numpy.recarray

class numpy.recarray

Construct an ndarray that allows field access using attributes.

Arrays may have a data-types containing fields, analagous to columns in a spread sheet. An example is [(x, int), (y, float)], where each entry in the array is a pair of (int, float). Normally, these attributes are accessed using dictionary lookups such as arr['x'] and arr['y']. Record arrays allow the fields to be accessed as members of the array, using arr.x and arr.y.

Parameters:

shape : tuple

Shape of output array.

dtype : data-type, optional

The desired data-type. By default, the data-type is determined from formats, names, titles, aligned and byteorder.

formats : list of data-types, optional

A list containing the data-types for the different columns, e.g. ['i4', 'f8', 'i4']. formats does not support the new convention of using types directly, i.e. (int, float, int). Note that formats must be a list, not a tuple. Given that formats is somewhat limited, we recommend specifying dtype instead.

names : tuple of strings, optional

The name of each column, e.g. ('x', 'y', 'z').

buf : buffer, optional

By default, a new array is created of the given shape and data-type. If buf is specified and is an object exposing the buffer interface, the array will use the memory from the existing buffer. In this case, the offset and strides keywords are available.

Returns:

rec : recarray

Empty array of the given shape and type.

See also

rec.fromrecords

Construct a record array from data.

record

fundamental data-type for recarray

format_parser

determine a data-type from formats, names, titles

Notes

This constructor can be compared to empty: it creates a new record array but does not fill it with data. To create a reccord array from data, use one of the following methods:

1. Create a standard ndarray and convert it to a record array, using arr.view(np.recarray)
2. Use the buf keyword.
3. Use np.rec.fromrecords.

Examples

Create an array with two fields, x and y:

>>> x = np.array([(1.0, 2), (3.0, 4)], dtype=[('x', float), ('y', int)])
>>> x
array([(1.0, 2), (3.0, 4)],
      dtype=[('x', '<f8'), ('y', '<i4')])

>>> x['x']
array([ 1.,  3.])

View the array as a record array:

>>> x = x.view(np.recarray)

>>> x.x
array([ 1.,  3.])

>>> x.y
array([2, 4])

Create a new, empty record array:

>>> np.recarray((2,),
... dtype=[('x', int), ('y', float), ('z', int)]) #doctest: +SKIP
rec.array([(-1073741821, 1.2249118382103472e-301, 24547520),
       (3471280, 1.2134086255804012e-316, 0)],
      dtype=[('x', '<i4'), ('y', '<f8'), ('z', '<i4')])