[Python-ideas] 'where' statement in Python? (original) (raw)

Carl M. Johnson cmjohnson.mailinglist at gmail.com
Thu Jul 22 06:07:19 CEST 2010

There have been questions about whether there are any cases of the given/where/let/whatever solving problems that would otherwise be cumbersome to solve. I think it could help get around certain for-loop gotchas:

funcs = [] for i in range(5): ... def f(): ... print("#", i) ... funcs.append(f) ... [func() for func in funcs]

4

4

4

4

4

[None, None, None, None, None]

D’oh! (This can be a real world problem if you have a list of methods you want to decorate inside a class.)

One current workaround:

funcs = [] for i in range(5): ... def _(): ... n = i ... def f(): ... print("#", n) ... funcs.append(f) ... _() ... [func() for func in funcs]

0

1

2

3

4

[None, None, None, None, None]

Not pretty, but it works.

In let format (I’m leaning toward the format “let [VAR = | return | yield] EXPRESSION where: BLOCK”):

funcs = [] for i in range(5): let funcs.append(f) where: n = i def f(): print("#", n)

[func() for func in funcs]

Still a little awkward, but not as bad, IMHO.

-- Carl Johnson

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