NumPy: chararray() function

Last update on May 28 2022 11:21:30 (UTC/GMT +8 hours)

numpy.core.defchararray.chararray() function

The numpy.core.defchararray.chararray() function provides a convenient view on arrays of string and unicode values.

Versus a regular NumPy array of type str or unicode, this class adds the following functionality:

values automatically have whitespace removed from the end when indexed
comparison operators automatically remove whitespace from the end when comparing values
vectorized string operations are provided as methods (e.g. endswith) and infix operators (e.g. "+", "*", "%")

Syntax:

class numpy.core.defchararray.chararray(shape, itemsize=1, unicode=False, buffer=None, offset=0, strides=None, order=None)

Parameter:

Name	Description	Required / Optional
shape: tuple	Shape of the array.	Required
itemsize: int	Length of each array element, in number of characters. Default is 1.	Optional
unicode: bool	Are the array elements of type unicode (True) or string (False). Default is False.	Optional
buffer: bool	Memory address of the start of the array data. Default is None, in which case a new array is created.	Optional
offset: int	Fixed stride displacement from the beginning of an axis? Default is 0. Needs to be >=0.	Optional
strides: array_like of ints	Strides for the array (see ndarray.strides for full description). Default is None.	Optional
order: {‘C’, ‘F’}	The order in which the array data is stored in memory: 'C' -> “row major” order (the default), 'F' -> “column major” (Fortran) order.	Optional

Return value:

Example-1: numpy.chararray() function

>>> import numpy as np
>>> charary = np.chararray((4, 5))
>>> charary[:] = 'x'
>>> charary
chararray([[b'x', b'x', b'x', b'x', b'x'],
       [b'x', b'x', b'x', b'x', b'x'],
       [b'x', b'x', b'x', b'x', b'x'],
       [b'x', b'x', b'x', b'x', b'x']], 
      dtype='|S1')

Example-2: numpy.chararray() function

>>> import numpy as np
>>> charary = np.chararray(charary.shape, itemsize=7)
>>> charary[:] = 'abc' 
>>> charary
chararray([[b'abc', b'abc', b'abc', b'abc', b'abc'],
       [b'abc', b'abc', b'abc', b'abc', b'abc'],
       [b'abc', b'abc', b'abc', b'abc', b'abc'],
       [b'abc', b'abc', b'abc', b'abc', b'abc']], 
      dtype='|S7')

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