Paginator class

Provide mechanisms to implement a custom paginating SQLAlchemy Query.

For usage example, see the following test modules:

  • ./tests/test_11_paginator_postgresql.py

  • ./tests/test_12_paginator_mysql.py

class bh_database.paginator.Paginator(query: Query, page: int, per_page: int)

Bases: object

Provides mechanisms to implement a custom paginating SQLAlchemy Query.

It receives three (3) main inputs: a fully loaded SQLAlchemy Query, a page number and a number of records per page, it calculates and prepares paginated data. And returns its own instance. Callers can then access instance properties to prepare final data.

Parameters:

  • query – sqlalchemy.orm.Query, which is opened, and data are ready to be fetched.

  • page (int) – the page number to retrieve data for.

  • per_page (int) – how many records to retrieve for each page.

execute()

Carry out the paginating operation.

Calculating values for properties, retrieve target data rows.

property page: int

Read only property. The requested page number.

If the originally requested page number is greater than the calculated total_pages, then the value of this property is set to total_pages.

property per_page: int

Read only property. The requested number of records per page.

property total_records: int

Read only property. The total number of records retrieved.

property total_pages: int

Read only property. The total number of pages.

Its value is calculated page on total_records and per_page properties.

property offset: int

Read only property. It is 0-based.

From which row number to retrieve data for the requested page.

property limit: int

Read only property. The requested number of records per page.

Its value is basically per_page, but if total_pages is 0, then it is set to 0 also.

property items: list

Read only property.

This is essentially the paginated data for the requested page. It is a list of rows from offset to limit, inclusively.

Rows are copied or rather referenced from Query directly, there is no additional process performed on the rows when copied to this list.

property has_next: bool

Read only property.

True if there is a next page. False otherwise.

property has_prev: bool

Read only property.

True if there is a previous page. False otherwise.