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08 Python function classes and objects
1. Function
1. Definition of function
def 函数名 (参数列表）:
函数体
return 返回值列表
The parameter list can be 0, 1 or more, and multiple parameters are separated by commas
2. Function call
函数名(实参)
3.tips
The function definition does not need to specify the parameter type, the interpreter automatically infers the
return value type, if there is no clear return value, the default return value is none
print() can be used to print a blank line
4. Parameter passing and parameter default values
def dup(str,times=2): #给出了一个默认值
print(str*times)
Python stipulates that although optional parameters must be placed after non-optional parameters
5. The return value of the function
Can return one or more values, the return value can be a variable, an expression,
or no return value
6.lamada function (concise code usage)
The lamada reserved words are used to define anonymous functions (also known as lamada functions).
An anonymous function does not have a name, but returns the function name as the result of the
function. The definition of an anonymous function is equivalent to the following form as a normal function
def 函数名 (参数列表）:
return 表达式
Simply put, the lamada function is used to define a simple function that can be expressed in one line and returns a function type
f=lamada x,y: x+y#返回x+y的值
Features of lamada function:
simplify the code, but reduce the readability
. An anonymous function is defined, which
will not increase efficiency.
If it can be implemented with for ……in…… if, lamada function is
not used. If lamada function is used, do not include loops in the function. If so, it is recommended to define a function to complete
7. Variable parameter transfer (variable number of transferred parameters)
def <函数名> (<参数> ,*b):
函数体
返回值
*b is the name of the variable defined by yourself, b can be called anything
8. Global variables and local variables
2. Class and Object
The concept of objects in python is very broad, everything can be called an object, not necessarily an instance of a certain class. Built-in data types such as dictionaries, strings, lists, and tuples all have completely similar syntax and usage.
Such as:
"abc".split()
1. Definition of class
class 类名:
方法定义
2. Class object
Class objects support two operations: attribute reference and instantiation.
Attribute references have the same standard syntax as all attribute references in Python: After the obj.name
class object is created, all names in the class namespace are valid attribute names.
