[Python-ideas] except expression

[Oscar Benjamin]

On 19 February 2014 07:06, Chris Angelico <rosuav at gmail.com> wrote:
> On Wed, Feb 19, 2014 at 5:10 PM, Chris Angelico <rosuav at gmail.com> wrote:
>
> Current PEP draft:
>
> https://raw2.github.com/Rosuav/ExceptExpr/master/pep-0463.txt

It looks good to me.

I think I most often use the ternary if/else as part of a larger
expression such as a dict display. I can imagine that the same would
apply here and it might be good to add an example of this.

I don't know how common a pattern it is in other people's code but
something like:

header = {
    'param1': foo,
    'param2': bar,
    ...
}

try:
    header['paramN'] = load_from_file(baz, spam)
except OSError:
    header['paramN'] = ''

In this case your proposed syntax would make it possible to write the
whole thing as a single expression. Without the syntax you'd probably
need to write an additional function to get the same effect:

def load_from_file_default_None(baz, spam):
    try:
        return load_from_file(baz, spam)
    except OSError:
        return None


Oscar