[Python-Dev] ANN: PEP 335: Overloadable Boolean Operators

[Kevin Jacobs]

Phillip J. Eby wrote:

> My main concern about the PEP is that it adds overhead to *all* 
> logical operations, but the feature will only benefit code that hasn't 
> yet been written.

Actually, there are several packages that implement ugly
workarounds for exactly this issue.  So, in a sense, there
is a significant amount of code that exists that will benefit
from this feature.  Some that come to mind are my own
SQL ADT library, SQLObject, and several parser tools.

> For these reasons, I'd feel more comfortable with either a literal 
> syntax (to address algebra, SQL, etc.) or some type of special infix 
> notation to allow new operators to be defined in Python, so that it 
> isn't necessary to use prefix or method notation to perform operations 
> like these.  Neither of these solutions burdens applications that 
> don't need the feature(s).

Both of your alternatives are being used in some form and
neither is really satisfactory.  Literal representations require
complex parsers, when the Python parser is really what is
desired.  The infix notation idea is interesting, however the
operators desired are usually 'logical and' and 'logical or',
which are clearly spelled 'and' and 'or' in Python.  I see it
as a semantic limitation that Python does not allow overriding
these operators.  Adding extra indirection (i.e., extra byte
codes) _will_ affect performance, but my view is that
correctness and completeness are more important than
performance.

-Kevin