[New-bugs-announce] [issue17268] Context managers written as C types no longer work in Python 2.7

[Marc-Andre Lemburg]

New submission from Marc-Andre Lemburg:

We have implemented the context manager API for connections and cursors in our mxODBC module and this works fine in Python 2.6.

In Python 2.7 we get the following error:

Traceback (most recent call last):
  File "context-manager.py", line 6, in <module>
    with db.cursor() as cursor:
AttributeError: __exit__

Here's the code snippet:

import mx.ODBC.unixODBC as ODBC
connectionString = '...'
db = ODBC.DriverConnect(connectionString)
with db.cursor() as cursor:
    print cursor

The mxODBC cursor is not an instance, it's implemented as Python type in C. It implements the tp_getattr slot, but not the tp_desc_get slot.

Looking at the apparently new API _PyObject_LookupSpecial(), this does not appear to support the tp_getattr slot and goes straight for the tp_desc_get slot.

----------
messages: 182598
nosy: lemburg
priority: normal
severity: normal
status: open
title: Context managers written as C types no longer work in Python 2.7
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue17268>
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