Python 3 dictionary with known keys typing

Question

I'm using Python 3 typing feature for better autocomplete.

Many times I have functions that return key/value (dictionary) with specific keys. super simple example:

def get_info(name):
    name_first_letter = name[0]
    return {'my_name': name, 'first_letter': name_first_letter}

I want to add type hinting to this function to tell others who use this function what to expect.

I can do something like:

 class NameInfo(object):
     def __init__(self, name, first_letter):
         self.name = name
         self.first_letter = first_letter

and then change the function signature to:

def get_info(name) -> NameInfo:

But it requires too much code for each dictionary.

What is the best practice in that case?

question from:https://stackoverflow.com/questions/44225788/python-3-dictionary-with-known-keys-typing

Answer 1

As pointed out by Blckknght, you and Stanislav Ivanov in the comments, you can use NamedTuple:

from typing import NamedTuple


class NameInfo(NamedTuple):
    name: str
    first_letter: str


def get_info(name: str) -> NameInfo:
    return NameInfo(name=name, first_letter=name[0])

Starting from Python 3.8 you can use TypedDict which is more similar to what you want:

from typing import TypedDict


class NameInfo(TypedDict):
    name: str
    first_letter: str


def get_info(name: str) -> NameInfo:
    return {'name': name, 'first_letter': name[0]}