Graphics Reference
In-Depth Information
About the QGIS Python APIs
The QGIS system itself is written in C++, and has its own set of APIs that are also written
in C++. The Python APIs are implemented as wrappers around these C++ APIs. For ex-
ample, there is a Python class named
QgisInterface
that acts as a wrapper around a
C++ class of the same name. All the methods, class variables, and the like that are imple-
mented by the C++ version of
QgisInterface
are made available through the Python
wrapper.
What this means is that when you access the Python QGIS APIs, you aren't accessing the
API directly. Instead, the wrapper connects your code to the underlying C++ objects and
methods, as follows:
Fortunately, in most cases, the QGIS Python wrappers simply hide away the complexity of
the underlying C++ code, so the PyQGIS libraries work as you would expect them to.
There are some gotchas, however, and we will cover these as they come up.
