Developer’s Guide

Trajectory reader implementation

To implement a trajectory reader, first keep in mind that a garnett trajectory is simply a sequence of frames. This means that a trajectory reader needs to generate individual instances of frames.

To implement a new reader:

1. Provide a minimal sample for your format.
2. Create a new module in garnett with the name yourformatreader.py.
3. Specialize a frame class for your format called YourFormatFrame.
4. Implement the read() method for your frame, it should return an instance of garnett.trajectory._RawFrameData.

class YourFormatFrame(trajectory.Frame):

    def read():
        """Read the frame data from the stream.

        :returns: :class:`.trajectory._RawFrameData`
        """

5. Define a class YourFormatReader, where the constructor may take optional arguments for your reader.
6. The YourFormatReader class needs to implement a read() method.

class YourFormatReader(object):

    def read(stream):
        """Read the trajectory from stream.

        .. code::

            # pseudo-example
            frames = list(self.scan(stream))
            return trajectory.Trajectory(frames)

        :stream: A file-like object.
        :returns: :class:`.trajectory.Trajectory`
        """

7. Add your reader class to the __all__ directive in the garnett/reader.py module.
8. Provide a unit test for your reader, that reads a sample and generates a trajectory object accordingly.

For an example, please see the GSDHOOMDFileReader implementation.