def is_idx(index):

    if type(index) in six.integer_types:
        return True
    elif hasattr(index, "__index__"):  # Only works on Python 2.5 (PEP 357)
        # Exclude the array([idx]) as working as an index.  Fixes #303.
        if (hasattr(index, "shape") and index.shape != ()):
            return False
        try:
            index.__index__()
            if isinstance(index, bool):
                warnings.warn(
                    'using a boolean instead of an integer will result in an '
                    'error in the future', DeprecationWarning, stacklevel=2)
            return True
        except TypeError:
            return False
    elif isinstance(index, numpy.integer):
        return True
    # For Python 2.4 one should test 0-dim and 1-dim, 1-elem arrays as well
    elif (isinstance(index, numpy.ndarray) and (index.shape == ()) and
          index.dtype.str[1] == 'i'):
        return True

    return False
Checks if an object can work as an index or not.
dataset/ETHPy150Open PyTables/PyTables/tables/utils.py/is_idx