魔法函数

什么是魔法函数？

1）在python中以双下滑线开头并且以双下滑线结尾的函数

2）魔法函数可以随意定义某个类的特性，这些方法在进行特定的操作时会自动被调用

普通的遍历

class Company(object):
    def __init__(self, employee_list):
        self.employee = employee_list

company = Company(["tom", "bob", "jane"])

emploee = company.employee
for em in emploee:
    print(em)

运行结果

实现 getitem （变为可迭代类型）

class Company(object):
    def __init__(self, employee_list):
        self.employee = employee_list

    def __getitem__(self, item):
        return self.employee[item]

company = Company(["tom", "bob", "jane"])

for em in company:
    print(em)

运行结果

Python的数据模型以及数据模型对Python的影响

class Company(object):
    def __init__(self, employee_list):
        self.employee = employee_list

    def __getitem__(self, item):
        return self.employee[item]

company = Company(["tom", "bob", "jane"])
company1 = company[:2]
for em in company1:
    print(em)

也可利用 __getitem__成为序列类型，使用切片

实现__len__获取长度

class Company(object):
    def __init__(self, employee_list):
        self.employee = employee_list

    def __len__(self):
        return len(self.employee)

company = Company(["tom", "bob", "jane"])
print(len(company))

3.3 python魔法函数一览