Verbose and flexible args and kwargs syntax

[Eelco Hoogendoorn]

Throwing an idea for a PEP out there:

It strikes me that the def func(*args, **kwargs) syntax is rather
unpytonic. It certainly did not have that 'for line in file' pythonic
obviousness for me as a beginner. Plus, asterikses are impossible to
google for, so finding out what exactly they do more or less forces you
to write a forum post about it.

A more readable form occurred to me, which also happens to be more
flexible, and which I think is fully compatible with the syntax of the
language:

def func(parg, list(args), dict(kwargs))

Perhaps this is considered abuse of notation; dict(kwargs) already has a
meaning rather different from the one we try to give it here; but then
again the context (being inside a function definition) is unique and
easily recognizable.

An added advantage would be the possibility of using subclasses of dict
and list as well; imagine how much more beautiful a lot of code would be
if one could say

def func(attrdict(kwargs))

Problems im still wrestling with: the same syntax could not be used when
calling a function; that lack of symmetry would make things more
confusing, not less.

Thoughts?

 

[Steven D'Aprano]

Throwing an idea for a PEP out there:

It strikes me that the def func(*args, **kwargs) syntax is rather
unpytonic. It certainly did not have that 'for line in file' pythonic
obviousness for me as a beginner. Plus, asterikses are impossible to
google for, so finding out what exactly they do more or less forces you
to write a forum post about it.

No more so than any other form of punctuation. Plus and minus + - may be
so common that just about everyone knows it, but how about | == @ % and
even . (dot)? None of these things will be obvious to newbies who have
never programmed before. Oh well.

Some things you just have to learn.

As for impossibility of googling for asterisks, it might help if you
spell it correctly <wink>

http://duckduckgo.com/?q=python+asterisk

Fourth hit says:

*vargs puts all left-over non-keyword arguments into a
tuple called vargs. **kargs puts all left-over keyword
arguments into a dictionary called kargs.

Even better, this works amazingly well:

http://duckduckgo.com/?q=python+*

Or you can Read The Fine Manual, which has a section for special symbols:

http://docs.python.org/genindex-Symbols.html

which is moderately easy to discover from the main page: Main page =>
Documentation => Browse Current Documentation => General Index =>
Symbols. Not ideal, but not too bad.

A more readable form occurred to me, which also happens to be more
flexible, and which I think is fully compatible with the syntax of the
language:

def func(parg, list(args), dict(kwargs))

Perhaps this is considered abuse of notation; dict(kwargs) already has a
meaning rather different from the one we try to give it here; but then
again the context (being inside a function definition) is unique and
easily recognizable.

I consider that excessively verbose as well as misleading.

It is excessively verbose for the same reason as:

let y equal x plus 1

would be considered excessively verbose. I'm very fond of some languages
with verbose syntax, like Hypertalk and OpenXION where you might say "add
1 to x", but I don't want Python to become them.

It's a judgement call as to where a language divides "cryptic punctuation
line noise" and "useful short operators", and in my opinion * and ** tuple
and dict unpacking fall strongly on the "useful short operators" side.
Your opinion may differ, but luckily for me, the BDFL agrees with me

It is also misleading because args are not collected into a list, but
into a tuple. Worse, it suggests that one should be able to generalise to
something like this:

def func(parg, str(args), int(kwargs), my_func(more_args)):

which is incoherent.

And lastly, this would require either promoting list and dict to proper
keywords, which will not happen, or worse, making them semi-keywords
(treated as keywords in some contexts, but not in others), which also
will not happen.

Problems im still wrestling with: the same syntax could not be used when
calling a function; that lack of symmetry would make things more
confusing, not less.
Precisely.


Thoughts?

People learn to spell strings "like this" instead of str(like this), and
to use # for comments instead of REMARK or REM. It's not that much of a
burden on them to learn to use * and **