Implementation Design

This information is not necessary to use this library, but might help contribution, and reduction of “magic”.

Libraries being used:

• openpyxl

  • Reads and writes excel files

  • Applies built in styles

  • Provides low and medium level APIs for doing excel manipulation

• beautifulsoup4

  • Parse raw HTML and provides iterables for writing out cells in excel

  • Provides access to tag level attribute and style notions

• Jinja2

  • Provides good python support for in-template flow control and variable access and templating

  • Could be replaced by any templating engine. It is only used to create raw HTML.

The writing implementation is built on few concepts:

• A “cursor” or “write head” concept, implemenated in part by htmxl.compose.write.Writer.

  • This cursor moves around a sheet, writing data and applying styles, etc.

  • This cursor keeps “recordings” of where it has been within the context of writing a “tag”.

    • This permits nested tags each applying/overriding styles from their parents

    • This also allows for the implementation of cell merging

• A htmxl.compose.write.write function

  • Knowns how to interpret each HTML tag, or delegates to a specific tag implementation function

  • Is a recursive function, allowing deeply nested tags

• Tag specific implementation functions

  • Specify where the cursor should end up after the tag is finished being written.

  • Typically calls the generic htmxl.compose.write.write function on all its child elements.

• A mix of supported inline styles and single class based styling. While the underlying excel library supports “adding” styles together, the current implementation only permits one class per element.