[Python-Dev] Avoiding error from repr() of recursive dictview (original) (raw)

Ben North ben at redfrontdoor.org
Mon Jul 22 23:44:28 CEST 2013

Hi,

A friend of mine, Ruadhan O'Flanagan, came across a bug which turned out to be the one noted in [http://bugs.python.org/issue18019], i.e.:

d={} d[42]=d.viewvalues() d

This issue has been fixed in hg; the behaviour now is that a RuntimeError is produced for a recursive dictionary view:

d={} d[42]=d.viewvalues() d # (output line-broken:) {42: Traceback (most recent call last): File "", line 1, in RuntimeError: maximum recursion depth exceeded while getting the repr of a list

Before finding this, though, I'd investigated and made a patch which produces a similar "..." output to a recursive dictionary. Reworking against current 2.7, the behaviour would be:

x={} x[42]=x x # existing behaviour for dictionaries: {42: {...}}

d={} d[42]=d.viewvalues() d # new behaviour: {42: dict_values([...])} d[43]=d.viewitems() d # (output line-broken:) {42: dict_values([..., dict_items([(42, ...), (43, ...)])]), 43: dict_items([(42, dict_values([..., ...])), (43, ...)])}

Attached is the patch, against current 2.7 branch. If there is interest in applying this, I will create a proper patch (changelog entry, fix to Lib/test/test_dictviews.py, etc.).

Thanks,

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