如何定义一个新的type（）

Question

class Something:

    def __init__(self, x, y=0):

        self.x = x
        self.y = y

x is a string and y is a currency number. How can i define a new type such that

type(self.y) == Currency

Answer 1

Define a Currency class like this:

class Currency(object):
     def __init__(self, value):
             self.value = value

Then you can create a new variable of type Currency like this:

y = Currency(3)

Answer 2

For simple classes(no logic, only data), you can also use dataclasses . This is available in python 3.7

from dataclasses import dataclass

@dataclass
class Currency:
     value: int

For older versions, you can use namedtuple

from collections import namedtuple

Currency = namedtuple('Currency', ['value'])