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Detailed explanation explains the inheritance of Python classes in detail
- 迷茫Original
- 2017-03-25 17:50:181624browse
Inheritance of Python classes (Advanced 5)
1. What is inheritance in python
What is inheritance in python:
New Classes do not have to be written from scratch
The new class inherits from the existing class and automatically has all the functions of the existing class
The new class only Need to write new features that are missing from existing classes
Benefits of inheritance:
Reuse existing code
Automatically possess all the functions of existing classes
Only need to write the missing new functions
Inherited features:
The subclass and the parent class are in an is relationship
Characteristics of python inheritance:
Always start from A class inherits
Don’t forget to call super().init
2. Inheriting a class in python
class Person(object):
def init(self, name, gender):
self.name = name
self.gender = gender
class Teacher(Person):
def init(self, name, gender, course):
super(Teacher, self).init(name, gender)
self.course = course
t = Teacher('Alice', 'Female', 'English')
print t.name
print t.course3. Determining the type in python
The function isinstance() can determine the type of a variable. It can be used in Python’s built-in data types such as str, list, and dict, and can also be used in our Custom classes, they are essentially data types.
class Person(object):
def init(self, name, gender):
self.name = name
self.gender = gender
class Student(Person):
def init(self, name, gender, score):
super(Student, self).init(name, gender)
self.score = score
class Teacher(Person):
def init(self, name, gender, course):
super(Teacher, self).init(name, gender)
self.course = course
t = Teacher('Alice', 'Female', 'English')
print isinstance(t, Person)
print isinstance(t, Student)
print isinstance(t, Teacher)
print isinstance(t, object)4. Polymorphism in python
class Person(object):
def init(self, name, gender):
self.name = name
self.gender = gender
def whoAmI(self):
return 'I am a Person, my name is %s' % self.name
class Student(Person):
def init(self, name, gender, score):
super(Student, self).init(name, gender)
self.score = score
def whoAmI(self):
return 'I am a Student, my name is %s' % self.name
class Teacher(Person):
def init(self, name, gender, course):
super(Teacher, self).init(name, gender)
self.course = course
def whoAmI(self):
return 'I am a Teacher, my name is %s' % self.name
import json
class Students(object):
def read(self):
return r'["Tim", "Bob", "Alice"]'
s = Students()
print json.load(s)5. Multiple inheritance in python
In addition to inheriting from one parent class, Python allows inheritance from multiple parent classes, called for multiple inheritance. Java cannot have multiple inheritance
class A(object):
def init(self, a):
print 'init A...'
self.a = a
class B(A):
def init(self, a):
super(B, self).init(a)
print 'init B...'
class C(A):
def init(self, a):
super(C, self).init(a)
print 'init C...'
class D(B, C):
def init(self, a):
super(D, self).init(a)
print 'init D...'
class Person(object):
pass
class Student(Person):
pass
class Teacher(Person):
pass
class SkillMixin(object):
pass
class BasketballMixin(SkillMixin):
def skill(self):
return 'basketball'
class FootballMixin(SkillMixin):
def skill(self):
return 'football'
class BStudent(BasketballMixin):
pass
class FTeacher(FootballMixin):
pass
s = BStudent()
print s.skill()
t = FTeacher()
print t.skill()6. Obtaining object information in python
In addition to using isinstance() to determine whether it is an instance of a certain type, is there any other way to obtain more What about the information?
First, you can use the type() function to get the type of the variable, which returns a Type object.
dir() function gets all the attributes of the variable.
The attributes returned by dir() It is a list of strings. If an attribute name is known, to get or set the attributes of the object, you need to use the getattr() and setattr() functions
class Person(object):
def init(self, name, gender):
self.name = name
self.gender = gender
class Student(Person):
def init(self, name, gender, score):
super(Student, self).init(name, gender)
self.score = score
def whoAmI(self):
return 'I am a Student, my name is %s' % self.name
print type(123) # <type 'int'>
s = Student('Bob', 'Male', 88)
print s # <class 'main.Student'>
print dir(123) # ['abs', 'add', 'and', 'class', 'cmp', 'coerce', 'delattr', 'p', 'pmod', 'doc', 'float', 'floorp', 'format', 'getattribute', 'getnewargs', 'hash', 'hex', 'index', 'init', 'int', 'invert', 'long', 'lshift', 'mod', 'mul', 'neg', 'new', 'nonzero', 'oct', 'or', 'pos', 'pow', 'radd', 'rand', 'rp', 'rpmod', 'reduce', 'reduce_ex', 'repr', 'rfloorp', 'rlshift', 'rmod', 'rmul', 'ror', 'rpow', 'rrshift', 'rshift', 'rsub', 'rtruep', 'rxor', 'setattr', 'sizeof', 'str', 'sub', 'subclasshook', 'truep', 'trunc', 'xor', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real']
print dir(s) # ['class', 'delattr', 'dict', 'doc', 'format', 'getattribute', 'hash', 'init', 'module', 'new', 'reduce', 'reduce_ex', 'repr', 'setattr', 'sizeof', 'str', 'subclasshook', 'weakref', 'gender', 'name', 'score', 'whoAmI']
print getattr(s, 'name') # Bob
setattr(s, 'name', 'Adam')
print s.name # Adam
class Person(object):
def init(self, name, gender, **kw):
self.name = name
self.gender = gender
for k, v in kw.iteritems():
setattr(self, k, v)
p = Person('Bob', 'Male', age=18, course='Python')
print p.age # 18
print p.course #PythonThe above is the detailed content of Detailed explanation explains the inheritance of Python classes in detail. For more information, please follow other related articles on the PHP Chinese website!