[Python-ideas] More useful slices (original) (raw)

Mark Lawrence breamoreboy at yahoo.co.uk
Mon Feb 2 19:38:30 CET 2015

On 02/02/2015 18:00, Skip Montanaro wrote:

On Mon, Feb 2, 2015 at 9:29 AM, Neil Girdhar <mistersheik at gmail.com> wrote:

This proposal is definitely possible, but is the only argument in its favor saving 5 characters? You already have the shorthand exactly when you most need it (indexing). As I indicated in an earlier response, there is some performance value to replacing the range function call with this (or other) syntactic sugar. While exceedingly rare, there is nothing to prevent a programmer from redefining the range builtin function or inserting a different version of range() in the local or global scopes: def myrange(*args): # completely ignore args, returning something weird... return [1, "a", None, 2] import builtin builtin.range = myrange If you have a for loop which uses range(): for i in range(27): do something interesting with i optimizers like PyPy which aim to be precisely compatible with CPython semantics must look up "range" every time it occurs and decide if it's the real builtin range function, in which case it can emit/execute machine code which is something like the C for loop: for (i=start; i<stop; i+=step) { do something interesting with i } or not, in which case it has to call whatever range is, then respond with its list of (arbtrary) Python objects. Syntactic sugar would lock down the standard behavior. Skip

You (plural) can debate this until the cows come home, but as the BDFL rejected it a couple of hours ago it strikes me as an all round waste of time and bandwidth.

-- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language.

Mark Lawrence

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