Groups, Links, and Iteration: The “H” in HDF5 - Python and HDF5 - page 55

CHAPTER 5
Groups, Links, and Iteration:
The “H” in HDF5
So far we've seen how to create Dataset objects by giving them a name in the file like
myfile["dataset1"] or myfile["dataset2"] . Unless you're one of those people who
stores all their documents on the desktop, you can probably see the flaw in this approach.
Groups are the HDF5 container object, analagous to folders in a filesystem. They can
hold datasets and other groups, allowing you to build up a hierarchical structure with
objects neatly organized in groups and subgroups.
The Root Group and Subgroups
You may have guessed by now that the File object is itself a group. In this case, it also
serves as the root group , named / , our entry point into the file.
The more general group object is h5py.Group , of which h5py.File is a subclass. Other
groups are easily created by the method create_group :
>>> f = h5py . File ( "Groups.hdf5" )
>>> subgroup = f . create_group ( "SubGroup" )
>>> subgroup
<HDF5 group "/SubGroup" (0 members)>
>>> subgroup . name
u'/SubGroup'
Of course, groups can be nested also. The create_group method exists on all Group
objects, not just File :
>>> subsubgroup = subgroup . create_group ( "AnotherGroup" )
>>> subsubgroup . name
u'/SubGroup/AnotherGroup'