创建用Python打印整数的装饰器

Question

I'd like to create a decorator that prints units on a number.

money = 10
print(money)

results in '10 dollars'

money = 1
print(money)

results in '1 dollar'

I get that I need to wrap money.__str__() , but I'm not sure how to do that generically with a decorator.

Am I on the right track here? Can the following somehow become a decorator?

def str_cur(money):
    if money == 1 or money == -1:
       return f"{money} dollar"
    else
       return f"{money} dollars"

Answer 1

Decorators in Python apply to functions (and more rarely, classes), not to variables. So I think investigating their syntax is not going to help you.

It sounds like you might be able to do what you want by creating a class for your money that wraps up the integer. Your class can have a __str__ method that includes the currency name along with the number:

class Dollars(int):
    def __str__(self):
        if abs(self) == 1:
            return f"{self} dollar"
        else
            return f"{self} dollars"

Now you could do:

money = Dollars(10)
print(money) # prints "10 dollars"

The Dollar class I wrote above inherits from int , so you can do all the normal numerical operations on it, but you will often get a normal int object back instead of another Dollar instance. If you want to only get dollars back, you'd need to write your own versions of the numeric methods, which alas is rather tedious (you'd probably want to stop inheriting from int and just have an integer attribute). If you only need to support a limited number of numeric options (like adding and subtracting dollar amounts from each other and multiplying and dividing by integers) it might not be too bad.