BUG: `numpy.str_` and `numpy.bytes_` scalars do not support `[()]` indexing despite having `shape == ()`

Describe the issue:

numpy.str_ and numpy.bytes_ are 0-dimensional numpy scalars (shape == (), ndim == 0), yet indexing them with [()] (empty tuple, which is the standard way to extract the value from a 0-d array/scalar) raises a TypeError. This is inconsistent with all other numpy scalar types where scalar[()] works correctly.

The issue appears to be that Python's str.__getitem__ / bytes.__getitem__ takes priority over numpy's scalar indexing protocol, interpreting () as a tuple index into the string/bytes sequence rather than as a 0-d array index.

Expected behavior

numpy.str_('hello')[()] should return 'hello' (the Python str value), consistent with how numpy.int64(5)[()] returns 5.

Since numpy.str_ reports shape == () and ndim == 0, it should support the standard 0-d indexing protocol that all other numpy scalars support. Code that generically extracts values from 0-d numpy scalars via val[()] breaks specifically for string and bytes scalars.

Workaround

Use .item() instead of [()]:

np.str_('hello').item()   # => 'hello'  (works)
np.bytes_(b'hello').item()  # => b'hello'  (works)

.item() works consistently across all numpy scalar types.

Reproduce the code example:

import numpy as np

# All other numpy scalar types support [()] indexing:
assert np.int64(5)[()] == 5
assert np.float64(3.14)[()] == 3.14
assert np.bool_(True)[()] == True
assert np.complex128(1+2j)[()] == (1+2j)

# numpy.str_ and numpy.bytes_ do NOT, despite having shape == ():
s = np.str_('hello')
print(f"type: {type(s)}, shape: {s.shape}, ndim: {s.ndim}")  # shape=(), ndim=0

s[()]  # TypeError: string indices must be integers, not 'tuple'

b = np.bytes_(b'hello')
print(f"type: {type(b)}, shape: {b.shape}, ndim: {b.ndim}")  # shape=(), ndim=0

b[()]  # TypeError: byte indices must be integers or slices, not tuple

Error message:

TypeError: string indices must be integers, not 'tuple'



TypeError: byte indices must be integers or slices, not tuple

Python and NumPy Versions:

numpy version: 2.2.6
Python 3.11.2 (main, Aug 26 2024, 07:20:54) [GCC 12.2.0]

Runtime Environment:

No response

How does this issue affect you or how did you find it:

No response

Run the provided reproduction for numpy.str_ and numpy.bytes_ and compare it with the working scalar examples using [()]. Start by tracing the scalar indexing path around the Python string/bytes indexing behavior and NumPy's 0-dimensional scalar protocol. Done means both string and bytes scalars accept [()] and return their Python values without breaking existing indexing behavior.