CODEWITHSUNDEEP
pythontype-hintingmypy
MRocklin
MRocklin

Reputation: 57271

Build type information about attributes into superclass for type hinting

So I have a couple classes that share common attributes

class Person(object):
    def __init__(self, name, age, income):
        self.name = name
        self.age = age
        self.income = income

class Pet(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age

I want to make a superclass for these objects

class Animal(object):
    ...

So that I can refer to this type in functions and get type hints from my IDE

def f(x: Animal):
    x.name<tab>  # I expect to see that this thing is a string type

Or have nice static analysis from projects like mypy.

What is the best way for me to write my classes to achieve this behavior?

Upvotes: 0

Views: 124

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1121864

As of Python 3.6 you can use variable annotations:

class Animal(object):
    name: str
    age: int
    income: int

These are not class attributes; they specify the types for instance attributes.

From the specification:

Type annotations can also be used to annotate class and instance variables in class bodies and methods. In particular, the value-less notation a: int allows one to annotate instance variables that should be initialized in __init__ or __new__.

Upvotes: 3

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