On 2021-09-29 10:11, Dominik Vilsmeier wrote:
Lambda functions that have a single parameter are a common thing, e.g. for "key" functions:
`sorted(items, key=lambda x: x['key'])`. For these cases however, the rather long word
"lambda" together with the repetition of the parameter name, results in more overhead than
actual content (the `x['key']`) and thus makes it more difficult to read. This is also a difficulty
for `map` and `filter` for example where there's lots of visual overhead when using a lambda function
and hence it's difficult to read: `filter(lambda x: x > 0, items)` or `map(lambda x: f'{x:.3f}',
items)`.
Hence the proposal is to add a new syntax via the new token `?`. For the
examples above:
* `sorted(items, key=?['key'])`
* `filter(? > 0, items)`
* `map(f'{?:.3f}', items)`
The rules are simple: whenever the token `?` is encountered as part of an
expression (at a position where a name/identifier would be legal), the
expression is replaced by a lambda function with a single parameter which has
that expression as a return value, where any instances of `?` are replaced by
the name of that single parameter. For example:
* `?['key']` translates to `lambda x: x['key']`
* `? > 0` translates to `lambda x: x > 0`
* `f'{?:.3f}'` translates to `lambda x: f'{x:.3f}'`
* `?*?` translates to `lambda x: x*x`
[snip]
I'd prefer something like "x -> x" "x => x" as an equivalent to "lambda
x: x":
sorted(items, key=i -> i['key'])
The advantage of using '->' is that it already exists.
This has all been suggested before.
There have also the suggestions of adding a None-coalesce operator '??',
plus None-coalesce subscripting with '?[...]', etc, which would be
Python's equivalent of the null-coalesce operator of some other languages.
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