[Python-Dev] 3-way result of PyObject_IsTrue() considered PITA (original) (raw)

M.-A. Lemburg mal@lemburg.com
Wed, 16 Apr 2003 13:26:22 +0200

Raymond Hettinger wrote:

The docs for PyObjectIsTrue() promise that the "function always succeeds". But in reality it can return an error result if an underlying method returns an error.

The calls in ceval.c and elsewhere are cluttered and slowed by trying to handle all three possibilities. In other places (like bltinmodule.c and pyexpat.c), the result is used directly in an "if(result)" clause that ignores the possibility of an error return. Instead of fixing the docs, do you guys think there may be merit in returning False whenever explicit Truth isn't found? Favoring practicality over silent error passage?

Hmm, I've checked my sources and found that I am assuming the documented behaviour, ie. the function never fails. The Zope sources also assume this behaviour and many other extensions probably do too... (we really need a repository of available open source code for Python which makes grepping these things easier, oh well).

This would simplify the use of the function, honor the promise in the docs, and match usage in code that had not considered an error result. The function and its callers will end-up a little smaller, a little faster, and a little more consistent. Also, reasoning about truth values will be a tad simpler.

Note, similar thoughts also apply to PyObjectNot().

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