Paddy wrote: > On Jan 30, 9:51 pm, "Colin J. Williams" <[EMAIL PROTECTED]> wrote: >> It would be helpful if the rules of the game were spelled out more clearly. >> >> The conditional expression is defined as X if C else Y. >> We don't know the precedence of the "if" operator. From the little test >> below, it seem to have a lower precedence than "or". >> >> Thus, it is desirable for the user to put the conditional expression in >> parentheses. >> >> Colin W. >> >> # condExpr.py >> # PEP 308 defines a conditional expression as X if C else Y >> # but we don't know exactly what X is supposed to be. >> # It doesn't seem to be spelled out in the syntax. >> >> def main(): >> names= ['abc', 'def', '_ghi', 'jkl', '_mno', 'pqrs'] >> res= '' >> for w in names: >> res= res + w if w[0] != '_' else '' >> z= 1 >> print 'res1:', res >> >> res= '' >> for w in names: >> res= res + (w if w[0] != '_' else '') >> z= 1 >> print 'res2:', res >> >> if __name__ == '__main__': >> main() >> >> Result: >> [Dbg]>>> >> res1: pqrs >> res2: abcdefjklpqrs > > But to give them credit though, in Whats new in Python 2.5: PEP 308, > they do mention that as a matter of style you should parenthesise the > if-expression, and the example given consistes of just a simple > assignment of the if-expr to a name. > - Paddy. > Yes, I agree. The ternary operator is a step forward.
I was trying to make the point that the parentheses are necessary if X is more than a simple value. It's a pity that one finds this out by experiment rather than definition. Colin W. -- http://mail.python.org/mailman/listinfo/python-list