QGIS data providers are written in C++, however it is possible to simulate a data provider in Python using a memory layer and some code to interface with your data.
Why would you want to do this? Typically you should use the QGIS data providers, but here are some reasons why you may want to give it a go:
- There is no QGIS data provider
- The generic access available through OGR doesn't provide all the features you need
- You have no desire to write a provider in C++
- No one will write a C++ provider for you, for any amount of money
If you go this route you are essentially creating a bridge that connects QGIS and your data store, be it flat file, database, or some other binary format. If Python can "talk" to your data store, you can write a pseudo-provider.
To illustrate the concept, we'll create a provider for CSV files that allows you
to create a layer and have full editing capabilities using QGIS and the Python
csv module.
The provider will:
- Create a memory layer from a CSV file
- Create fields in the layer based on integer, float, or string values in the CSV
- Write changes back to the CSV file
- Require the CSV file to have an X and Y field
- Support only Point geometries
A few things about this implementation:
- It is an example, not a robust implementation
- It lacks proper error handling
- It could be extended to support other geometry types in CSV
- In its current form, it may not work for other CSV files, depending on how they are formatted (take a look at the Add Delimited Text Layer dialog in QGIS to see what I mean)
- If you want to enhance this for fun or profit---well for fun, fork the repository and give me some pull requests