Python Bindings for libcamera¶

Differences to the C++ API¶

As a rule of thumb the bindings try to follow the C++ API when possible. This chapter lists the differences.

Mostly these differences fall under two categories:

1. Differences caused by the inherent differences between C++ and Python. These differences are usually caused by the use of threads or differences in C++ vs Python memory management.
2. Differences caused by the code being work-in-progress. It’s not always trivial to create a binding in a satisfying way, and the current bindings contain simplified versions of the C++ API just to get forward. These differences are expected to eventually go away.

Coding Style¶

The C++ code for the bindings follows the libcamera coding style as much as possible. Note that the indentation does not quite follow the clang-format style, as clang-format makes a mess of the style used.

The API visible to the Python side follows the Python style as much as possible.

This means that e.g. Camera::generateConfiguration maps to Camera.generate_configuration.

CameraManager¶

The Python API provides a singleton CameraManager via CameraManager.singleton(). There is no need to start or stop the CameraManager.

Handling Completed Requests¶

The Python bindings do not expose the Camera::requestCompleted signal directly as the signal is invoked from another thread and it has real-time constraints. Instead the bindings queue the completed requests internally and use an eventfd to inform the user that there are completed requests.

The user can wait on the eventfd, and upon getting an event, use CameraManager.get_ready_requests() to clear the eventfd event and to get the completed requests.

Controls & Properties¶

The classes related to controls and properties are rather complex to implement directly in the Python bindings. There are some simplifications in the Python bindings:

• There is no ControlValue class. Python objects are automatically converted to ControlValues and vice versa.
• There is no ControlList class. A Python dict with ControlId keys and Python object values is used instead.
• There is no ControlInfoMap class. A Python dict with ControlId keys and ControlInfo values is used instead.