类
基础
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class Dog(): """test""" def __init__(self, name, age): """初始化""" self.name = name self.age = age def sit(self): """蹲""" print(self.name.title() + " is now sitting") def roll_over(self): print("roll over") |
- python里面，类的首字母要大写。
""""""对功能进行描述，相对于注释__init__是一个特殊的方法，每当根据类Dog创建新实例时，python会自动运行它。- 形参self必不可少，而且要位于所有参数的前面，python创建Dog的实例化的时候，会自动传入实参self，self是指向实例本身的引用，让实例能够访问类中的方法。
- 以self为前缀的变量都可供类中的所有方法使用。
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// python 2.7中创建类 class ClassName(object): --snip class Dog(object): --snip |
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class Dog(): --snip my_dog = Dog('white', 6) print("My dog's name is " + my_dog.name.title() + ".") // 调用方法 my_dog.sit() my_dog.roll_over() // 多个实例 my_dog_other = Dog('test', 3) |
默认值
- 如test属性
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class Car(): """car""" def __init__(self, name, mode, year): """attr""" self.name = name self.mode = mode self.year = year self.test = 0 my_car = Car('tes', 'manal', 2022) my_car.test = 10 |
继承
- 一个类继承一个类时，它将自动获得另一个类的所有属性和方法
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class Car(): """父类""" def __init__(self, name, mode, year): self.name = name self.mode = mode self.year = year --snip // 从Car继承 class ElectricCar(Car): """heri from Car""" def __init__(self, name, mode, year): super().__init__(name, mode, year) |
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// 2.7中的继承 class Car(object): def __init__(self, name, year): -- snip class ElectricCar(Car): def __init__(self, name, year): super(Electric, slef).__init__(name, year) -- snip |
重写父类方法
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class Car(): """父类""" def __init__(self, name, mode, year): self.name = name self.mode = mode self.year = year def print_name(): print(self.name) class ElectricCar(Car): def __init__(self, name, mode, year): self.electric = True def print_name(): print("Electric car named " + self.name) |
类的导入
- car.py
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class Car(): def __init__(self, name, mode, year): self.name = name self.mode = mode self.year = year def print_name(): print(self.name) class ElectricCar(Car): def __init__(self, name, mode, year): self.electric = True def print_name(): print("Electric car named " + self.name) |
- my_car.py
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from car import Car my_new_car = Car('audi', 'car', 2022) |
- 导入多个类
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from car import Car, ElectricCar |
- 导入整个模块
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from car |
- 导入整个模块中的所有类
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from module_name import * |
- 模块间的导入以及使用
car.py
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class Car(): def __init__(self, name, mode, year): self.name = name self.mode = mode self.year = year def print_name(): print(self.name) |
electriccar.py
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from car import Car class ElectricCar(Car): def __init__(self, name, mode, year): self.electric = True def print_name(): print("Electric car named " + self.name) |
my_car.py
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from car import Car form electriccar import ElectricCar // ... |
标准库
文件
读取
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with open('pi.txt') as file_object: contents = file_object.read() print(contents) -- 取空格 -- print(contents.rstrip()) // Linux with open('files/filename.txt') as file_object: // Windows with open('files\filename.txt') as file_object: |
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// 逐行读取 file_name = 'pi.txt' with open(file_name) as file_object: for line in file_object: print(line) // print(line.rstrip()) |
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// 把文件每行放到一个列表里面 file_name = 'test.txt' with open(filename) as file_obect: lines = file_object.readlines() for line in lines: print(line.rstrip()) |
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// 把文件内容读取到内存 filename = 'pi.txt' with open(filename) as file_object: lines = file_object.readlines() pi_string = '' for line in lines: pi_string += line.rstrip() print(pi_string) print(len(pi_string)) // 查询 test = '2313' if test in pi_string: print("yes") else: print("no") |
写入
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filename = "test.txt" with open(filename, 'w') as file_object: file_object.write("it's a test.") // 写入多行 with open(filename, 'w') as file_object: file_object.write("it's a test1.") file_object.write("it's a test2.") // 附加 with open(filename, 'a') as file_object: file_object.write("it's a test1.") |
异常
- python使用被称为异常的对象来管理程序执行期间发生的错误。
- 每当发生让python不知所措的错误时，它都会创建一个异常对象。
如果编写了处理该异常的代码，程序将继续运行。如果未对异常进行处理，程序将停止，并显示一个traceback。
ZeroDivisionError
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try: print(5/0) except ZeroDivisionError: print("You can't divide by zero") |
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while True: first_number = input("\nFirst number:") if first_number == 'q': break second_number = input("\nSecond number:") try: anwser = int(first_number) / int(second_number) except ZeroDivisionError: print("you can't divide by zero") else: print(anwser) |
FileNotFoundError
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filename = "pi.txt" try: with open(filename) as file_object: contents = file_object.read() except FileNotFoundError: msg = "sorry, the file" + filename + "does not found" print(msg) |
Json
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// json.dump() // json.load() |
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