Re: User Access to the docstring of a property
Colin J. Williams schrieb: > George, > > Thanks to Dietz and yourself. > > Yes, I should have referenced the class, rather than the instance. > However, for methods, the docstring is revealed for an instance. > > Colin W. > > PS It would help if someone could explain the use of @apply in the > example Dietz gave. The documentation gives no reference to @ or to The decorator semantics are simple: @a @b(argument) def foo(): pass get translated to foo = a(b(argument)(foo)) as a decorator is nothing but function that is called with one thing, and returns something else. or the same thing, by the way. Now apply was important back then before the *args and **keywordargs shortcuts where introduced. It basically takes a function as first argument, and possibly a list and/or dict, and invokes the function with that argumens in place. So def foo(a): print a apply(foo, [10]) works as simple as foo(10) locals() is a built-in that returns a dictionary which contains all the locally known names. And property is a descriptor-creation-function, that has this signature: property(fget, fset, fdel, doc) Now we have all we need to decompose that neat property-creation-trick that doesn't pollute the class' namespace: class Foo(object): @apply def bar(): def fget(self): return self._bar doc = "bar property" return property(**locals()) What happens is this: the decoration gets translated to this: bar = apply(bar) which does simply invoke bar, and assign the result to the name bar in the class. invoking bar executes the property function, which is fed with the dictionary of the locals - coincidently named after the named arguments property takes. What I really do love about this: it doesn't pollute the namespace. Regards, Diez -- http://mail.python.org/mailman/listinfo/python-list
Re: User Access to the docstring of a property
George, Thanks to Dietz and yourself. Yes, I should have referenced the class, rather than the instance. However, for methods, the docstring is revealed for an instance. Colin W. PS It would help if someone could explain the use of @apply in the example Dietz gave. The documentation gives no reference to @ or to decorators. [EMAIL PROTECTED] wrote: > Colin J. Williams wrote: >> Is there some way that the user can access the docstring specified for a >> property? > > Do keep in mind that the docstring is not guaranteed to be available. > If > the application is run with optimization turned on, docstrings are > usually > optimized out. Docstrings are handy for reading code and maybe for > debugging, but should not be relied upon for "users", as opposed to > developers. > > -- George Young > >> Please see the example below: >> >> # propDocTest >> class A(object): >>def __init__(self, value): >> self.value= value >>def vGet(self): >> return self.value >>V= property (fget= vGet, doc="Get Value.") >> >> a= A(22) >> print a.vGet() >> print a.V >> print a.V.__doc__ # this gives the docstring for the value returned >> help(a.V) # this gives the docstring for the class/type of >> the value returned >> >> Colin W. > -- http://mail.python.org/mailman/listinfo/python-list
Re: User Access to the docstring of a property
Colin J. Williams wrote: > Is there some way that the user can access the docstring specified for a > property? Do keep in mind that the docstring is not guaranteed to be available. If the application is run with optimization turned on, docstrings are usually optimized out. Docstrings are handy for reading code and maybe for debugging, but should not be relied upon for "users", as opposed to developers. -- George Young > Please see the example below: > > # propDocTest > class A(object): >def __init__(self, value): > self.value= value >def vGet(self): > return self.value >V= property (fget= vGet, doc="Get Value.") > > a= A(22) > print a.vGet() > print a.V > print a.V.__doc__ # this gives the docstring for the value returned > help(a.V) # this gives the docstring for the class/type of > the value returned > > Colin W. -- http://mail.python.org/mailman/listinfo/python-list
Re: User Access to the docstring of a property
Colin J. Williams schrieb: > Is there some way that the user can access the docstring specified for a > property? You need to access it using the class, not an instance of it. class Foo(object): @apply def prop(): def fget(self): return 10 def fset(self, value): pass doc = "this is a docstring" return property(**locals()) f = Foo() print f.prop print Foo.prop.__doc__ print f.__class__.prop.__doc__ Diez -- http://mail.python.org/mailman/listinfo/python-list
User Access to the docstring of a property
Is there some way that the user can access the docstring specified for a property? Please see the example below: # propDocTest class A(object): def __init__(self, value): self.value= value def vGet(self): return self.value V= property (fget= vGet, doc="Get Value.") a= A(22) print a.vGet() print a.V print a.V.__doc__ # this gives the docstring for the value returned help(a.V) # this gives the docstring for the class/type of the value returned Colin W. -- http://mail.python.org/mailman/listinfo/python-list