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✏️ Editing: defchararray.py

"""
This module contains a set of functions for vectorized string
operations and methods.

.. note::
   The `chararray` class exists for backwards compatibility with
   Numarray, it is not recommended for new development. Starting from numpy
   1.4, if one needs arrays of strings, it is recommended to use arrays of
   `dtype` `object_`, `bytes_` or `str_`, and use the free functions
   in the `numpy.char` module for fast vectorized string operations.

Some methods will only be available if the corresponding string method is
available in your version of Python.

The preferred alias for `defchararray` is `numpy.char`.

"""
import functools

from .._utils import set_module
from .numerictypes import (
    bytes_, str_, integer, int_, object_, bool_, character)
from .numeric import ndarray, compare_chararrays
from .numeric import array as narray
from numpy.core.multiarray import _vec_string
from numpy.core import overrides
from numpy.compat import asbytes
import numpy

__all__ = [
    'equal', 'not_equal', 'greater_equal', 'less_equal',
    'greater', 'less', 'str_len', 'add', 'multiply', 'mod', 'capitalize',
    'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs',
    'find', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace',
    'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'partition',
    'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit',
    'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase',
    'title', 'translate', 'upper', 'zfill', 'isnumeric', 'isdecimal',
    'array', 'asarray'
    ]

_globalvar = 0

array_function_dispatch = functools.partial(
    overrides.array_function_dispatch, module='numpy.char')

def _is_unicode(arr):
    """Returns True if arr is a string or a string array with a dtype that
    represents a unicode string, otherwise returns False.

"""
    if (isinstance(arr, str) or
            issubclass(numpy.asarray(arr).dtype.type, str)):
        return True
    return False

def _to_bytes_or_str_array(result, output_dtype_like=None):
    """
    Helper function to cast a result back into an array
    with the appropriate dtype if an object array must be used
    as an intermediary.
    """
    ret = numpy.asarray(result.tolist())
    dtype = getattr(output_dtype_like, 'dtype', None)
    if dtype is not None:
        return ret.astype(type(dtype)(_get_num_chars(ret)), copy=False)
    return ret

def _clean_args(*args):
    """
    Helper function for delegating arguments to Python string
    functions.

Many of the Python string operations that have optional arguments
    do not use 'None' to indicate a default value.  In these cases,
    we need to remove all None arguments, and those following them.
    """
    newargs = []
    for chk in args:
        if chk is None:
            break
        newargs.append(chk)
    return newargs

def _get_num_chars(a):
    """
    Helper function that returns the number of characters per field in
    a string or unicode array.  This is to abstract out the fact that
    for a unicode array this is itemsize / 4.
    """
    if issubclass(a.dtype.type, str_):
        return a.itemsize // 4
    return a.itemsize

def _binary_op_dispatcher(x1, x2):
    return (x1, x2)

@array_function_dispatch(_binary_op_dispatcher)
def equal(x1, x2):
    """
    Return (x1 == x2) element-wise.

Unlike `numpy.equal`, this comparison is performed by first
    stripping whitespace characters from the end of the string.  This
    behavior is provided for backward-compatibility with numarray.