[Python-3000] Draft pre-PEP: function annotations (original) (raw)

Talin talin at acm.org
Thu Aug 10 02:51:02 CEST 2006

Collin Winter wrote:

There is no worry that these libraries will assign semantics at random, or that a variety of libraries will appear, each with varying semantics and interpretations of what, say, a tuple of strings means. The difficulty inherent in writing annotation interpreting libraries will keep their number low and their authorship in the hands of people who, frankly, know what they're doing.

I find this assumption extremely dubious.

In pseudo-grammar, parameters now look like identifier [: expression] [= expression]. That is, type annotations always precede a parameter's default value and both type annotations and default values are optional. Just like how equal signs are used to indicate a default value, colons are used to mark annotations. All annotation expressions are evaluated at the time the function is compiled.

Only one annotation per parameter? What if I want to specify both a docstring and a type constraint?

-- Talin

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