Module H5T
HDF5 “H5T” data-type API
This module contains the datatype identifier class TypeID, and its
subclasses which represent things like integer/float/compound identifiers.
The majority of the H5T API is presented as methods on these identifiers.
Functional API
-
h5py.h5t.py_create(OBJECT dtype_in, BOOL logical=False) → TypeID
Given a Numpy dtype object, generate a byte-for-byte memory-compatible
HDF5 datatype object. The result is guaranteed to be transient and
unlocked.
Argument dtype_in may be a dtype object, or anything which can be
converted to a dtype, including strings like ‘<i4’.
- logical
- If this flag is set, instead of returning a byte-for-byte identical
representation of the type, the function returns the closest logically
appropriate HDF5 type. For example, in the case of a “hinted” dtype
of kind “O” representing a string, it would return an HDF5 variable-
length string type.
-
h5py.h5t.create(INT classtype, UINT size) → TypeID
- Create a new HDF5 type object. Legal class values are
COMPOUND and OPAQUE. Use enum_create for enums.
-
h5py.h5t.open(ObjectID group, STRING name) → TypeID
- Open a named datatype from a file.
-
h5py.h5t.array_create(TypeID base, TUPLE dimensions) → TypeArrayID
- Create a new array datatype, using and HDF5 parent type and
dimensions given via a tuple of positive integers. “Unlimited”
dimensions are not allowed.
-
h5py.h5t.enum_create(TypeID base) → TypeID
- Create a new enumerated type based on an (integer) parent type.
-
h5py.h5t.vlen_create(TypeID base) → TypeID
Create a new variable-length datatype, using any HDF5 type as a base.
Although the Python interface can manipulate these types, there is no
provision for reading/writing vlen data.
-
h5py.h5t.decode(STRING buf) → TypeID
- Unserialize an HDF5 type. You can also do this with the native
Python pickling machinery.
Type classes
-
class h5py.h5t.TypeID
Base class for type identifiers (implements common operations)
- Hashable: If committed; in HDF5 1.8.X, also if locked
- Equality: Logical H5T comparison
-
commit(ObjectID group, STRING name, PropID lcpl=None)
- Commit this (transient) datatype to a named datatype in a file.
If present, lcpl may be a link creation property list.
-
committed() → BOOL is_comitted
- Determine if a given type object is named (T) or transient (F).
-
copy() → TypeID
- Create a copy of this type object.
-
detect_class(INT classtype) → BOOL class_is_present
- Determine if a member of the given class exists in a compound
datatype. The search is recursive.
-
dtype
- A Numpy-style dtype object representing this object.
-
encode() → STRING
- Serialize an HDF5 type. Bear in mind you can also use the
native Python pickle/unpickle machinery to do this. The
returned string may contain binary values, including NULLs.
-
equal(TypeID typeid) → BOOL
- Logical comparison between datatypes. Also called by
Python’s “==” operator.
-
get_class() → INT classcode
- Determine the datatype’s class code.
-
get_size() → INT size
- Determine the total size of a datatype, in bytes.
-
get_super() → TypeID
- Determine the parent type of an array, enumeration or vlen datatype.
-
lock()
- Lock this datatype, which makes it immutable and indestructible.
Once locked, it can’t be unlocked.
-
set_size(UINT size)
- Set the total size of the datatype, in bytes.
Atomic classes
Atomic types are integers and floats. Much of the functionality for each is
inherited from the base class TypeAtomicID.
-
class h5py.h5t.TypeAtomicID
Bases: h5py.h5t.TypeID
Base class for atomic datatypes (float or integer)
-
get_offset() → INT offset
- Get the offset of the first significant bit.
-
get_order() → INT order
Obtain the byte order of the datatype; one of:
-
get_pad() -> (INT lsb_pad_code, INT msb_pad_code)
Determine the padding type. Possible values are:
-
get_precision() → UINT precision
- Get the number of significant bits (excludes padding).
-
set_offset(UINT offset)
- Set the offset of the first significant bit.
-
set_order(INT order)
Set the byte order of the datatype; one of:
-
set_pad(INT lsb_pad_code, INT msb_pad_code)
Set the padding type. Possible values are:
-
set_precision(UINT precision)
- Set the number of significant bits (excludes padding).
-
class h5py.h5t.TypeIntegerID
Bases: h5py.h5t.TypeAtomicID
Integer atomic datatypes
-
get_sign() → INT sign
Get the “signedness” of the datatype; one of:
- SGN_NONE
- Unsigned
- SGN_2
- Signed 2’s complement
-
set_sign(INT sign)
Set the “signedness” of the datatype; one of:
- SGN_NONE
- Unsigned
- SGN_2
- Signed 2’s complement
-
class h5py.h5t.TypeFloatID
Bases: h5py.h5t.TypeAtomicID
Floating-point atomic datatypes
-
get_ebias() → UINT ebias
- Get the exponent bias.
-
get_fields() → TUPLE field_info
Get information about floating-point bit fields. See the HDF5
docs for a full description. Tuple has the following members:
- UINT spos
- UINT epos
- UINT esize
- UINT mpos
- UINT msize
-
get_inpad() → INT pad_code
Determine the internal padding strategy. Legal values are:
-
get_norm() → INT normalization_code
Get the normalization strategy. Legal values are:
-
set_ebias(UINT ebias)
- Set the exponent bias.
-
set_fields(UINT spos, UINT epos, UINT esize, UINT mpos, UINT msize)
- Set floating-point bit fields. Refer to the HDF5 docs for
argument definitions.
-
set_inpad(INT pad_code)
Set the internal padding strategy. Legal values are:
-
set_norm(INT normalization_code)
Set the normalization strategy. Legal values are:
Strings
-
class h5py.h5t.TypeStringID
Bases: h5py.h5t.TypeID
String datatypes, both fixed and vlen.
-
get_cset() → INT character_set
- Retrieve the character set used for a string.
-
get_strpad() → INT padding_type
Get the padding type. Legal values are:
- STR_NULLTERM
- NULL termination only (C style)
- STR_NULLPAD
- Pad buffer with NULLs
- STR_SPACEPAD
- Pad buffer with spaces (FORTRAN style)
-
is_variable_str() → BOOL is_variable
- Determine if the given string datatype is a variable-length string.
-
set_cset(INT character_set)
- Set the character set used for a string.
-
set_strpad(INT pad)
Set the padding type. Legal values are:
- STR_NULLTERM
- NULL termination only (C style)
- STR_NULLPAD
- Pad buffer with NULLs
- STR_SPACEPAD
- Pad buffer with spaces (FORTRAN style)
Compound Types
Traditional compound type (like NumPy record type) and enumerated types share
a base class, TypeCompositeID.
-
class h5py.h5t.TypeCompositeID
Bases: h5py.h5t.TypeID
Base class for enumerated and compound types.
-
get_member_index(STRING name) → INT index
- Determine the index of a member of a compound or enumerated datatype
identified by a string name.
-
get_member_name(INT member) → STRING name
- Determine the name of a member of a compound or enumerated type,
identified by its index (0 <= member < nmembers).
-
get_nmembers() → INT number_of_members
- Determine the number of members in a compound or enumerated type.
-
class h5py.h5t.TypeCompoundID
Bases: h5py.h5t.TypeCompositeID
Represents a compound datatype
-
get_member_class(INT member) → INT class
- Determine the datatype class of the member of a compound type,
identified by its index (0 <= member < nmembers).
-
get_member_offset(INT member) → INT offset
- Determine the offset, in bytes, of the beginning of the specified
member of a compound datatype.
-
get_member_type(INT member) → TypeID
- Create a copy of a member of a compound datatype, identified by its
index.
-
insert(STRING name, UINT offset, TypeID field)
- Add a named member datatype to a compound datatype. The parameter
offset indicates the offset from the start of the compound datatype,
in bytes.
-
pack()
- Recursively removes padding (introduced on account of e.g. compiler
alignment rules) from a compound datatype.
-
class h5py.h5t.TypeEnumID
Bases: h5py.h5t.TypeCompositeID
Represents an enumerated type
-
enum_insert(STRING name, INT/LONG value)
- Define a new member of an enumerated type. The value will be
automatically converted to the base type defined for this enum. If
the conversion results in overflow, the value will be silently
clipped.
-
enum_nameof(LONG value) → STRING name
- Determine the name associated with the given value. Due to a
limitation of the HDF5 library, this can only retrieve names up to
1023 characters in length.
-
enum_valueof(STRING name) → LONG value
- Get the value associated with an enum name.
-
get_member_value(UINT index) → LONG value
- Determine the value for the member at the given zero-based index.
Other types
-
class h5py.h5t.TypeArrayID
Bases: h5py.h5t.TypeID
Represents an array datatype
-
get_array_dims() → TUPLE dimensions
- Get the dimensions of the given array datatype as
a tuple of integers.
-
get_array_ndims() → INT rank
- Get the rank of the given array datatype.
-
class h5py.h5t.TypeOpaqueID
Bases: h5py.h5t.TypeID
Represents an opaque type
-
get_tag() → STRING tag
- Get the tag associated with an opaque datatype.
-
set_tag(STRING tag)
- Set a string describing the contents of an opaque datatype.
Limited to 256 characters.
-
class h5py.h5t.TypeVlenID
Bases: h5py.h5t.TypeID
Non-string vlen datatypes.
-
class h5py.h5t.TypeBitfieldID
Bases: h5py.h5t.TypeID
HDF5 bitfield type
-
class h5py.h5t.TypeReferenceID
Bases: h5py.h5t.TypeID
HDF5 object or region reference
Predefined Datatypes
These locked types are pre-allocated by the library.
Floating-point
-
h5py.h5t.IEEE_F32LE
-
h5py.h5t.IEEE_F32BE
-
h5py.h5t.IEEE_F64LE
-
h5py.h5t.IEEE_F64BE
Integer types
-
h5py.h5t.STD_I8LE
-
h5py.h5t.STD_I16LE
-
h5py.h5t.STD_I32LE
-
h5py.h5t.STD_I64LE
-
h5py.h5t.STD_I8BE
-
h5py.h5t.STD_I16BE
-
h5py.h5t.STD_I32BE
-
h5py.h5t.STD_I64BE
-
h5py.h5t.STD_U8LE
-
h5py.h5t.STD_U16LE
-
h5py.h5t.STD_U32LE
-
h5py.h5t.STD_U64LE
-
h5py.h5t.STD_U8BE
-
h5py.h5t.STD_U16BE
-
h5py.h5t.STD_U32BE
-
h5py.h5t.STD_U64BE
-
h5py.h5t.NATIVE_INT8
-
h5py.h5t.NATIVE_UINT8
-
h5py.h5t.NATIVE_INT16
-
h5py.h5t.NATIVE_UINT16
-
h5py.h5t.NATIVE_INT32
-
h5py.h5t.NATIVE_UINT32
-
h5py.h5t.NATIVE_INT64
-
h5py.h5t.NATIVE_UINT64
-
h5py.h5t.NATIVE_FLOAT
-
h5py.h5t.NATIVE_DOUBLE
Other types
-
h5py.h5t.STD_REF_OBJ
- Object reference
-
h5py.h5t.STD_REF_DSETREG
- Dataset region reference
-
h5py.h5t.C_S1
- Null-terminated fixed-length string
-
h5py.h5t.FORTRAN_S1
- Zero-padded fixed-length string
Module constants
Datatype class codes
-
h5py.h5t.NO_CLASS
-
h5py.h5t.INTEGER
-
h5py.h5t.FLOAT
-
h5py.h5t.TIME
-
h5py.h5t.STRING
-
h5py.h5t.BITFIELD
-
h5py.h5t.OPAQUE
-
h5py.h5t.COMPOUND
-
h5py.h5t.REFERENCE
-
h5py.h5t.ENUM
-
h5py.h5t.VLEN
-
h5py.h5t.ARRAY
API Constants
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h5py.h5t.SGN_NONE
-
h5py.h5t.SGN_2
-
h5py.h5t.ORDER_LE
-
h5py.h5t.ORDER_BE
-
h5py.h5t.ORDER_VAX
-
h5py.h5t.ORDER_NONE
-
h5py.h5t.ORDER_NATIVE
-
h5py.h5t.DIR_DEFAULT
-
h5py.h5t.DIR_ASCEND
-
h5py.h5t.DIR_DESCEND
-
h5py.h5t.STR_NULLTERM
-
h5py.h5t.STR_NULLPAD
-
h5py.h5t.STR_SPACEPAD
-
h5py.h5t.NORM_IMPLIED
-
h5py.h5t.NORM_MSBSET
-
h5py.h5t.NORM_NONE
-
h5py.h5t.CSET_ASCII
-
h5py.h5t.PAD_ZERO
-
h5py.h5t.PAD_ONE
-
h5py.h5t.PAD_BACKGROUND