[ARROW-2423] [Python] PyArrow datatypes raise ValueError on equality checks against non-PyArrow objects

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.9.0
• Fix Version/s: 0.10.0
• Component/s: Python
• Labels: beginner pull-request-available
• Environment: Mac OS High Sierra ; PyArrow 0.9.0 (py36_1) ; Python 3.6.3
• External issue URL: https://github.com/apache/arrow/issues/18519
• Assignee: Krisztian Szucs
• Reporter: Dave Challis
• Created: 09/Apr/18 13:37
• Updated: 11/Jan/23 07:20
• Resolved: 19/Apr/18 14:23

Description

Checking a PyArrow datatype object for equality with non-PyArrow datatypes causes a `ValueError` to be raised, rather than either returning a True/False value, or returning NotImplemented if the comparison isn't implemented.

E.g. attempting to call:

import pyarrow
pyarrow.int32() == 'foo'

results in:

Traceback (most recent call last):
  File "types.pxi", line 1221, in pyarrow.lib.type_for_alias
KeyError: 'foo'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "t.py", line 2, in <module>
    pyarrow.int32() == 'foo'
  File "types.pxi", line 90, in pyarrow.lib.DataType.__richcmp__
  File "types.pxi", line 113, in pyarrow.lib.DataType.equals
  File "types.pxi", line 1223, in pyarrow.lib.type_for_alias
ValueError: No type alias for foo

The expected outcome for the above would be for the comparison to return `False`, as that's the general behaviour for comparisons between objects of different types (e.g. `1 == 'foo'` or `object() == 12.4` both return `False`).

Issue Links

• links to: GitHub Pull Request #1914