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.

Functions specific to h5py¶

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.

Parameters:

dtype_in – may be a dtype object, or anything which can be converted to a dtype, including strings like ‘<i4’ or an “int”.
logical – when 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.string_dtype()¶

Make a numpy dtype for HDF5 strings

encoding may be ‘utf-8’ or ‘ascii’.

length may be an integer for a fixed length string dtype, or None for variable length strings. String lengths for HDF5 are counted in bytes, not unicode code points.

For variable length strings, the data should be passed as Python str objects (unicode in Python 2) if the encoding is ‘utf-8’, and bytes if it is ‘ascii’. For fixed length strings, the data should be numpy fixed length bytes arrays, regardless of the encoding. Fixed length unicode data is not supported.

h5py.h5t.check_string_dtype()¶

If the dtype represents an HDF5 string, returns a string_info object.

The returned string_info object holds the encoding and the length. The encoding can only be ‘utf-8’ or ‘ascii’. The length may be None for a variable-length string, or a fixed length in bytes.

Returns None if the dtype does not represent an HDF5 string.

h5py.h5t.vlen_dtype()¶

Make a numpy dtype for an HDF5 variable-length datatype

For variable-length string dtypes, use string_dtype() instead.

h5py.h5t.check_vlen_dtype()¶

If the dtype represents an HDF5 vlen, returns the Python base class.

Returns None if the dtype does not represent an HDF5 vlen.

h5py.h5t.enum_dtype()¶

Create a NumPy representation of an HDF5 enumerated type

values_dict maps string names to integer values. basetype is an appropriate integer base dtype large enough to hold the possible options.

h5py.h5t.check_enum_dtype()¶

If the dtype represents an HDF5 enumerated type, returns the dictionary mapping string names to integer values.

Returns None if the dtype does not represent an HDF5 enumerated type.

h5py.h5t.special_dtype()¶

Create a new h5py “special” type. Only one keyword may be given.

Legal keywords are:

vlen = basetype: Base type for HDF5 variable-length datatype. This can be Python str type or instance of np.dtype. Example: special_dtype( vlen=str )
enum = (basetype, values_dict): Create a NumPy representation of an HDF5 enumerated type. Provide a 2-tuple containing an (integer) base dtype and a dict mapping string names to integer values.
ref = Reference | RegionReference: Create a NumPy representation of an HDF5 object or region reference type.

h5py.h5t.check_dtype()¶

Check a dtype for h5py special type “hint” information. Only one keyword may be given.

vlen = dtype: If the dtype represents an HDF5 vlen, returns the Python base class. Currently only builting string vlens (str) are supported. Returns None if the dtype does not represent an HDF5 vlen.
enum = dtype: If the dtype represents an HDF5 enumerated type, returns the dictionary mapping string names to integer values. Returns None if the dtype does not represent an HDF5 enumerated type.
ref = dtype: If the dtype represents an HDF5 reference type, returns the reference class (either Reference or RegionReference). Returns None if the dtype does not represent an HDF5 reference type.

Functional API¶

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. If present, tapl must be a datatype access property list.

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¶: Deserialize an HDF5 type. You can also do this with the native Python pickling machinery.

h5py.h5t.convert(TypeID src, TypeID dst, UINT n, NDARRAY buf, NDARRAY bkg=None, PropID dxpl=None)¶: Convert n contiguous elements of a buffer in-place. The array dtype is ignored. The backing buffer is optional; for conversion of compound types, a temporary copy of conversion buffer will used for backing if one is not supplied.

h5py.h5t.find(TypeID src, TypeID dst) → TUPLE or None¶

Determine if a conversion path exists from src to dst. Result is None or a tuple describing the conversion path. Currently tuple entries are:

INT need_bkg: Whether this routine requires a backing buffer.
Values are BKG_NO, BKG_TEMP and BKG_YES.

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_create_plist() → PropTCID¶: Create and return a new copy of the datatype creation property list used when this datatype was created.

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: 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:

ORDER_LE
ORDER_BE

get_pad() -> (INT lsb_pad_code, INT msb_pad_code)¶

Determine the padding type. Possible values are:

PAD_ZERO
PAD_ONE
PAD_BACKGROUND

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:

ORDER_LE
ORDER_BE

set_pad(INT lsb_pad_code, INT msb_pad_code)¶

Set the padding type. Possible values are:

PAD_ZERO
PAD_ONE
PAD_BACKGROUND

set_precision(UINT precision)¶: Set the number of significant bits (excludes padding).

class h5py.h5t.TypeIntegerID¶

Bases: 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: 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:

PAD_ZERO
PAD_ONE
PAD_BACKGROUND

get_norm() → INT normalization_code¶

Get the normalization strategy. Legal values are:

NORM_IMPLIED
NORM_MSBSET
NORM_NONE

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:

PAD_ZERO
PAD_ONE
PAD_BACKGROUND

set_norm(INT normalization_code)¶

Set the normalization strategy. Legal values are:

NORM_IMPLIED
NORM_MSBSET
NORM_NONE

Strings¶

class h5py.h5t.TypeStringID¶

Bases: 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: 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: 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: 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: 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: 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: TypeID

Non-string vlen datatypes.

class h5py.h5t.TypeBitfieldID¶

Bases: TypeID

HDF5 bitfield type

get_order() → INT order¶

Obtain the byte order of the datatype; one of:

ORDER_LE
ORDER_BE

class h5py.h5t.TypeReferenceID¶

Bases: 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¶

Reference types¶

h5py.h5t.STD_REF_OBJ¶

h5py.h5t.STD_REF_DSETREG¶

String types¶

h5py.h5t.C_S1¶: Null-terminated fixed-length string

h5py.h5t.FORTRAN_S1¶: Zero-padded fixed-length string

h5py.h5t.VARIABLE¶: Variable-length string

Python object type¶

h5py.h5t.PYTHON_OBJECT¶

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¶

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.CSET_UTF8¶

h5py.h5t.PAD_ZERO¶

h5py.h5t.PAD_ONE¶

h5py.h5t.PAD_BACKGROUND¶

h5py.h5t.BKG_NO¶

h5py.h5t.BKG_TEMP¶

h5py.h5t.BKG_YES¶

Module H5T¶

Functions specific to h5py¶

Functional API¶

Type classes¶

Atomic classes¶

Strings¶

Compound Types¶

Other types¶

Predefined Datatypes¶

Floating-point¶

Integer types¶

Reference types¶

String types¶

Python object type¶

Module constants¶

Datatype class codes¶

API Constants¶

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