Module H5G

Low-level HDF5 “H5G” group interface.

Functional API loc, STRING name) GroupID

Open an existing HDF5 group, attached to some other group.

h5py.h5g.create(ObjectID loc, STRING name or None, PropLCID lcpl=None, PropGCID gcpl=None) GroupID

Create a new group, under a given parent group. If name is None, an anonymous group will be created in the file.

h5py.h5g.iterate(GroupID loc, CALLABLE func, UINT startidx=0, **kwds) Return value from func

Iterate a callable (function, method or callable object) over the members of a group. Your callable should have the signature:

func(STRING name) => Result

Returning None continues iteration; returning anything else aborts iteration and returns that value. Keywords:

STRING obj_name (“.”)

Iterate over this subgroup instead

h5py.h5g.get_objinfo(ObjectID obj, STRING name='.', BOOL follow_link=True) GroupStat object

Obtain information about a named object. If “name” is provided, “obj” is taken to be a GroupID object containing the target. The return value is a GroupStat object; see that class’s docstring for a description of its attributes.

If follow_link is True (default) and the object is a symbolic link, the information returned describes its target. Otherwise the information describes the link itself.

Info objects

class h5py.h5g.GroupStat

Represents the H5G_stat_t structure containing group member info.

Fields (read-only):

  • fileno: 2-tuple uniquely identifying the current file

  • objno: 2-tuple uniquely identifying this object

  • nlink: Number of hard links to this object

  • mtime: Modification time of this object

  • linklen: Length of the symbolic link name, or 0 if not a link.

“Uniquely identifying” means unique among currently open files, not universally unique.

  • Hashable: Yes

  • Equality: Yes

Group objects

class h5py.h5g.GroupID

Represents an HDF5 group identifier

Python extensions:


Test for group member (“if name in grpid”)


Get an iterator over member names


Number of members in this group; len(grpid) = N

The attribute “links” contains a proxy object providing access to the H5L family of routines. See the docs for h5py.h5l.LinkProxy for more information.

  • Hashable: Yes, unless anonymous

  • Equality: True HDF5 identity unless anonymous

get_comment(STRING name) STRING comment

Retrieve the comment for a group member.

get_create_plist() PropGCID

Retrieve a copy of the group creation property list used to create this group.

get_linkval(STRING name) STRING link_value

Retrieve the value (target name) of a symbolic link. Limited to 2048 characters on Windows.

get_num_objs() INT number_of_objects

Get the number of objects directly attached to a given group.

get_objname_by_idx(INT idx) STRING

Get the name of a group member given its zero-based index.

get_objtype_by_idx(INT idx) INT object_type_code

Get the type of an object attached to a group, given its zero-based index. Possible return values are:

Create a new hard or soft link. current_name identifies the link target (object the link will point to). The new link is identified by new_name and (optionally) another group “remote”.

Link types are:


Hard link to existing object (default)


Symbolic link; link target need not exist.

move(STRING current_name, STRING new_name, GroupID remote=None)

Relink an object. current_name identifies the object. new_name and (optionally) another group “remote” determine where it should be moved.

set_comment(STRING name, STRING comment)

Set the comment on a group member.

Remove a link to an object from this group.

Module constants

Object type codes

Symbolic link


HDF5 group


HDF5 dataset


Named (file-resident) datatype