directory

  • A preface.
  • 2.Python function definitions
  • Calls to Python functions
  • Pass arguments to Python functions
    • 1. General arguments to Python functions
    • 2. Default parameters of Python functions
    • 3.Python functions have variable arguments
  • The Python function returns the value return
  • 6. Summary of Python functions
  • Seven. Guess you like it

Recommended path for learning Python: Python Learning Directory >> Python Basics

A preface.

Python functions are snippets of code that can be called repeatedly. For example, the type/ID we have seen in previous articles are functions. These functions are built into Python. You don’t have to worry about how it’s done internally.

2.Python function definitions

In Python, to define a function, use the **def** statement, writing out the function name, parentheses, arguments in parentheses, and colon:, and then write the function body in an indent block. The return value of the function is returned by a return statement. If there is no return statement, None is returned by default;

#! Usr /bin/env python # -* -coding :utf-8 _*- "" www.codersrc.com @file :Python function use. py @time :2021/3/29 08:00 @motto: A thousand miles without a small step, a small stream without a river or sea, the wonderful life of program needs to be accumulated with perseverance! """ def functionname( parameters ): "Function_suite return [expression]" def cusom_print(): print("hello world")Copy the code

Calls to Python functions

When code is executed line by line in a py file, if it encounters a function definition, the compiler automatically skips it, executes the code after the function, and calls the function if it wants to.

** Note: functions must be declared before they can be called. Python’s built-in functions such as print/type are already declared and defined in the Python compiler and can be called without worrying about how they are implemented internally. ** Example code is as follows:

#! Usr /bin/env python # -* -coding :utf-8 _*- "" www.codersrc.com @file :Python function use. py @time :2021/3/29 08:00 @motto: A thousand miles without a small step, a small stream without a river or sea, the wonderful life of program needs to be accumulated with perseverance! """ def custom_print(): Print ("hello world") print("hello world") print("hello world") print("hello world")  hello world hello world hello world '''Copy the code

Code analysis: At line 15, the compiler realizes that this is a function declaration, and instead of executing it, it automatically jumps to line 20, and the compiler realizes that line 20 is calling custom_print. It goes directly into the custom_print function and executes line 16/17/18 until the end of the function.

Pass arguments to Python functions

Functions can pass arguments externally, including parameters and arguments:

Print ("cusom_print: x={}". Format (x)) cusom_print(1) //1 is an argument to the function - used to pass arguments when calling the functionCopy the code

1. General arguments to Python functions

As a general rule, functions take several parameters by default, and how many arguments need to be passed when called externally. Example code is as follows:

#! Usr /bin/env python # -* -coding :utf-8 _*- "" www.codersrc.com @file :Python function use. py @time :2021/3/29 08:00 @motto: A thousand miles without a small step, a small stream without a river or sea, the wonderful life of program needs to be accumulated with perseverance! """ def cusom_print1(x): print("cusom_print1 : x={}".format(x)) def cusom_print2(x,y): print("cusom_print2 : x={}".format(x)) print("cusom_print2 : y={}".format(y)) def cusom_print3(x,y,z): print("cusom_print3 : x={}".format(x)) print("cusom_print3 : y={}".format(y)) print("cusom_print3 : Z ={}". Format (z)) cusom_print1(1) Cusom_print2 (1,2) Cusom_print3 (1,2,3) x=1 cusom_print2 : y=2 cusom_print3 : x=1 cusom_print3 : y=2 cusom_print3 : z=3 '''Copy the code

2. Default parameters of Python functions

In Python function arguments, there are default arguments in addition to regular arguments, that is, default arguments have a default value,

  • If the function is called without passing a parameter to the default parameter, the parameter takes the default value.
  • ** If an external call passes a parameter to the default parameter, the value of this parameter should be equal to the parameter passed externally; 支那

Functions with default arguments are also called default functions. Example code is as follows:

#! Usr /bin/env python # -* -coding :utf-8 _*- "" www.codersrc.com @file :Python function use. py @time :2021/3/29 08:00 @motto: A thousand miles without a small step, a small stream without a river or sea, the wonderful life of program needs to be accumulated with perseverance! Print ("cusom_print4: x={}". Format (x)) print("cusom_print4: x={}". Format (x)) print("cusom_print4: x={}". y={}".format(y)) print("cusom_print4 : Z ={}". Format (z)) print("***"*20) cusom_print4(1) Cusom_print4 (1,4) cusom_print4(1,4,3)" x=1 cusom_print4 : y=2 cusom_print4 : z=3 ************************************************************ cusom_print4 : x=1 cusom_print4 : y=4 cusom_print4 : z=3 ************************************************************ cusom_print4 : x=1 cusom_print4 : y=4 cusom_print4 : z=3 ************************************************************ '''Copy the code

Note:

  • 1. Each default parameter has a default value. If no external parameter is passed to the default parameter, the default value is used directly. Otherwise equal to the value of the externally passed argument;

  • 2. Default parameters must be written at the end of function parameters.

    Error writing

    Def cusom_print4(x,y=2,z): print(” cusom_print4: x={} “. Format (x))

3.Python functions have variable arguments

*argc, **kargcs *argc, **kargcs *argc, **kargcs *argc, **kargcs

The Python function returns the value return

The return value of the function is optional, depending on your usage requirements. If the function does not return a value, None is returned by default, andFalseDifferent, it doesn’t represent 0, and it doesn’t represent an empty string, but it represents no value, which is null.

6. Summary of Python functions

  • 1. The function must be declared before the call; otherwise, an error will be reported.
  • 2. Note the default parameter writing method.
  • 3. This function does not use return. By default, it returns None.

Seven. Guess you like it

  1. Python Configuration Environment
  2. Python variable
  3. Python operator.
  4. Python conditions determine if/else
  5. Python while loop
  6. Python break
  7. Python continue
  8. The Python for loop
  9. The Python string
  10. The Python list
  11. The Python tuple tuple
  12. Python dictionary dict
  13. Python conditional derivations
  14. Python list derivations
  15. Python dictionary derivations

Python function declarations and calls

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