代替if else的方法

以下是几种代替if else语句的方法：

1.使用字典映射：

def dispatch_if(operator, x, y):
    if operator == 'add':
        return x + y
    elif operator == 'sub':
        return x - y
    elif operator == 'mul':
        return x * y
    elif operator == 'div':
        return x / y
    else:
        return None

def dispatch_dict(operator, x, y):
    return {
        'add': lambda: x + y,
        'sub': lambda: x - y,
        'mul': lambda: x * y,
        'div': lambda: x / y,
    }.get(operator, lambda: None)()

print(dispatch_if('add', 2, 8)) # 输出：10
print(dispatch_dict('add', 2, 8)) # 输出：10

2.使用多态：

class Operator:
    def operate(self, x, y):
        pass

class AddOperator(Operator):
    def operate(self, x, y):
        return x + y

class SubOperator(Operator):
    def operate(self, x, y):
        return x - y

class MulOperator(Operator):
    def operate(self, x, y):
        return x * y

class DivOperator(Operator):
    def operate(self, x, y):
        return x / y

def dispatch_polymorphism(operator, x, y):
    return operator.operate(x, y)

print(dispatch_polymorphism(AddOperator(), 2, 8)) # 输出：10

3.使用函数映射：

def add(x, y):
    return x + y

def sub(x, y):
    return x - y

def mul(x, y):
    return x * y

def div(x, y):
    return x / y

def dispatch_func(operator, x, y):
    return {
        'add': add,
        'sub': sub,
        'mul': mul,
        'div': div,
    }.get(operator, lambda x, y: None)(x, y)

print(dispatch_func('add', 2, 8)) # 输出：10

4.使用try...except：

def dispatch_try(operator, x, y):
    try:
        return {
            'add': x + y,
            'sub': x - y,
            'mul': x * y,
            'div': x / y,
        }[operator]
    except KeyError:
        return None

print(dispatch_try('add', 2, 8)) # 输出：10