Proposal for `np.field_info`

__main__.py

import numpy as np
from field_info import field_info

dt = np.dtype([('time', [('subtime', np.int32, (30,20))], 200), ('value', np.float32, (10,2))])

assert field_info(dt)['time'].offset == 0
assert field_info(dt)['time'][1].offset == 30 * 20 * 4
# etc

field_info.py

import numpy as np

def _address_of(a):
    return a.__array_interface__['data'][0]
    
class field_info(object):
    def __init__(self, dtype):
        self._arr = np.empty((0,), dtype)

    @property
    def dtype(self):
        return np.dtype((self._arr.dtype, self._arr.shape))

    @property
    def offset(self):
        if self._arr.base is None:
            return 0
        return _address_of(self._arr) - _address_of(self._arr.base)

    @property
    def strides(self):
        return self._arr.strides[1:]

    def __getitem__(self, item):
        res = field_info.__new__(field_info)
        if isinstance(item, str):
            res._arr = self._arr[item]
            return res

        if not isinstance(item, tuple):
            item = (item,)
        res._arr = self._arr[(...,) + item]
        return res