Source code for astropy.utils.metadata.utils

# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""This module contains helper functions handling metadata."""

import numpy as np

from astropy.utils.misc import dtype_bytes_or_chars

from .exceptions import MergeConflictError

__all__ = ["common_dtype"]

def dtype(arr):
    return getattr(arr, "dtype", np.dtype("O"))

[docs] def common_dtype(arrs): """ Use numpy to find the common dtype for a list of ndarrays. Only allow arrays within the following fundamental numpy data types: ``np.bool_``, ``np.object_``, ``np.number``, ``np.character``, ``np.void`` Parameters ---------- arrs : list of ndarray Arrays for which to find the common dtype Returns ------- dtype_str : str String representation of dytpe (dtype ``str`` attribute) """ np_types = (np.bool_, np.object_, np.number, np.character, np.void) uniq_types = { tuple(issubclass(dtype(arr).type, np_type) for np_type in np_types) for arr in arrs } if len(uniq_types) > 1: # Embed into the exception the actual list of incompatible types. incompat_types = [dtype(arr).name for arr in arrs] tme = MergeConflictError(f"Arrays have incompatible types {incompat_types}") tme._incompat_types = incompat_types raise tme arrs = [np.empty(1, dtype=dtype(arr)) for arr in arrs] # For string-type arrays need to explicitly fill in non-zero # values or the final arr_common = .. step is unpredictable. for i, arr in enumerate(arrs): if arr.dtype.kind in ("S", "U"): arrs[i] = [ ("0" if arr.dtype.kind == "U" else b"0") * dtype_bytes_or_chars(arr.dtype) ] arr_common = np.array([arr[0] for arr in arrs]) return ( arr_common.dtype.str if arr_common.dtype.names is None else arr_common.dtype.descr )