Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Nov 15, 2007 12:48 PM, Steven Bethard [EMAIL PROTECTED] wrote: On Nov 14, 2007 1:18 PM, Brett Cannon [EMAIL PROTECTED] wrote: On Nov 14, 2007 10:30 AM, Isaac Morland [EMAIL PROTECTED] wrote: So I wrote a Signature class. Instances of the class represent all the information present between the parentheses of a procedure definition. Properties are provided to get the information out, and an expand_args method can be called to expand arguments into a dictionary. This expand_args method implements (if I've done it right) the argument conversion part of section 5.3.4 of the Python Reference Manual (http://docs.python.org/ref/calls.html). As Collin already pointed out, it sounds like you want PEP 362 to get into the stdlib. I have not made a big push to try to get my existing implementation into Python 2.6/3.0, but I plan to at some point. Every time I read PEP 362, I get lost in the details. When you get around to working on it again, could you add a bunch of examples? That would make it much easier to tell why we want all those objects and attributes. You might not need them in general. It just re-packages all the information that is found between a function object and a code object into a single location. FWIW, Isaac's version of bind() that returns a regular str-object dict is all I've ever needed in my own code. That's what the implementation does at the moment (if I remember correctly). I am about to bundle up the code and submit to PyPI to get feedback from folks and to just get it out there instead of languishing in the sandbox while I try to decide exactly what to do about the open issues. I will see if i can toss in some examples into the PEP. -Brett ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Nov 15, 2007 12:48 PM, Steven Bethard [EMAIL PROTECTED] wrote: On Nov 14, 2007 1:18 PM, Brett Cannon [EMAIL PROTECTED] wrote: On Nov 14, 2007 10:30 AM, Isaac Morland [EMAIL PROTECTED] wrote: So I wrote a Signature class. Instances of the class represent all the information present between the parentheses of a procedure definition. Properties are provided to get the information out, and an expand_args method can be called to expand arguments into a dictionary. This expand_args method implements (if I've done it right) the argument conversion part of section 5.3.4 of the Python Reference Manual (http://docs.python.org/ref/calls.html). As Collin already pointed out, it sounds like you want PEP 362 to get into the stdlib. I have not made a big push to try to get my existing implementation into Python 2.6/3.0, but I plan to at some point. Every time I read PEP 362, I get lost in the details. When you get around to working on it again, could you add a bunch of examples? That would make it much easier to tell why we want all those objects and attributes. Done. I tossed up an annotations duck typing checker in the PEP. FWIW, Isaac's version of bind() that returns a regular str-object dict is all I've ever needed in my own code. My implementation does that as well. It was a typo in the PEP that said bind() returned Parameter objects as values. -Brett ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Wed, 14 Nov 2007, Brett Cannon wrote:
As Collin already pointed out, it sounds like you want PEP 362 to get
into the stdlib. I have not made a big push to try to get my existing
implementation into Python 2.6/3.0, but I plan to at some point.
Yes, it had not occurred to me to check the existing PEPs for my PEP
before proposing it. Now that I've read it I have a couple of comments,
but it is close to what I'm looking for.
I've put the code below, but I wonder if the real solution is just to create
an
interface to already-existing capability? It occurs to me that the
implementation is likely to be in the interpreter itself and not written in
Python.
I don't see why a Python implementation is bad. If you make this
information lazy then it is not such a big deal to have it take a
little bit longer than if it was implemented in C.
I don't have any problem with a Python implementation. In particular, I'm
not concerned in this case about the performance. Rather what I actually
wanted was a way to just bind arguments and then get the resulting
dictionary (what would usually become locals()). I realized that I could
create a Signature object with a binding method, but that I would just be
duplicating part of the Python interpreter.
I haven't studied the Python interpreter so I don't know if it is feasible
to re-use that (presumably highly optimized for actually calling
procedures, not just binding arguments) code or if it makes more sense to
simply re-implement it.
One possible improvement (and I'm not sure it's better, so I'm just putting
it
out there): perhaps expand_args should be renamed to __call__. Then
essentially
a Signature object would be a procedure whose body is just return locals
().
__call__ is already used a method name for objects that can be called.
Yes, that is why I used that name. The idea is that a Signature object be
callable, have itself as signature, and return the dictionary of locals
resulting from the procedure call argument binding process.
You can also think of (my idea of) Signature objects as providing a simple
way to create lots of special-case dictionary constructors.
More (semi-)formally, if the body of a procedure p is return locals (),
then p(...) is the same as p.__signature__(...).
A couple of comments about PEP-362:
1. For the name attribute of the Parameter object, I think it needs to
be str | tuple(str) | tuple(tuple(str)) | :
def a ((b,c),(d,(e,f))):
... print b,c,d,e,f
...
a
function a at 0x7899b0
a((1,2),(3,(4,5)))
1 2 3 4 5
2. For position of keyword-only parameters, are they allowed to conflict
with each other, or does each parameter get a unique value? +1 on not
using -1 as a special value. Python is not COBOL.
3. (My apologies if any of these have already been discussed) Under
Implementation, could __signature__ just be a property of callable
objects? Not saying anything about implementation, but just being able to
say formataddr.__signature__ feels nicely minimal (to me).
4. Signature.bind - for what I'm doing, I definitely want what would
become locals() in a procedure call, i.e. keys in the resulting dictionary
are strings. But I can see the other behaviour being useful in other
circumstances so maybe there should be bind and bindp, or (see above)
__call__ and bind, or something else.
5. var_args... default to None. +10 from me on this one - this is
*exactly* what None is, as far as I can tell. I'm new enough that this
should probably count for at most +0.1 though.
6. The PEP doesn't say anything about building Signature objects from
scratch, and the code does not reassure me. I would like to be able to
build a Signature from a sequence of strings for positional parameter
names, for example, and provide default values for some parameters. My
solution started off:
class Signature (object):
def __init__ (self, argnames,
excessargs=None, excesskeys=None, defaults=None):
self.__argnames = tuple (argnames)
self.__excessargs = excessargs
self.__excesskeys = excesskeys
if defaults is None:
defaults = {}
self.__defaults = dict (defaults)
[]
Thanks for the responses. I hope the above is at least in part not a
re-hash of old discussions.
Isaac Morland CSCF Web Guru
DC 2554C, x36650WWW Software Specialist
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Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Thu, 15 Nov 2007, Isaac Morland wrote: 1. For the name attribute of the Parameter object, I think it needs to be str | tuple(str) | tuple(tuple(str)) | : No, that's still wrong. I think it needs to be T, where T == str | tuple(T). Isaac Morland CSCF Web Guru DC 2554C, x36650WWW Software Specialist ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Nov 15, 2007 8:42 AM, Isaac Morland [EMAIL PROTECTED] wrote: On Wed, 14 Nov 2007, Brett Cannon wrote: As Collin already pointed out, it sounds like you want PEP 362 to get into the stdlib. I have not made a big push to try to get my existing implementation into Python 2.6/3.0, but I plan to at some point. Yes, it had not occurred to me to check the existing PEPs for my PEP before proposing it. Now that I've read it I have a couple of comments, but it is close to what I'm looking for. I've put the code below, but I wonder if the real solution is just to create an interface to already-existing capability? It occurs to me that the implementation is likely to be in the interpreter itself and not written in Python. I don't see why a Python implementation is bad. If you make this information lazy then it is not such a big deal to have it take a little bit longer than if it was implemented in C. I don't have any problem with a Python implementation. In particular, I'm not concerned in this case about the performance. Rather what I actually wanted was a way to just bind arguments and then get the resulting dictionary (what would usually become locals()). I realized that I could create a Signature object with a binding method, but that I would just be duplicating part of the Python interpreter. I haven't studied the Python interpreter so I don't know if it is feasible to re-use that (presumably highly optimized for actually calling procedures, not just binding arguments) code or if it makes more sense to simply re-implement it. One possible improvement (and I'm not sure it's better, so I'm just putting it out there): perhaps expand_args should be renamed to __call__. Then essentially a Signature object would be a procedure whose body is just return locals (). __call__ is already used a method name for objects that can be called. Yes, that is why I used that name. The idea is that a Signature object be callable, have itself as signature, and return the dictionary of locals resulting from the procedure call argument binding process. You can also think of (my idea of) Signature objects as providing a simple way to create lots of special-case dictionary constructors. More (semi-)formally, if the body of a procedure p is return locals (), then p(...) is the same as p.__signature__(...). Fair enough, but I prefer having a method for it. A couple of comments about PEP-362: 1. For the name attribute of the Parameter object, I think it needs to be str | tuple(str) | tuple(tuple(str)) | : def a ((b,c),(d,(e,f))): ... print b,c,d,e,f ... a function a at 0x7899b0 a((1,2),(3,(4,5))) 1 2 3 4 5 You are taking annotations a little too far in terms of typing. =) There are no type checks for the annotations; they are for documentation purposes only. Plus tuple parameters are gone as of Py3K thanks to my prodding to ditch them so I am really not going to worry about them now. =) 2. For position of keyword-only parameters, are they allowed to conflict with each other, or does each parameter get a unique value? +1 on not using -1 as a special value. Python is not COBOL. It is just he numeric order that the arguments are found, period. Keyword-only arguments are given a index position, it just doesn't really mean much other than giving it a numeric position. 3. (My apologies if any of these have already been discussed) Under Implementation, could __signature__ just be a property of callable objects? Not saying anything about implementation, but just being able to say formataddr.__signature__ feels nicely minimal (to me). The idea has been to add the code to the stdlib and let people try them out first. If they ended up being used often enough then discussion of putting a signature object on every callable could be discussed. 4. Signature.bind - for what I'm doing, I definitely want what would become locals() in a procedure call, i.e. keys in the resulting dictionary are strings. But I can see the other behaviour being useful in other circumstances so maybe there should be bind and bindp, or (see above) __call__ and bind, or something else. I only want to bother supporting one or the other. Doing the reverse is one or two lines of code. 5. var_args... default to None. +10 from me on this one - this is *exactly* what None is, as far as I can tell. I'm new enough that this should probably count for at most +0.1 though. 6. The PEP doesn't say anything about building Signature objects from scratch, and the code does not reassure me. That's because there is no way. =) I would like to be able to build a Signature from a sequence of strings for positional parameter names, for example, and provide default values for some parameters. My solution started off: class Signature (object): def __init__ (self, argnames, excessargs=None, excesskeys=None, defaults=None):
Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Nov 14, 2007 1:18 PM, Brett Cannon [EMAIL PROTECTED] wrote: On Nov 14, 2007 10:30 AM, Isaac Morland [EMAIL PROTECTED] wrote: So I wrote a Signature class. Instances of the class represent all the information present between the parentheses of a procedure definition. Properties are provided to get the information out, and an expand_args method can be called to expand arguments into a dictionary. This expand_args method implements (if I've done it right) the argument conversion part of section 5.3.4 of the Python Reference Manual (http://docs.python.org/ref/calls.html). As Collin already pointed out, it sounds like you want PEP 362 to get into the stdlib. I have not made a big push to try to get my existing implementation into Python 2.6/3.0, but I plan to at some point. Every time I read PEP 362, I get lost in the details. When you get around to working on it again, could you add a bunch of examples? That would make it much easier to tell why we want all those objects and attributes. FWIW, Isaac's version of bind() that returns a regular str-object dict is all I've ever needed in my own code. STeVe -- I'm not *in*-sane. Indeed, I am so far *out* of sane that you appear a tiny blip on the distant coast of sanity. --- Bucky Katt, Get Fuzzy ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
[Python-Dev] Python Library Addition: First-class Procedure Signatures
For another project (see my previous email on named tuples), I needed to
represent procedure signatures, and use them to expand arguments into the
dictionary of values that exists when execution of a procedure starts. To my
surprise, this capability didn't seem to be provided by the Python library,
even though it clearly is present within the Python system somewhere.
So I wrote a Signature class. Instances of the class represent all the
information present between the parentheses of a procedure definition.
Properties are provided to get the information out, and an expand_args method
can be called to expand arguments into a dictionary. This expand_args method
implements (if I've done it right) the argument conversion part of section
5.3.4 of the Python Reference Manual (http://docs.python.org/ref/calls.html).
I've put the code below, but I wonder if the real solution is just to create an
interface to already-existing capability? It occurs to me that the
implementation is likely to be in the interpreter itself and not written in
Python.
One possible improvement (and I'm not sure it's better, so I'm just putting it
out there): perhaps expand_args should be renamed to __call__. Then essentially
a Signature object would be a procedure whose body is just return locals ().
class Signature (object):
def __init__ (self, argnames,
excessargs=None, excesskeys=None, defaults=None):
self.__argnames = tuple (argnames)
self.__excessargs = excessargs
self.__excesskeys = excesskeys
if defaults is None:
defaults = {}
self.__defaults = dict (defaults)
@property
def argnames (self):
return self.__argnames
@property
def excessargs (self):
return self.__excessargs
@property
def excesskeys (self):
return self.__excesskeys
def defaults (self):
return dict (self.__defaults)
def expand_args (self, *args, **keys):
# Start with defaults
result = self.defaults ()
# Assign positional arguments
for i in range (min (len (args), len (self.argnames))):
result[self.argnames[i]] = args[i]
# Assign keyword arguments
for arg in self.argnames:
if arg in keys:
if arg in result:
raise TypeError
result[arg] = keys[arg]
del keys[arg]
# Check for missing arguments
for i in range (len (args), len (self.argnames)):
if not self.argnames[i] in result:
raise TypeError
# Excess positional arguments (*args parameter)
if self.excessargs is None:
if len (args) len (self.argnames):
raise TypeError
else:
result[self.excessargs] = args[len (self.argnames):]
# Excess keyword arguments (**keys parameter)
if self.excesskeys is None:
if keys:
raise TypeError
else:
result[self.excesskeys] = keys
return result
Isaac Morland CSCF Web Guru
DC 2554C, x36650WWW Software Specialist
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Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Nov 14, 2007 10:30 AM, Isaac Morland [EMAIL PROTECTED] wrote: For another project (see my previous email on named tuples), I needed to represent procedure signatures, and use them to expand arguments into the dictionary of values that exists when execution of a procedure starts. To my surprise, this capability didn't seem to be provided by the Python library, even though it clearly is present within the Python system somewhere. So I wrote a Signature class. Instances of the class represent all the information present between the parentheses of a procedure definition. Properties are provided to get the information out, and an expand_args method can be called to expand arguments into a dictionary. This expand_args method implements (if I've done it right) the argument conversion part of section 5.3.4 of the Python Reference Manual (http://docs.python.org/ref/calls.html). Have you seen http://www.python.org/dev/peps/pep-0362/? It sounds awfully similar to what you're proposing here. Collin Winter ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
Re: [Python-Dev] Python Library Addition: First-class Procedure Signatures
On Nov 14, 2007 10:30 AM, Isaac Morland [EMAIL PROTECTED] wrote: For another project (see my previous email on named tuples), I needed to represent procedure signatures, and use them to expand arguments into the dictionary of values that exists when execution of a procedure starts. To my surprise, this capability didn't seem to be provided by the Python library, even though it clearly is present within the Python system somewhere. So I wrote a Signature class. Instances of the class represent all the information present between the parentheses of a procedure definition. Properties are provided to get the information out, and an expand_args method can be called to expand arguments into a dictionary. This expand_args method implements (if I've done it right) the argument conversion part of section 5.3.4 of the Python Reference Manual (http://docs.python.org/ref/calls.html). As Collin already pointed out, it sounds like you want PEP 362 to get into the stdlib. I have not made a big push to try to get my existing implementation into Python 2.6/3.0, but I plan to at some point. I've put the code below, but I wonder if the real solution is just to create an interface to already-existing capability? It occurs to me that the implementation is likely to be in the interpreter itself and not written in Python. I don't see why a Python implementation is bad. If you make this information lazy then it is not such a big deal to have it take a little bit longer than if it was implemented in C. One possible improvement (and I'm not sure it's better, so I'm just putting it out there): perhaps expand_args should be renamed to __call__. Then essentially a Signature object would be a procedure whose body is just return locals (). __call__ is already used a method name for objects that can be called. -Brett ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
