hash (0) is built into Python.
       • Accept an immutable data as a parameter returns a result as an integer
       • A hash is an algorithm that extracts the signature (fingerprint) of the data.
         • Same content gets the same result
         • Different content gets different results
       • When setting a dictionary key-value pair in Python, the key is first hashed to determine how to save the dictionary data in memory to facilitate subsequent additions and deletions.
         • Key-value pairs must be of immutable type data
         • Value can be any type of data

3. Local variables and global variables

• A reference to a global variable is not allowed to be directly modified inside the function-that is, the value of the global variable is modified with an assignment statement
• So how do you modify the value of a global variable inside a function?
  • Declaring with the global command
  • The Global keyword tells you that the variable following the interpreter is a globally variable
  • A local variable is not created when the assignment statement is re-used

• Global variable can be added G_/gl_ (shortcut key SHIFT+F6 change name)

Second, function 1, tuples can return multiple values

2. Exchange two variables

# The right side of the equals sign is a tuple, just omitting the parentheses , a, B, a

3. Using methods inside a function to modify variable parameters affects external arguments4. The list variable encounters the Extend method which is essentially a list variable

5. Default parameter (a default value specified for a parameter)

• Example: (typically using the most common values as default values for default parameters)
• Default parameters with defaults are placed at the end of the parameter list!!!
• To specify the parameter name when multiple default parameters have defaults
  

6. Multivalued parameters (the number of arguments to be processed by the function is indeterminate)

• Add a * to receive tuples before the parameter name
• Add a * * before the parameter name to receive the dictionary

The general habit of the following two names:

• *args the meaning of the abbreviated variable that holds the tuple parameter arguements
• **kwargs the meaning of the abbreviation key value of the keyword for storing the tuple parameter to the parameter

Split Package

Example:

Basic knowledge of Python (v)