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copied!<p>Isn't this doing the thing you want?</p> <pre><code>import functools from itertools import product def the_list(): return ["foo", "bar", "baz"] def do_all(func): if hasattr(func, 'get_from'): @functools.wraps(func) def wrapper(*args, **kwargs): return tuple(func(*args) for args in product(*(lf() for lf in func.get_from))) return wrapper return func def gets_arg_from(*list_funcs): def decorator(func): func.get_from = list_funcs return func return decorator @gets_arg_from(the_list) def print_func(word): return word print print_func('foo') all = do_all(print_func) print all() </code></pre> <p><em><strong>Edit:</strong> Explanation</em></p> <p>These two code segments are identical:</p> <pre><code>@deco def func(...): some code </code></pre> <p>is the same as</p> <pre><code>func = deco(lambda ...: some code) </code></pre> <p>@something is just a syntactic sugar for the function call and anonymous function creation...</p> <p>I'll explain what happened in the next peace of code step by step:</p> <pre><code>@gets_arg_from(the_list) def print_func(word): return word </code></pre> <ol> <li><p>First Python creates an anonimous function that receives a parameter <code>word</code> and has a body that just returns this <code>word</code> (or does whatever the function body does)</p></li> <li><p>Then the function <code>get_arg_from</code> gets called and <code>the_list</code> gets passed to it as an argument</p></li> <li><p><code>get_arg_from</code> creates a <code>decorator</code> function and returnes it</p></li> <li><p>The <code>decorator</code> function returned from the <code>get_arg_from</code> is called (this is the syntactic sugar thing) passing as an argument <code>func</code> the anonimous function created in the step 1.</p></li> <li><p><code>decorator</code> just assigns the <code>list_funcs</code> tuple to the <code>get_from</code> attribute of the anonymous function and returns the anonimous function</p></li> <li><p>The return value of the <code>decorator</code> function is assigned to a variable <code>print_func</code></p></li> </ol> <p>Similar effect can be achieved with:</p> <pre><code>def __anonimous(word): return word __decorator = gets_arg_from(the_list) print_func = __decorator(__anonimous) </code></pre> <p>So basically <code>gets_arg_from</code> is not a decorator it's a function that returns a decorator.</p> <p><code>do_all</code> on the other hand <strong>is</strong> a decorator, it receives a function as an argument, and returns either the original function (if the function doesn't have the attribute <code>get_from</code>) or a <code>wrapper</code> function which replaces the original function (if it has the <code>get_from</code> attribute).</p> <p>You can find more examples <a href="http://en.wikipedia.org/wiki/Python_syntax_and_semantics#Decorators" rel="nofollow">here</a>.</p>

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