[Python-Dev] Shortcut Notation for Chaining Method Calls (original) (raw)
Michael O'Keefe mokeefe at okeefecreations.com
Sat Feb 3 18:36:10 CET 2007
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I had an idea on some new functionality I'd like to see offered in the python object class. I did some searching on the list but I wouldn't doubt that someone has proposed something like this before as chaining method calls seems like something folks would want to do.
Specifically, I'd like to see a built-in shorthand to allow me to chain method calls even when a method call does not explicity return a reference to the instance of the object (self).
I have an example below. In this example, someFunc represents the current way of dealing with calling methods that modify an object's state with no return value (if you found yourself doing this a lot, you might just write a wrapper function).
The function explicitReturn shows how things might go if python implicitly returned self when no other return value was specified (similar to Ruby). I'm not proposing this, but have included it for completeness.
The final two functions give some options for what I'm proposing as a shorthand (ideally included in class object but used in a subclass of class list in this example). The first of the two functions, newFunc01, defines the method "_". I'm not crazy about this because it's not very descriptive but it is the shortest way I could think of.
The second possible shorthand is in, newFunc02, which defines the method "self_". I didn't want the method to be too long but my intent was "apply the given method and return self". I used the trailing underscore so as not to confuse with the self instance variable.
I'm sure there are other ways to do this as well but what do people think? Has something like this come up before?
def someFunc(): a = list([8,9,7,1]) a.sort() a.reverse() a.pop(0) return a
def explicitReturn(): a = ExplicitReturnList([8,9,7,1]).sort().reverse() a.pop(0) return a
def newFunc01(): return NewList([8,9,7,1]).('sort').('reverse')._('pop',0)
def newFunc02(): return NewList([8,9,7,1]).self_('sort').self_('reverse').self_('pop',0)
class NewList(list): def init(self,*args,**kwargs): list.init(self,*args,**kwargs) def (self,methodName,*args,**kwargs): method = getattr(self,methodName) method(*args,**kwargs) return self def self(self,methodName,*args,**kwargs): method = getattr(self,methodName) method(*args,**kwargs) return self
class ExplicitReturnList(list): def init(self,*args,**kwargs): list.init(self,*args,**kwargs) def sort(self): super(ExplicitReturnList,self).sort() return self def reverse(self): super(ExplicitReturnList,self).reverse() return self
print someFunc() # returns [8, 7, 1] print explicitReturn() # returns [8, 7, 1] print newFunc01() # returns [8, 7, 1] print newFunc02() # returns [8, 7, 1]
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