Data types

This chapter describes the mapping of data types between Python and Tango.

Tango has more data types than Python which is more dynamic. The input and output values of the commands are translated according to the array below. Note that if PyTango is compiled with numpy support the numpy type will be the used for the input arguments. Also, it is recomended to use numpy arrays of the appropiate type for output arguments as well, as they tend to be much more efficient.

For scalar types (SCALAR)

Tango data type	Python 2.x type	Python 3.x type (New in PyTango 8.0)
DEV_VOID	No data	No data
DEV_BOOLEAN	bool	bool
DEV_SHORT	int	int
DEV_LONG	int	int
DEV_LONG64	long (on a 32 bits computer) int (on a 64 bits computer)	int
DEV_FLOAT	float	float
DEV_DOUBLE	float	float
DEV_USHORT	int	int
DEV_ULONG	int	int
DEV_ULONG64	long (on a 32 bits computer) int (on a 64 bits computer)	int
DEV_STRING	str	str (decoded with latin-1, aka ISO-8859-1)
DEV_ENCODED (New in PyTango 8.0)	sequence of two elements: str bytes (for any value of extract_as)	sequence of two elements: str (decoded with latin-1, aka ISO-8859-1) bytes (for any value of extract_as, except String. In this case it is str (decoded with default python encoding utf-8))

For array types (SPECTRUM/IMAGE)

Tango data type	ExtractAs	Data type (Python 2.x)	Data type (Python 3.x) (New in PyTango 8.0)
DEVVAR_CHARARRAY	Numpy	numpy.ndarray (dtype= numpy.uint8)	numpy.ndarray (dtype= numpy.uint8)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int>	list <int>
	Tuple	tuple <int>	tuple <int>
DEVVAR_SHORTARRAY or (DEV_SHORT + SPECTRUM) or (DEV_SHORT + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.uint16)	numpy.ndarray (dtype= numpy.uint16)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int>	list <int>
	Tuple	tuple <int>	tuple <int>
DEVVAR_LONGARRAY or (DEV_LONG + SPECTRUM) or (DEV_LONG + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.uint32)	numpy.ndarray (dtype= numpy.uint32)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int>	list <int>
	Tuple	tuple <int>	tuple <int>
DEVVAR_LONG64ARRAY or (DEV_LONG64 + SPECTRUM) or (DEV_LONG64 + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.uint64)	numpy.ndarray (dtype= numpy.uint64)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int (64 bits) / long (32 bits)>	list <int>
	Tuple	tuple <int (64 bits) / long (32 bits)>	tuple <int>
DEVVAR_FLOATARRAY or (DEV_FLOAT + SPECTRUM) or (DEV_FLOAT + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.float32)	numpy.ndarray (dtype= numpy.float32)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <float>	list <float>
	Tuple	tuple <float>	tuple <float>
DEVVAR_DOUBLEARRAY or (DEV_DOUBLE + SPECTRUM) or (DEV_DOUBLE + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.float64)	numpy.ndarray (dtype= numpy.float64)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <float>	list <float>
	Tuple	tuple <float>	tuple <float>
DEVVAR_USHORTARRAY or (DEV_USHORT + SPECTRUM) or (DEV_USHORT + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.uint16)	numpy.ndarray (dtype= numpy.uint16)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int>	list <int>
	Tuple	tuple <int>	tuple <int>
DEVVAR_ULONGARRAY or (DEV_ULONG + SPECTRUM) or (DEV_ULONG + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.uint32)	numpy.ndarray (dtype= numpy.uint32)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int>	list <int>
	Tuple	tuple <int>	tuple <int>
DEVVAR_ULONG64ARRAY or (DEV_ULONG64 + SPECTRUM) or (DEV_ULONG64 + IMAGE)	Numpy	numpy.ndarray (dtype= numpy.uint64)	numpy.ndarray (dtype= numpy.uint64)
	Bytes	bytes (which is in fact equal to str)	bytes
	ByteArray	bytearray	bytearray
	String	str	String str (decoded with default python encoding utf-8!!!)
	List	list <int (64 bits) / long (32 bits)>	list <int>
	Tuple	tuple <int (64 bits) / long (32 bits)>	tuple <int>
DEVVAR_STRINGARRAY or (DEV_STRING + SPECTRUM) or (DEV_STRING + IMAGE)		sequence<str>	sequence<str> (decoded with latin-1, aka ISO-8859-1)
DEV_LONGSTRINGARRAY		sequence of two elements: numpy.ndarray (dtype= numpy.int32) or sequence<int> sequence<str>	sequence of two elements: numpy.ndarray (dtype= numpy.int32) or sequence<int> sequence<str> (decoded with latin-1, aka ISO-8859-1)
DEV_DOUBLESTRINGARRAY		sequence of two elements: numpy.ndarray (dtype= numpy.float64) or sequence<int> sequence<str>	sequence of two elements: numpy.ndarray (dtype= numpy.float64) or sequence<int> sequence<str> (decoded with latin-1, aka ISO-8859-1)

For SPECTRUM and IMAGES the actual sequence object used depends on the context where the tango data is used, and the availability of numpy.

1. for properties the sequence is always a list. Example:

   >>> import PyTango
   >>> db = PyTango.Database()
   >>> s = db.get_property(["TangoSynchrotrons"])
   >>> print type(s)
   <type 'list'>
   

2. for attribute/command values

   • numpy.ndarray if PyTango was compiled with numpy support (default) and numpy is installed.
   • list otherwise