Define custom type hint with lists in Python 3.6

Question

I am trying to define a new type hint, however, it will not let me do this in Python 3.6 and I was wondering if there is any way around it. Here is my example code where I want my own class which takes a list as a field:

class T(type):

    def __new__(cls, nums):
        return super().__new__(cls, f'T((nums))', (T,),{})

    def __init__(self, nums):
        self.__origin__ = T
        self.__args__ = nums

whenever I try to actually use this, I get

'type' object is not subscriptable

If I define a custom type hint that does not involve a list, the code works. Is there anyway I can define a custom type hint in python3.6?

Debdut Goswami · Accepted Answer · 2021-06-29 20:36:54Z

2

You need to understand that type hints are for objects (or datatypes). You can not create a custom class inheriting from type. If you want to create a new datatype, then simply inherit from object. Although, even inheriting from object is not necessary as everything is an object in python but it is generally considered as a good practice.

class T(object):
  def __init__(self, val):
    self.__val = val

  def __str__(self):
    return self.__val

t = T(10)
print(t) # 10
print(type(t)) # <class '__main__.T'>

answered Jun 29, 2021 at 20:36

Debdut Goswami

1,3791 gold badge14 silver badges32 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Define custom type hint with lists in Python 3.6

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related