Development Information

The source code can be found on Github at https://github.com/frejanordsiek/hdf5storage

Package Overview

The package is currently a pure Python package; using no Cython, C/C++, or other languages.

Also, pickling is not used at all and should not be added. It is a security risk since pickled data is read through the interpreter allowing arbitrary code (which could be malicious) to be executed in the interpreter. One wants to be able to read possibly HDF5 and MAT files from untrusted sources, so pickling is avoided in this package.

The hdf5storage module contains the high level reading and writing functions, as well as the Options class for encapsulating all the various options governing how data is read and written. The high level reading and writing functions can either be given an Options object, or be given the keyword arguments that its constructur takes (they will make one from those arguments). There is also the MarshallerCollection which holds all the Marshallers (more below) and provides functions to find the appropriate Marshaller given the type of a Python object, the type string used for the ‘Python.Type’ Attribute, or the MATLAB class string (contained in the ‘MATLAB_class’ Attribute). One can give the collection additional user provided Marshallers.

The hdf5storage.exceptions module contains the special exceptions/errors required for this package not covered by existing Python exceptions/errors or those from the h5py package.

hdf5storage.Marshallers contains all the Marshallers for the different Python data types that can be read from or written to an HDF5 file. They are all automitically added to any MarshallerCollection which inspects this module and grabs all classes within it (if a class other than a Marshaller is added to this module, MarshallerCollection will need to be modified). All Marshallers need to provide the same interface as Marshallers.TypeMarshaller, which is the base class for all Marshallers in this module, and should probably be inherited from by any custom Marshallers that one would write (while it can’t marshall any types, it does have some useful built in functionality). The main Marshaller in the module is Marshallers.NumpyScalarArrayMarshaller, which can marshall most Numpy types. All the other built in Marshallers other than Marshallers.PythonDictMarshaller inherit from it since they convert their types to and from Numpy types and use the inherited functions to do the actual work with the HDF5 file.

hdf5storage.utilities contains many functions that are used throughout the pacakge, especially by the Marshallers. They include the utilities.LowLevelFile() class for low level reading and writing, which is passed to the methods of the Marshallers. Any Marshaller that needs to read or write a nested object within a Group or Python object must call its methods or other functions in the hdf5storage.utilities module. There are also several functions to get, set, and delete different kinds of HDF5 Attributes (handle things such as them already existing, not existing, etc). Then there functions to convert between different string representations, as well as encode for writing and decode after reading complex types.

TODO

There are several features that need to be added, bugs that need to be fixed, etc.

Standing Bugs

  • Structured np.ndarray with no elements, when Options.structured_numpy_ndarray_as_struct is set, are not written in a way that the dtypes for the fields can be restored when it is read back from file.

Features to Add

  • Marshallers for more Python types.

  • Marshallers to be able to read the following MATLAB types

    • Categorical Arrays

    • Tables

    • Maps

    • Time Series

    • Classes (could be hard if they don’t look like a struct in file)

    • Function Handles (wouldn’t be able run in Python, but could at least manipulate)

  • A whosmat function like the SciPy one scipy.io.whosmat().

  • A function to find and delete Datasets and Groups inside the Group Options.group_for_references that are not referenced by other Datasets in the file.