attribute
1. Class attribute
a. Variables directly defined in a class are class attributes
b. How to use: call in the way of 'class.'
c. When to use: attributes are not different because of different objects
2. Object properties
a. Defined in the form of 'self. Attribute name = value'__ init __ Method
b. Use as an 'object.'
c. When to use: attributes vary from object to object
class Rect:
side = 4 # Class properties
def __init__(self, width, height):
self.width = width # Object properties
self.height = height
3. Initial value of object attribute
1) Assign a fixed value
class Rect:
side = 4 # Class properties
def __init__(self):
self.width = 3 # Object properties
self.height = 4
2) Use parameters without default values
class Rect:
side = 4 # Class properties
def __init__(self, width, height):
self.width = width # Object properties
self.height = height
3) Parameters using default values
class Rect:
side = 4 # Class properties
def __init__(self, width=3, height=4):
self.width = width # Object properties
self.height = height
method
1. Object method
How to define: functions defined directly in a class
How to call: object
Features: there is a default parameter self. When calling with an object, it does not pass parameters and points to the current object.
When to use: to realize the function of a function, you need to use the object method
2. Class method
How to define: add decorator before defining function: @ classmethod
How to call: class
Features: there is a default parameter cls, which does not need to pass parameters when calling, and points to the current class.
When to use: when objects are not needed, classes are needed to implement functions
3. Static method
How to define: add @ staticmethod before defining a function
How to call: class
Features: no default parameters
When to use: neither objects nor classes are required to implement the function of a function
class Test:
def func1(self):
print('Object method')
@classmethod
def func2(cls):
print('Class method')
@staticmethod
def func3():
print('Static method')
test = Test()
test.func1() # Object method
Test.func2() # Class method
Test.func3() # Static method
4. Add, delete, modify and query object attributes
class Poker:
def __init__(self,color,num):
self.color=color
self.num=num
def show_card(self):
print(f'{self.color}{self.num}')
poker =Poker('heart','K')
poker.show_card()
# Add object properties
poker.age=18
print(poker.age) # 18
# Delete object properties
del poker.color
# print(poker.color) #report errors
poker.age=21
print(poker.age) # 21
inherit
1. Succession
Inheritance is to let subclasses directly own the properties and methods of the parent class
Subclass - successor
Parent - inheritee
2. How to create inheritance relationship
class Class name(Parent class):
Class description document
Class content
class Person:
def __init__(self):
self.name = 'Xiao Ming'
self.age = 18
self.gender = 'male'
class Student(Person):
def __init__(self):
super().__init__()
self.subject = 'Python'
pass
student = Student()
print(student.name, student.age, student.gender) # Xiao Ming 18 male
print(student.subject) # Python
3. Subclass addition
1) Add class properties and methods
Define a new class directly in a subclass
2) Add object properties
In subclass__ init __ Use super () inside__ init __ () call the initialization method of the parent class
Method calls in class:
First, check whether there is a corresponding method in the current class. If there is a direct call, it depends on whether there is a corresponding method in the parent class,
An error will not be reported until the object class is not found
time module
1.time() - get the current time (the timestamp is returned)
Time stamp: time is expressed by time difference (from 0:00:00:00 GMT on January 1, 1970, in seconds)
# 2021/10/29/19/19 t=time.time() # 1635506350.5123148
2.localtime() - get the local time of the current time (return the time structure)
Localtime (timestamp) - converts the timestamp to the structure time corresponding to the local time
t2=time.localtime() print(t2) ''' time.struct_time(tm_year=2021, tm_mon=10, tm_mday=29, tm_hour=19, tm_min=20, tm_sec=52, tm_wday=4, tm_yday=302, tm_isdst=0) ''' t2=time.localtime(1625006350) print(t2) ''' time.struct_time(tm_year=2021, tm_mon=6, tm_mday=30, tm_hour=6, tm_min=39, tm_sec=10, tm_wday=2, tm_yday=181, tm_isdst=0) '''
3. Conversion between structure time and string
Time.strftime (time format, time structure)
t3=time.strftime('%Y year%m month%d day %H:%M:%S',t2)
print(t3) # June 30, 2021 06:39:10
t3=time.strftime('%Y-%m-%d %p %I:%M:%S',t2)
print(t3) # 2021-06-30 AM 06:39:10
t3=time.strftime('%m-%d %A',t2)
print(t3) # 06-30 Wednesday
t3=time.strftime('%B %A',t2)
print(t3) # June Wednesday
t3=time.strftime('%Y year%m month%d day',t2)
print(t3) # June 30, 2021
Time.strptime (string time, time format)
t3_str='2012 March 17' t3=time.strptime(t3_str,'%Y year%m month%d day') print(t3) ''' time.struct_time(tm_year=2012, tm_mon=3, tm_mday=17, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=5, tm_yday=77, tm_isdst=-1) '''
4. Convert structure time to timestamp
Mktime (structure time)
''' t3: time.struct_time(tm_year=2012, tm_mon=3, tm_mday=17, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=5, tm_yday=77, tm_isdst=-1) ''' t4=time.mktime(t3) print(t4) # 1331913600.0