[Python-Dev] Adding a conditional expression in Py3.0 (original) (raw)

Raymond Hettinger raymond.hettinger at verizon.net
Thu Sep 29 20:28:05 CEST 2005

> It only takes about five minutes to try out a given syntax proposal on > all the fragments listed below. That short exercise provides an > excellent insight into the look and feel of each proposal in real world > code.

I did this for my favorite proposal, and ended up with the list shown further down below. I think they all looks great!

They mostly look great to me too :-)

The exceptions are the ones in pydoc which have an odd feel to them and, to my eyes, don't parse well. I can't put my finger on the issue -- it could be that any ternary operator syntax breaks down when used in series with other operators or when there are complex sub-expressions.

pydoc.py: return re.sub('^ *\n', '', rstrip(result)) if result else '' pydoc.py: anchor = (cl.name if cl else '') + '-' + name pydoc.py: lhs = '%s = ' % name if name else '' pydoc.py: contents = [doc + '\n'] if doc else [] pydoc.py: line = (name + ' = ' if name else '') + repr pydoc.py: line = (self.bold(name) + ' = ' if name else '') + repr pydoc.py: host = '127.0.0.1' if (sys.platform == 'mac') else 'localhost' pydoc.py: font = ('helvetica', 8 if sys.platform == 'win32' else 10)

There is one that looks like it could be completely mis-interpreted:

(name + ' = ' if name else '') # as written above ((name + ' = ') if name else '') # one mental interpretation (name + (' = ' if name else '')) # an incorrect interpretation

The grouping issue doesn't arise for syntaxes that start with a keyword: (if name then name + ' = ' else '') but even those suffer from unclear precedence when used with binary operations on the right: (if cond then a else b + c).

Raymond

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