Types and Tab Completion

Type annotations

The Piccolo codebase uses type annotations extensively. This means it has great tab completion support in tools like iPython and VSCode.

It also means it works well with type checkers like Mypy.

To learn more about how Piccolo achieves this, read this article about type annotations, and this article about descriptors.

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Troubleshooting

Here are some issues you may encounter when using Mypy, or another type checker.

id column doesn’t exist

If you don’t explicitly declare a column on your table with primary_key=True, Piccolo creates a Serial column for you called id.

In the following situation, the type checker might complains that id doesn’t exist:

await Band.select(Band.id)

You can fix this as follows:

# tables.py
from piccolo.table import Table
from piccolo.columns.column_types import Serial, Varchar


class Band(Table):
    id: Serial  # Add an annotation
    name = Varchar()