[Python-Dev] Decorators with arguments are curries!

[Phillip J. Eby]

At 10:36 PM 8/7/04 +1000, Andrew Durdin wrote:
>The first assignment to a is binding a reference to a function; the
>second is calling the function. This is a very significant difference
>in python, and I'm concerned that all the current proposed decorator
>syntaxes[*] are liable to cause confusion on this point. For example:
>
>def foo_decorator(func):
>     print "no params to this"
>     return func
>
>def bar_decorator(func, param):
>     print param
>     return func
>
>@foo_decorator
>@bar_decorator("one param here")
>def decorated_func():
>     pass
>
>Here the first decorator statement is bare, while the second one
>includes parentheses and an argument; the first one looks like a
>function reference, while the second looks like a function call.

Your example will fail, saying that bar_decorator is being called without 
enough arguments.

Decorator syntax does *not* provide currying.  You have to write something 
like this:

     def bar_decorator(param):
         def decorate(func):
             print param
             return func
         return decorate

in order for your example to work.