I am adding type annotations to a lot of code to make it clear to other devs what my functions and methods do. How would I type annotate a function that takes JSON data in as an argument, and returns JSON data?
(very simplified version)
def func(json_data):
return json_data
what I want to do but with JSON instead of int:
def add_nums(a: int, b: int) -> int:
return a+b
Json objects are usually like a bag of items. It can have numbers, string, floats, list and nested json objects. If you wish to deep dive into JSON body actual structure then following Option1 & 2 can assist you or you can do the 3 rd step.
First Option: Please check this Python3 docs links.
If you can clearly define your json body then you can use following example.
from collections.abc import Sequence
ConnectionOptions = dict[str, str]
Address = tuple[str, int]
Server = tuple[Address, ConnectionOptions]
def broadcast_message(message: str, servers: Sequence[Server]) -> None:
...
# The static type checker will treat the previous type signature as
# being exactly equivalent to this one.
def broadcast_message(
message: str,
servers: Sequence[tuple[tuple[str, int], dict[str, str]]]) -> None:
...
Second Option: you can also define you own custom type classes to work with, unlike above where you create lots of global items.
https://docs.python.org/3/library/typing.html#newtype
from typing import NewType
UserId = NewType('UserId', int)
some_id = UserId(524313)
def get_user_name(user_id: UserId) -> str:
...
Third Option: Like the above suggested answers, using a str is simple approach. Treat you json body as string and using json modules to convert it to string & viceversa
Fourth Option: Using a Library to define your classes - https://marshmallow.readthedocs.io/en/stable/
If you are working on Apache Spark then https://github.com/ketgo/marshmallow-pyspark is worth knowing about.