一.构造函数与析构函数
构造方法: def _ init _(self) 在实例化对象时自动执行。
析构方法:def _ def _(self) 当删除对象时,自动调用的方法。
class Animal(object):
# 实例化对象时自动执行
def __init__(self, name, age):
# 把属性和对象名绑定在一起, 便于访问对象的属性.
self.name = name
self.age = age
print("创建对象成功.......")
# 析构函数, 当你删除对象时, 自动调用的方法。
# del 对象名或者程序执行结束之后
def __del__(self):
print("删除对象成功.......")
if __name__ == '__main__':
# 创建对象
cat = Animal('tom', 78)
#删除对象
del cat
print(cat)
二.__str__
、__repr__
str和repr都是对对象的字符串显示, 使用场景不同.
如果没有_str_的时候, 自动调用_repr_方法的内容.
class People(object):
# 实例化对象时自动执行
def __init__(self, name, age):
# 把属性和对象名绑定在一起, 便于访问对象的属性.
self.name = name
self.age = age
print("创建对象成功.......")
# 析构函数, 当你删除对象时, 自动调用的方法。
# del 对象名或者程序执行结束之后
def __del__(self):
print("删除对象成功.......")
# __str__和__repr__都是对对象的字符串显示, 使用场景不同.
# 如果没有__str__的时候, 自动调用__repr__方法的内容.
def __str__(self):
# print(对象名) print(str(对象名))
# print('People(%s, %d)' %(self.name, self.age))
return 'People(%s, %d)' %(self.name, self.age)
def __repr__(self):
# print(repr(对象名)) 或者交互式环境中直接: 对象名
return "People(%s)" %(self.name)
if __name__ == '__main__':
# 创建对象
p1 = People('messi', 31)
print(p1)
print(str(p1))
print(repr(p1))
三.字符串的format
方法
1. 通过位置填充字符串
# 通过位置填充字符串
print("name:{0}, age:{1}, scores:{2}".format('villa', 10, [99, 100, 101]))
print("name:{0}, age:{1}, scores:{0}".format('villa', 10))
print("name:{0}, id:{1:.4f}, scores:{0}".format('villa', 3.14159265354))
2.通过key值填充字符串
# # 通过key值填充字符串
d = {'max': 100, 'min': 10}
print("MAX: {max}, MIN:{min}".format(max=100, min=10))
print("MAX: {max}, MIN:{min}".format(**d))
3.通过下标或者索引值填充
# # 通过下标或者索引值填充
point = (3,4)
print("x:{0[0]}, y:{0[1]}".format(point))
4.面向对象中的使用
# 面向对象操作
class Book(object):
def __init__(self, name, author, state, bookIndex):
self.name = name
self.author = author
# 0:'已借出' 1:'未借出'
self.state = state
self.bookIndex = bookIndex
def __str__(self):
return 'Book(%s, %d)' %(self.name, self.state)
book1 = Book('python', 'guido', 1, 'IND444')
book2 = Book('java', 'Sun', 1, 'IND445')
print("name:{b.name}, state:{b.state}, bookIndex:{b.bookIndex}".format(b=book1))
print("name:{0.name}, state:{0.state}, author:{1.author}".format(book1,book2))
四.__format__
魔术方法
formats = {
'ymd':"{d.year}-{d.month}-{d.day}",
'mdy':"{d.month}/{d.day}/{d.year}",
}
class Date(object):
def __init__(self, year, month, day):
self.year = year
self.month = month
self.day = day
# format方法: format(对象名)时自动调用
def __format__(self, format_spec=None):
# return "这是显示format的内容"
# if format_spec:
# format_spec = format_spec
# else:
# format_spec = 'ymd'
if not format_spec:
format_spec = 'ymd'
fmt = formats[format_spec] # "{d.year}-{d.month}-{d.day}".format(d=d)
return fmt.format(d=self)
简化版本
class Date(object):
def __init__(self, year, month, day):
self.year = year
self.month = month
self.day = day
# format方法: format(对象名)时自动调用
def __format__(self, format_spec=None):
if not format_spec:
return "%s-%s-%s" %(self.year, self.month, self.day)
else:
if format_spec == 'ymd':
return "%s-%s-%s" %(self.year, self.month, self.day)
elif format_spec == 'dmy':
return "%s/%s/%s" %(self.day, self.month, self.year)
else:
return "error format"
d = Date(2019, 8, 25)
print(format(d))
print(format(d, 'ymd'))
print(format(d, 'dmy'))
五.类内部装饰器@property
将类方法变成类属性,使调用类中的方法像引用类中的字段属性一样。被修饰的特性方法,内部可以实现处理逻辑,但对外提供统一的调用方式。遵循了统一访问的原则。
class Book(object):
def __init__(self, name, author, state, bookIndex):
self.name = name
self.author = author
# 0:'已借出' 1:'未借出'
self.__state = state
self.bookIndex = bookIndex
# 将类方法变成类属性
# 使用时, 没有装饰器b.state()
# 使用时, 有装饰器b.state
@property
def state(self):
if self.__state == 0:
return '已借出'
elif self.__state == 1:
return '未借出'
else:
return "状态异常"
# 当修改属性state时, 自动执行下面的方法; b.state = 10
#setter实现了通过属性x来对私有变量_x进行操作
@state.setter
def state(self, value):
# if value == 0 or value == 1:
if value in (0,1):
# 更新书籍的状态
self.__state = value
#deleter实现了通过属性x来对私有变量_x进行操作
@state.deleter
def state(self):
print("is deleteing......")
def __str__(self):
return 'Book(%s, %d)' %(self.name, self.__state)
b = Book('Gaopin', 'ZhangSW', 1, 'WES523')
# print(b.state)
#
# # 1). 书籍的状态可以人以改变, 并不能限制只能为0或者1;
# 2). 书籍状态如何友好的显示?
# b.state = 10
# print(b.state)
# 3). 问题解决, 但是调用比较复杂, 可读性不高.
# print(b.get_state())
# print(b.set_state(10))
# print(b.get_state())
# 4).
print(b.state)
b.state = 0
print(b.state)
del b.state
六.类的切片与索引
class Student(object):
def __init__(self, name, scores):
self.name = name
self.scores = scores
# 支持索引、切片; s[key]
def __getitem__(self, key):
# print("获取索引对应的value值")
return self.__dict__[key]
# s[key] = 修改的值
def __setitem__(self, key, value):
self.__dict__[key] = value
# del s[key] 根据索引删除某个值
def __delitem__(self, key):
del self.__dict__[key]
def hello(self):
return "hello"
s = Student('westos', [101, 100, 100])
print(s[0])
print(s[1])
print(s[2])
# 0, 200
s[0] = 200
print(s[0])
print(s.scores)
del s[0]
print(s.scores)
print(s[1:3])
s[1:3] = [0,0]
print(s[:])
del s[:-1]
print(s[:])
print(s[0])
七.类的重复与连接的实现
from collections import Iterable
class Student(object):
def __init__(self, name, scores):
self.name = name
self.scores = scores
self.power = 100
# obj1 + obj2
def __add__(self, other):
# 更新self对象的power属性值;
self.power = self.power + other.power
return self
# obj1 * 3
def __mul__(self, other):
# *的效果是, 能量*power
return self.power * other
# 成员操作符; item in obj1
def __contains__(self, item):
return item in self.scores
# 可以for循环迭代
def __iter__(self):
"""
iter([1,2,3,4,5])
<list_iterator object at 0x7f6e1f51ffd0>
iter({1,2,3,4,5})
<set_iterator object at 0x7f6e1f567318>
"""
# 迭代返回的是成绩
return iter(self.scores)
def __repr__(self):
return "Student:%s,%s" %(self.name, self.power)
s1 = Student('westos1', [101,100,100])
s2 = Student('westos2', [100,100,100])
s3 = Student('westos3', [100,100,100])
# 连接的实现;
print(s1 + s2 + s3)
# 重复:
a = 3; print(a*3)
s = 'a'; print(s*3)
li = [1,2,3]; print(li*3)
print(s1*3)
# 成员操作符
print(s1.scores)
print(200 in s1)
print(100 in s1)
print(200 not in s1)
print(100 not in s1)
# for循环迭代
for i in s1:
print(i)
print(isinstance(s1, Iterable))
八.类中长度的比较
class Student(object):
def __init__(self, name, scores, power):
self.name = name
self.scores = scores
self.power = power
def __add__(self, other):
# 更新self对象的power属性值;
self.power = self.power + other.power
return self
# obj1 > obj2
def __gt__(self, other):
return self.power > other.power
# obj >= obj2
__ge__ = lambda self, other: self.power >= other.power
# obj1 == obj2
def __eq__(self, other):
return self.power == other.power
def __ne__(self, other):
return self.power != other.power
# return not self.__eq__(other)
def __repr__(self):
return "Student:%s,%s" %(self.name, self.power)
def __len__(self):
return len(self.scores)
s1 = Student('westos1', [101,100,100], 100)
s2 = Student('westos2', [100,100,100], 101)
s3 = Student('westos3', [100,100,100], 80)
print(s1+s2)
print(s1 > s2 > s3)
print(s1>=s2)
print(s1<s2)
print(s1 == s2)
print(s1 != s2)
print(len(s1))
九.类方法与静态方法
1.类方法@classmethod
默认传递类本身给这个方法;
如果使用原本的方法传递给类,是只能传递一个一个数,无法传递一个整体
所以调用classmethod,将传入值进行处理后,把返回值传入__init__
进行数值初始化.
class Date(object):
def __init__(self, year, month, day):
self.year = year
self.month = month
self.day = day
# echo普通方法, 默认情况下会传递对象给echo
def echo(self):
return "%s %s %s" %(self.year, self.month, self.day)
@classmethod
def as_string(cls, s):
print(cls)
month, day, year = s.split('/')
d = cls(year, month, day)
return d
s = '10/10/2018'
print(Date.as_string(s).echo())
2.静态方法
默认python解释器不会传递任何参数
class Date(object):
def __init__(self, year, month, day):
self.year = year
self.month = month
self.day = day
# 默认python解释器不会传递任何参数
@staticmethod
def is_vaild(s):
# 批量将年月日转换成整形(列表生成式, map)
# month, day, year = s.split('/')
# month, day, year = [int(i) for i in s.split('/')]
month, day, year = map(int, s.split('/'))
return 0 < month <= 12 and 0 < day <= 31 and 1 < year < 9999
s = '10/10/2018'
print(Date.is_vaild(s))
十.,面向对象的反射机制
1.显示对象所拥有的方法和属性
print(dir(str))
f = open('hello.txt')
print(dir(f))
2.判断对象所属的类
class Student(object):
"""
这是student类的帮助文档
"""
def __init__(self, name, age):
self.name = name
self.__age = age
def get_score(self):
return "score"
def get_grade(self):
return 'grade'
s1 = Student("fentiao", 10)
print(type(s1))
print(isinstance(s1, Student))
print(isinstance('hello', Student))
3. 跟据对象可以获取的内容
class Student(object):
"""
这是student类的帮助文档
"""
def __init__(self, name, age):
self.name = name
self.__age = age
def get_score(self):
return "score"
def get_grade(self):
return 'grade'
s1 = Student("villa", 35)
print(s1.__class__)
print(s1.__dict__)
print(s1.__doc__)
4. hasattr
, getattr
, setattr
, delattr
# hasattr: 判断对象是否包含对应的属性或者方法名;
print(hasattr(s1, 'name'))
print(hasattr(s1, '__age')) # 私有属性, 私有方法, 是不能判断的;
print(hasattr(s1, 'score'))
print(hasattr(s1, 'get_score'))
print(hasattr(s1, 'set_score'))
# getattr: 用于返回对象的属性值或者方法名对应的方法体;
print(getattr(s1, 'name'))
print(getattr(s1, '__age', 'no attr'))
print(getattr(s1, 'get_score', 'no method')) # 获取方法名, 如果要执行方法, 直接调用即可
print(getattr(s1, 'set_score', 'no method')) # 获取方法名, 如果要执行方法, 直接调用即可
# setattr:
# 修改某个属性的值
setattr(s1, 'name', 'westos')
print(getattr(s1, 'name'))
# 添加某个属性及对应的值;
setattr(s1, 'score', 100)
print(getattr(s1, 'score'))
# 修改方法
def get_score1():
return "这是修改的方法内容"
setattr(s1, 'get_score', get_score1)
print(getattr(s1, 'get_score')())
def set_score():
return "这是添加的方法"
# 添加方法
setattr(s1, 'set_score', set_score)
print(getattr(s1, 'set_score')())
# delattr
delattr(s1, 'name')
print(hasattr(s1, 'name'))
print(hasattr(s1, 'set_score'))
delattr(s1, 'set_score')
print(hasattr(s1, 'set_score'))