marshmallow-code/marshmallow

Type hinting for `load` is too strict

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#1,457 opened on Nov 12, 2019

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 (12 comments) (0 reactions) (0 assignees)Python (6,787 stars) (640 forks)batch import
help wantedtyping

Description

The type hinting for load's data argument is set to typing.Mapping which makes sense for the many=False case, but for many=True case the type of data is list, which isn't a Mapping type.

Contributor guide

Tech stack
python
Domain
backendapi
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
understanding of Python type hints
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
The issue is about the type hint for the `data` argument of the `load` method in marshmallow. The current hint uses `typing.Mapping`, which is incorrect when `many=True` since `data` is a list. Look at the `load` method definition in the source code (likely in `marshmallow/schema.py`) and consider using `typing.Union[Mapping, list]` or overloaded signatures. The discussion in the comments may provide further context on the preferred approach.