[Python-ideas] Sorry for yet another self discussion
steve at pearwood.info
Thu May 10 18:33:48 EDT 2018
On Thu, May 10, 2018 at 07:58:12PM +0000, stefano wrote:
> The disturbing part of the "self parameter" is the asymmetry of the
> definition and the call.
Why is that disturbing? There is always some asymmetry between
*defining* a function and *calling* a function.
def function(named parameter list):
We don't repeat the keyword "def" or the colon in the call, and we
obviously don't repeat the body of the block. We typically call the
function with either positional arguments, or only a *subset* of the
keyword arguments, relying on defaults to fill in the rest. The
arguments we provide will often be expressions, sometimes complex
expressions, not just simple names. Even if they are simple names, they
rarely match the parameter name:
function(spam, eggs, cheese=None, aardvark=True)
function((foo + bar) or baz, foobar)
So whatever symmetry there is, it isn't much.
> So I was thinking: why not do define the methods
> like: "def self.whatevermethod(par1, par2, etc)" instead of "def
> whatevermethod(self, par1, par2, etc)"?
"Why not ..." is the wrong question. Adding new features to the
language, or new syntax, is not Default Allow ("add the feature, unless
there is a compelling reason not to"). There has to be a good,
positive reason for adding the feature, not merely a lack of reason
What does this feature buy us? Not much.
It doesn't add any new expressiveness to the language. It doesn't let
the language do anything that couldn't be done before.
What it does do is add complexity to the syntax, there now being two
ways to specify the first parameter:
def method(self, arg)
both of which need to be supported, which means more complexity to the
language, more documentation needed, more for people to learn, more for
tutorials to have to cover, more tests needed, etc, and all those costs
don't actually gain us any significant advantage for the code we write.
And what happens with classmethods and staticmethods, or those people
who for whatever reason refuse to use the name "self" for the first
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