Vote on PEP 308: Ternary Operator

Clark C. Evans cce at clarkevans.com
Wed Mar 5 02:16:32 CET 2003


On Sun, Mar 02, 2003 at 09:30:03PM +0000, Dennis Reinhardt wrote:
| 308 represents too much cruft.  Most examples look good as one-liners with
| short names.  They do not look so good with longer names.  Here is an
| example:
| 
|    z_of_useful_length = 1.0 + (if abs(z_of_useful_length) < .0001:  0 else:
| z_of_useful_length)
| 
| The above long-name can be expressed in current Python in nearly the same
| number of characters as
| 
|    if abs(z_of_useful_length) < .0001:
|        z_of_useful_length = 1.0
|    else:
|        z_of_useful_length += 1.0
| 
| ... much more readable.

Agreed.  But I think you are throwing out the baby with the
bathwater here.  What is useful about the terinary operator
is that for assignments it is clear that the lhs is uniform.

   z_of_useful_length =   select abs(z_of_useful_length)
                            case < .0001: 1.0
                            else: 1.0 + z_of_useful_length

In this case it is clear that you are making an assignment
with two choices.  This syntax also extends nicely to 
facilitate more than one case.

Clark





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