Re: [IronPython] Decorators on classes
Dino Viehland wrote: This might be something fun to look at during the sprints at PyCon. I will definitely be staying for the sprints - either as part of a Resolver sprint or under my own steam... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Foord Sent: Monday, February 04, 2008 2:55 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Hello Dino, That sounds *great*, and is something really needed by IronPython. How long do you think it will take you to implement? 0.5 wink Michael http://www.manning.com/foord Dino Viehland wrote: Ok, maybe it's a little optimistic or maybe it needs a couple of hooks exposed, but it's not too crazy. As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator such as: def ClrAttribute(attr): def attrFunc(class): # do something smart here with attr return attrFunc @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): @ClrAttribute(SomeOtherAttribte) def DoSomething(self): return 42 As Curt mentioned we do a bunch of caching and such with NewTypeMaker and maybe spit out a new type. That's all going to happen before the decorator gets to run - but we'll only create a new type once so there isn't too much overhead here :). From there you could copy that type w/ Reflection.Emit but add the attribute(s) on it, and then create a new instance of it passing in the PythonType object to its constructor (that's how Python types work - the instance holds onto a copy of the PythonType, the one problem here being that the UnderlyingSystemType of the PythonType would now be wrong, so that might need a hook). This could also include applying the attributes to methods and potentially manifesting concretely typed methods. This same sort of approach might even work w/ a meta-class. Plugging into NewTypeMaker would simplify this but I don't think makes it impossible. There's also other potential problems with systems based up types and attributes: Sometimes they want a type that lives in an assembly and sometimes they want to create instances of types (and they don't know to pass in a PythonType object to the constructor). -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Foord Sent: Monday, February 04, 2008 2:03 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. Is that right - could attributes be added to an IronPython class (or instances) at runtime using reflection? Earlier parts of this conversation implied that this wasn't the case... Decorators are only syntactic sugar, so the lack of class decorators isn't an impediment... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes
Re: [IronPython] Decorators on classes
Keith J. Farmer wrote: Py3k has ASTs, right? .. if the ASTs were mapped to System.Linq.Expressions wherever possible, that would be a great start. Even better if we got complaints if trying to cast an expression that couldn't be cast to the CLR nodes. Well - Python has had ASTs from the start through the compiler package: http://docs.python.org/lib/compiler.html The compiler contains libraries to generate an abstract syntax tree from Python source code and to generate Python bytecode from the tree. This is only available in FePy and not straight IronPython. Additionally, there's a super-secret _ast module in Python 2.5. Documented in the dev docs for 2.6 http://docs.python.org/dev/library/_ast.html The compiler package *is* being replaced in Python 3, but I don't know the details and a quick googling didn't reveal anything. Not sure how this helps with LINQ though as I don't believe that Python 3 ASTs will allow you to modify the grammar - so it could only help if you pass in your queries as strings? (Which is problematic as they need access to the enclosing namespace of course.) Michael http://www.manning.com/foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 4:09 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: from future import clr_hacks sounds like the start of an awfully slippery slope. lol :-) Although I do recall suggesting a while back that it might be impossible to avoid incompatible syntax if we are to have full LINQ support in IronPython, and that a future import would be one way to go... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curt Hagenlocher Sent: Monday, February 04, 2008 2:54 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 2:27 PM, Dino Viehland [EMAIL PROTECTED] wrote: As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator You could theoretically have a slightly alternate parsing mode that recognizes a specific class decorator name before the class definition is closed (and therefore before codegen). In other words, the following definition @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): treats the decorator differently if it matches one of the special-case names. The change in parsing could be triggered by something like from future import clr_hacks. On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
In our project 98% of attributes are on class definition and properties. The 2% left are field attributes, [field: NonSerialized()], on user defined events. On Feb 5, 2008 1:07 AM, Keith J. Farmer [EMAIL PROTECTED] wrote: My personal experience says that the most prevalent use of attributes in .NET *is* on methods and properties, as part of the original class definition. Consider: LINQ to SQL: http://msdn2.microsoft.com/en-us/library/bb386971.aspx WCF: http://linqinaction.net/blogs/jwooley/archive/2007/05/14/wcf-with-the-linq-to-sql-designer.aspx XML Serialization: http://www.devhood.com/Tutorials/tutorial_details.aspx?tutorial_id=236 It is rather ugly. :-) Thanks; I thought so myself. Would this technique have anything to offer for attributes on methods and properties (etc). It's hard to see how, but it's been a while since I looked at that part of the source. I'm pretty sure that the CLR class itself needs to be emitted entirely by the contents of the one class statement -- and well before the first method is defined. Which means that none of the properties or methods of the class could influence codegen. Frankly, I don't think that attributes on methods or properties are realistic -- at least, not as part of the original class definition. What I think you'd be looking at is the ability to define a class wrapper that wraps the initially-defined dynamic class with a new statically-defined class that allows you to put attributes on methods and properties. Hmm... where have I heard that recently... :) ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
I am only an egg. The basic requirement for IQueryable (and, by extension as it were, the interesting variations of LINQ providers) is that the compiler be able to emit a series of calls to build expressions. I only imagine (read: I haven't studied Python's AST offerings) that *for the most part* it should be a fairly straightforward mapping of a subset to the new Expressions namespace. Enough that probably a fairly simple visitor could transform from one to the other. Using dotted notation for the query operators themselves is okay. Creating new Expression trees is a PITA without help. From: [EMAIL PROTECTED] on behalf of Fuzzyman Sent: Tue 2/5/2008 3:12 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: Py3k has ASTs, right? .. if the ASTs were mapped to System.Linq.Expressions wherever possible, that would be a great start. Even better if we got complaints if trying to cast an expression that couldn't be cast to the CLR nodes. Well - Python has had ASTs from the start through the compiler package: http://docs.python.org/lib/compiler.html The compiler contains libraries to generate an abstract syntax tree from Python source code and to generate Python bytecode from the tree. This is only available in FePy and not straight IronPython. Additionally, there's a super-secret _ast module in Python 2.5. Documented in the dev docs for 2.6 http://docs.python.org/dev/library/_ast.html The compiler package *is* being replaced in Python 3, but I don't know the details and a quick googling didn't reveal anything. Not sure how this helps with LINQ though as I don't believe that Python 3 ASTs will allow you to modify the grammar - so it could only help if you pass in your queries as strings? (Which is problematic as they need access to the enclosing namespace of course.) Michael http://www.manning.com/foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 4:09 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: from future import clr_hacks sounds like the start of an awfully slippery slope. lol :-) Although I do recall suggesting a while back that it might be impossible to avoid incompatible syntax if we are to have full LINQ support in IronPython, and that a future import would be one way to go... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curt Hagenlocher Sent: Monday, February 04, 2008 2:54 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 2:27 PM, Dino Viehland [EMAIL PROTECTED] wrote: As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator You could theoretically have a slightly alternate parsing mode that recognizes a specific class decorator name before the class definition is closed (and therefore before codegen). In other words, the following definition @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): treats the decorator differently if it matches one of the special-case names. The change in parsing could be triggered by something like from future import clr_hacks. On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use of .NET attributes not just on properties, but on classes themselves. Being able to express these attributes in IronPython is a tremendous bonus. That there be one and only one way to express these is paramount. ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use of .NET attributes not just on properties, but on classes themselves. Being able to express these attributes in IronPython is a tremendous bonus. That there be one and only one way to express these is paramount. ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use of .NET attributes not just on properties, but on classes themselves. Being able to express these attributes in IronPython is a tremendous bonus. That there be one and only one way to express these is paramount. ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use of .NET attributes not just on properties, but on classes themselves. Being able to express these attributes in IronPython is a tremendous bonus. That there be one and only one way to express these is paramount. ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use of .NET attributes not just on properties, but on classes themselves. Being able to express these attributes in IronPython is a tremendous bonus. That there be one and only one way to express these is paramount. ___ Users mailing list Users@lists.ironpython.com http
Re: [IronPython] Decorators on classes
Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use of .NET attributes not just on properties, but on classes themselves. Being able to express these attributes in IronPython is a tremendous bonus. That there be one and only one way to express these is paramount. ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Here's an implementation idea that may require less work at the expense of less-elegant syntax. class X(object, clr.AttributeBase(System.SerializableAttribute)) pass NewTypeMaker would look for base classes of whatever built-in type is returned by clr.AttributeBase and would use that information to decorate the generated type. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Dino Viehland wrote: FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. Is that right - could attributes be added to an IronPython class (or instances) at runtime using reflection? Earlier parts of this conversation implied that this wasn't the case... Decorators are only syntactic sugar, so the lack of class decorators isn't an impediment... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers will be making heavy use
Re: [IronPython] Decorators on classes
Python decorators may be sugar, but .NET Attributes are not -- they're metadata that there's no way to emit, currently, without using Reflection API arcana, and no way to append to a type or member that already exists. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 2:02 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. Is that right - could attributes be added to an IronPython class (or instances) at runtime using reflection? Earlier parts of this conversation implied that this wasn't the case... Decorators are only syntactic sugar, so the lack of class decorators isn't an impediment... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes
Re: [IronPython] Decorators on classes
Keith J. Farmer wrote: Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. Ok - but unless you want *howls* of outrage from the Python community that had better be done in a way compatible with Python syntax. I really like the way the IronPython team chose to add support for typing (e.g. Array[int]) by overloading existing syntax rather than adding new syntax. For the record I think that reusing Python decorators is *fine* as they are at least analogous concepts even if not identical. I *agree* that being able to access attributes is important to IronPython and really want this to happen... The problem is that attributes can be applied to properties, arguments and return values - which don't sit so well with Python decorators. Nesting class decorators to specify the target could work, and they could be applied at parse/compile time rather than runtime. (With the cost that classes with attributes applied are probably not garbage collectable as they mean creating unique CLR classes.) Michael Foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces plus attributes). It's definitely doable, but raises intriguing questions about purity. And you'd also need to consider the impact on the larger DLR. Method-level attributes are an entirely different matter. On Feb 4, 2008 10:58 AM, Michael Foord [EMAIL PROTECTED] wrote: Class decorators will be in Python 2.6 - but there is a big difference between a Python runtime decorator and .NET compile time attributes. Is it possible to attach attributes at runtime using the reflection API? Michael http://www.manning.com/foord Keith J. Farmer wrote: Can I resurrect this forgotten soul? http://www.codeplex.com/WorkItem/View.aspx?ProjectName=IronPythonWorkItemId=13583 Having just finished working on LINQ to SQL, I'm convinced that future LINQ providers
Re: [IronPython] Decorators on classes
Ok, maybe it's a little optimistic or maybe it needs a couple of hooks exposed, but it's not too crazy. As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator such as: def ClrAttribute(attr): def attrFunc(class): # do something smart here with attr return attrFunc @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): @ClrAttribute(SomeOtherAttribte) def DoSomething(self): return 42 As Curt mentioned we do a bunch of caching and such with NewTypeMaker and maybe spit out a new type. That's all going to happen before the decorator gets to run - but we'll only create a new type once so there isn't too much overhead here :). From there you could copy that type w/ Reflection.Emit but add the attribute(s) on it, and then create a new instance of it passing in the PythonType object to its constructor (that's how Python types work - the instance holds onto a copy of the PythonType, the one problem here being that the UnderlyingSystemType of the PythonType would now be wrong, so that might need a hook). This could also include applying the attributes to methods and potentially manifesting concretely typed methods. This same sort of approach might even work w/ a meta-class. Plugging into NewTypeMaker would simplify this but I don't think makes it impossible. There's also other potential problems with systems based up types and attributes: Sometimes they want a type that lives in an assembly and sometimes they want to create instances of types (and they don't know to pass in a PythonType object to the constructor). -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Foord Sent: Monday, February 04, 2008 2:03 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. Is that right - could attributes be added to an IronPython class (or instances) at runtime using reflection? Earlier parts of this conversation implied that this wasn't the case... Decorators are only syntactic sugar, so the lack of class decorators isn't an impediment... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes
Re: [IronPython] Decorators on classes
We would need this to apply to what would be CLR properties, fields, and methods. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 3:17 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Here's an implementation idea that may require less work at the expense of less-elegant syntax. class X(object, clr.AttributeBase(System.SerializableAttribute)) pass NewTypeMaker would look for base classes of whatever built-in type is returned by clr.AttributeBase and would use that information to decorate the generated type. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Curt Hagenlocher wrote: Here's an implementation idea that may require less work at the expense of less-elegant syntax. class X(object, clr.AttributeBase(System.SerializableAttribute)) pass NewTypeMaker would look for base classes of whatever built-in type is returned by clr.AttributeBase and would use that information to decorate the generated type. That wouldn't play well with metaclasses, which isn't a showstopper. It is rather ugly. :-) Would this technique have anything to offer for attributes on methods and properties (etc). Michael -- Curt Hagenlocher [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Hello Dino, That sounds *great*, and is something really needed by IronPython. How long do you think it will take you to implement? 0.5 wink Michael http://www.manning.com/foord Dino Viehland wrote: Ok, maybe it's a little optimistic or maybe it needs a couple of hooks exposed, but it's not too crazy. As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator such as: def ClrAttribute(attr): def attrFunc(class): # do something smart here with attr return attrFunc @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): @ClrAttribute(SomeOtherAttribte) def DoSomething(self): return 42 As Curt mentioned we do a bunch of caching and such with NewTypeMaker and maybe spit out a new type. That's all going to happen before the decorator gets to run - but we'll only create a new type once so there isn't too much overhead here :). From there you could copy that type w/ Reflection.Emit but add the attribute(s) on it, and then create a new instance of it passing in the PythonType object to its constructor (that's how Python types work - the instance holds onto a copy of the PythonType, the one problem here being that the UnderlyingSystemType of the PythonType would now be wrong, so that might need a hook). This could also include applying the attributes to methods and potentially manifesting concretely typed methods. This same sort of approach might even work w/ a meta-class. Plugging into NewTypeMaker would simplify this but I don't think makes it impossible. There's also other potential problems with systems based up types and attributes: Sometimes they want a type that lives in an assembly and sometimes they want to create instances of types (and they don't know to pass in a PythonType object to the constructor). -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Foord Sent: Monday, February 04, 2008 2:03 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. Is that right - could attributes be added to an IronPython class (or instances) at runtime using reflection? Earlier parts of this conversation implied that this wasn't the case... Decorators are only syntactic sugar, so the lack of class decorators isn't an impediment... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having
Re: [IronPython] Decorators on classes
Keith J. Farmer wrote: I'm fine with something like @clrAttribute[attributeType](targetIdentifier, args). I'm interested in the feature more than I am in quibbling over specific syntax. That said, I question the value of syntax compatibility when the API just doesn't exist. When is CPython ever going to run something that depends on the existance of CLR-isms? Adding the support within existing CPy syntax only buys our beloved BDFL the freedom to guide syntax unilaterally. Not a bad thing, mind, and I'm happy to see Guido retain that power, but that's the only practical benefit. CPythonista outrage over not being able to read something they could never run is rather silly. :) I would see it as more of a concern that IronPython is no longer a faithful implementation of Python but a hybrid language that is mostly Python and partly something of Microsoft's invention. Python has been evolved gradually and gracefully under the hands of Guido, the core developers and the community. Microsoft has no place introducing incompatible syntax and wanting the community to still think of it as Python. I'm sure the IronPython team are aware of this. :-) Michael http://www.manning.com/foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 2:09 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. Ok - but unless you want *howls* of outrage from the Python community that had better be done in a way compatible with Python syntax. I really like the way the IronPython team chose to add support for typing (e.g. Array[int]) by overloading existing syntax rather than adding new syntax. For the record I think that reusing Python decorators is *fine* as they are at least analogous concepts even if not identical. I *agree* that being able to access attributes is important to IronPython and really want this to happen... The problem is that attributes can be applied to properties, arguments and return values - which don't sit so well with Python decorators. Nesting class decorators to specify the target could work, and they could be applied at parse/compile time rather than runtime. (With the cost that classes with attributes applied are probably not garbage collectable as they mean creating unique CLR classes.) Michael Foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class
Re: [IronPython] Decorators on classes
I'm fine with something like @clrAttribute[attributeType](targetIdentifier, args). I'm interested in the feature more than I am in quibbling over specific syntax. That said, I question the value of syntax compatibility when the API just doesn't exist. When is CPython ever going to run something that depends on the existance of CLR-isms? Adding the support within existing CPy syntax only buys our beloved BDFL the freedom to guide syntax unilaterally. Not a bad thing, mind, and I'm happy to see Guido retain that power, but that's the only practical benefit. CPythonista outrage over not being able to read something they could never run is rather silly. :) From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 2:09 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. Ok - but unless you want *howls* of outrage from the Python community that had better be done in a way compatible with Python syntax. I really like the way the IronPython team chose to add support for typing (e.g. Array[int]) by overloading existing syntax rather than adding new syntax. For the record I think that reusing Python decorators is *fine* as they are at least analogous concepts even if not identical. I *agree* that being able to access attributes is important to IronPython and really want this to happen... The problem is that attributes can be applied to properties, arguments and return values - which don't sit so well with Python decorators. Nesting class decorators to specify the target could work, and they could be applied at parse/compile time rather than runtime. (With the cost that classes with attributes applied are probably not garbage collectable as they mean creating unique CLR classes.) Michael Foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact, the similarities are superficial at best. .NET attributes are totally static, so there's no way to modify a .NET class definition to add them. The IronPython engine would have to recognize particular class-level Pythonic annotations and use that information to emit a new CLR class to represent the Python class. It already emits CLR classes as needed to represent Python classes. By as needed, I mean that a specific CLR base class plus a specific set of CLR interfaces will uniquely determine a class to be emitted by IronPython. This class is cached so that -- once generated -- any new Python class definition that matches this set of (CLR base class plus interfaces) will reuse the same CLR class definition. What you'd have to change is to put the class-level attributes onto the generated CLR class, then change caching so that the key is (CLR base class plus interfaces
Re: [IronPython] Decorators on classes
Dino Viehland wrote: from future import clr_hacks sounds like the start of an awfully slippery slope. lol :-) Although I do recall suggesting a while back that it might be impossible to avoid incompatible syntax if we are to have full LINQ support in IronPython, and that a future import would be one way to go... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curt Hagenlocher Sent: Monday, February 04, 2008 2:54 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 2:27 PM, Dino Viehland [EMAIL PROTECTED] wrote: As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator You could theoretically have a slightly alternate parsing mode that recognizes a specific class decorator name before the class definition is closed (and therefore before codegen). In other words, the following definition @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): treats the decorator differently if it matches one of the special-case names. The change in parsing could be triggered by something like from future import clr_hacks. On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
On the contrary, I have no problem whatsoever envisioning any outrageous headline on Slashdot, regardless of the actual facts. I left that crowd many years ago. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 2:54 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
On Feb 4, 2008 3:29 PM, Michael Foord [EMAIL PROTECTED] wrote: It is rather ugly. :-) Thanks; I thought so myself. Would this technique have anything to offer for attributes on methods and properties (etc). It's hard to see how, but it's been a while since I looked at that part of the source. I'm pretty sure that the CLR class itself needs to be emitted entirely by the contents of the one class statement -- and well before the first method is defined. Which means that none of the properties or methods of the class could influence codegen. Frankly, I don't think that attributes on methods or properties are realistic -- at least, not as part of the original class definition. What I think you'd be looking at is the ability to define a class wrapper that wraps the initially-defined dynamic class with a new statically-defined class that allows you to put attributes on methods and properties. Hmm... where have I heard that recently... :) -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
This might be something fun to look at during the sprints at PyCon. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Foord Sent: Monday, February 04, 2008 2:55 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Hello Dino, That sounds *great*, and is something really needed by IronPython. How long do you think it will take you to implement? 0.5 wink Michael http://www.manning.com/foord Dino Viehland wrote: Ok, maybe it's a little optimistic or maybe it needs a couple of hooks exposed, but it's not too crazy. As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator such as: def ClrAttribute(attr): def attrFunc(class): # do something smart here with attr return attrFunc @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): @ClrAttribute(SomeOtherAttribte) def DoSomething(self): return 42 As Curt mentioned we do a bunch of caching and such with NewTypeMaker and maybe spit out a new type. That's all going to happen before the decorator gets to run - but we'll only create a new type once so there isn't too much overhead here :). From there you could copy that type w/ Reflection.Emit but add the attribute(s) on it, and then create a new instance of it passing in the PythonType object to its constructor (that's how Python types work - the instance holds onto a copy of the PythonType, the one problem here being that the UnderlyingSystemType of the PythonType would now be wrong, so that might need a hook). This could also include applying the attributes to methods and potentially manifesting concretely typed methods. This same sort of approach might even work w/ a meta-class. Plugging into NewTypeMaker would simplify this but I don't think makes it impossible. There's also other potential problems with systems based up types and attributes: Sometimes they want a type that lives in an assembly and sometimes they want to create instances of types (and they don't know to pass in a PythonType object to the constructor). -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Foord Sent: Monday, February 04, 2008 2:03 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: FYI IP 2.0 is tracking 2.5 and we have the big pieces in place plus many small pieces (although there's more to go). In 1.1 we had -X:Python25 which enabled selective 2.5 features and we could conceptually do the same sort of thing for 2.0 so that it includes one or two 2.6 features such as class decorators. From there the decorators to support attributes could even be written in Python. Is that right - could attributes be added to an IronPython class (or instances) at runtime using reflection? Earlier parts of this conversation implied that this wasn't the case... Decorators are only syntactic sugar, so the lack of class decorators isn't an impediment... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Keith J. Farmer Sent: Monday, February 04, 2008 1:40 PM To: Discussion of IronPython; Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very
Re: [IronPython] Decorators on classes
from future import clr_hacks sounds like the start of an awfully slippery slope. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curt Hagenlocher Sent: Monday, February 04, 2008 2:54 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 2:27 PM, Dino Viehland [EMAIL PROTECTED] wrote: As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator You could theoretically have a slightly alternate parsing mode that recognizes a specific class decorator name before the class definition is closed (and therefore before codegen). In other words, the following definition @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): treats the decorator differently if it matches one of the special-case names. The change in parsing could be triggered by something like from future import clr_hacks. On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Curt Hagenlocher wrote: On Feb 4, 2008 3:29 PM, Michael Foord [EMAIL PROTECTED] wrote: It is rather ugly. :-) Thanks; I thought so myself. Would this technique have anything to offer for attributes on methods and properties (etc). It's hard to see how, but it's been a while since I looked at that part of the source. I'm pretty sure that the CLR class itself needs to be emitted entirely by the contents of the one class statement -- and well before the first method is defined. Which means that none of the properties or methods of the class could influence codegen. Frankly, I don't think that attributes on methods or properties are realistic -- at least, not as part of the original class definition. What I think you'd be looking at is the ability to define a class wrapper that wraps the initially-defined dynamic class with a new statically-defined class that allows you to put attributes on methods and properties. Hmm... where have I heard that recently... :) Getting attributes on classes would be a start - but for example with Silverlight you would want to be able to mark methods as 'Scriptable'. It sounds like Dino has some ideas on this though. When I was thinking about auto generating static assemblies from Python source it did occur to me that it would be possible to use simple markers to enable attributes... Michael -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
My personal experience says that the most prevalent use of attributes in .NET *is* on methods and properties, as part of the original class definition. Consider: LINQ to SQL: http://msdn2.microsoft.com/en-us/library/bb386971.aspx WCF: http://linqinaction.net/blogs/jwooley/archive/2007/05/14/wcf-with-the-linq-to-sql-designer.aspx XML Serialization: http://www.devhood.com/Tutorials/tutorial_details.aspx?tutorial_id=236 From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 3:46 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 3:29 PM, Michael Foord [EMAIL PROTECTED] wrote: It is rather ugly. :-) Thanks; I thought so myself. Would this technique have anything to offer for attributes on methods and properties (etc). It's hard to see how, but it's been a while since I looked at that part of the source. I'm pretty sure that the CLR class itself needs to be emitted entirely by the contents of the one class statement -- and well before the first method is defined. Which means that none of the properties or methods of the class could influence codegen. Frankly, I don't think that attributes on methods or properties are realistic -- at least, not as part of the original class definition. What I think you'd be looking at is the ability to define a class wrapper that wraps the initially-defined dynamic class with a new statically-defined class that allows you to put attributes on methods and properties. Hmm... where have I heard that recently... :) -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
Py3k has ASTs, right? .. if the ASTs were mapped to System.Linq.Expressions wherever possible, that would be a great start. Even better if we got complaints if trying to cast an expression that couldn't be cast to the CLR nodes. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 4:09 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Dino Viehland wrote: from future import clr_hacks sounds like the start of an awfully slippery slope. lol :-) Although I do recall suggesting a while back that it might be impossible to avoid incompatible syntax if we are to have full LINQ support in IronPython, and that a future import would be one way to go... Michael -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curt Hagenlocher Sent: Monday, February 04, 2008 2:54 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes On Feb 4, 2008 2:27 PM, Dino Viehland [EMAIL PROTECTED] wrote: As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator You could theoretically have a slightly alternate parsing mode that recognizes a specific class decorator name before the class definition is closed (and therefore before codegen). In other words, the following definition @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): treats the decorator differently if it matches one of the special-case names. The change in parsing could be triggered by something like from future import clr_hacks. On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
On Feb 4, 2008 2:27 PM, Dino Viehland [EMAIL PROTECTED] wrote: As other people have pointed out decorators are a runtime concept and I don't think we get to change that. So consider a class decorator You could theoretically have a slightly alternate parsing mode that recognizes a specific class decorator name before the class definition is closed (and therefore before codegen). In other words, the following definition @ClrAttribute(System.SerializableAttribute) class X(ISomething, object): treats the decorator differently if it matches one of the special-case names. The change in parsing could be triggered by something like from future import clr_hacks. On Feb 4, 2008 2:32 PM, Keith J. Farmer [EMAIL PROTECTED] wrote: CPythonista outrage over not being able to read something they could never run is rather silly. :) You're clearly having trouble envisioning the following Slashdot headline: Microsoft inflicts 'embrace and extend' on Python. Silly or not, perceptions are hugely important. -- Curt Hagenlocher [EMAIL PROTECTED] ___ Users mailing list Users@lists.ironpython.com http://lists.ironpython.com/listinfo.cgi/users-ironpython.com
Re: [IronPython] Decorators on classes
If I can come to terms with Peter Jackson's portrayal of LotR... I said it was silly. I didn't say the reasons didn't exist. From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 2:46 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I'm fine with something like @clrAttribute[attributeType](targetIdentifier, args). I'm interested in the feature more than I am in quibbling over specific syntax. That said, I question the value of syntax compatibility when the API just doesn't exist. When is CPython ever going to run something that depends on the existance of CLR-isms? Adding the support within existing CPy syntax only buys our beloved BDFL the freedom to guide syntax unilaterally. Not a bad thing, mind, and I'm happy to see Guido retain that power, but that's the only practical benefit. CPythonista outrage over not being able to read something they could never run is rather silly. :) I would see it as more of a concern that IronPython is no longer a faithful implementation of Python but a hybrid language that is mostly Python and partly something of Microsoft's invention. Python has been evolved gradually and gracefully under the hands of Guido, the core developers and the community. Microsoft has no place introducing incompatible syntax and wanting the community to still think of it as Python. I'm sure the IronPython team are aware of this. :-) Michael http://www.manning.com/foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 2:09 PM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: Grandfathering: Giving more consideration to retaining compatibility than it deserves. :) Obviously, IronPython should prioritize compatibility with Py2.4, but for obvious reasons I limit that to seeing IP as a consumer of CPy, not the other way around. On the other hand, IP must also be able to consume .NET, and .NET is increasingly making use of things the IP cannot yet express. (I thought of another framework that attributes are used on -- WCF. There are also XML serialization attributes.) To that end, I think it would be worthwhile, for the purpose of .NET attributes, to have decorators or their analogues available to IronPython in the current stage of development. That is, I think it should be that IronPython = CPy 2.4 + .NET Attributes + other .NET-isms expressed in a Pythonic way. Ok - but unless you want *howls* of outrage from the Python community that had better be done in a way compatible with Python syntax. I really like the way the IronPython team chose to add support for typing (e.g. Array[int]) by overloading existing syntax rather than adding new syntax. For the record I think that reusing Python decorators is *fine* as they are at least analogous concepts even if not identical. I *agree* that being able to access attributes is important to IronPython and really want this to happen... The problem is that attributes can be applied to properties, arguments and return values - which don't sit so well with Python decorators. Nesting class decorators to specify the target could work, and they could be applied at parse/compile time rather than runtime. (With the cost that classes with attributes applied are probably not garbage collectable as they mean creating unique CLR classes.) Michael Foord From: [EMAIL PROTECTED] on behalf of Michael Foord Sent: Mon 2/4/2008 11:53 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Keith J. Farmer wrote: I've had no problems with not grandfathering in older APIs, and am quite happy to not grandfather in older syntax, either. What do you mean by 'grandfathering' in this context? Michael I agree that IronPython would have to be able to distinguish between CLR attributes and Python decorators, inasmuch as CLR attributes are a static part of the class/member definition. But I don't think it's an insurmountable problem, and solving it in the DLR, actually, would be very useful. I wouldn't expect that class authors would want to change the set of .NET attributes frequently if at all -- it doesn't match how they've been designed and how they've evolved, so creating the attributed base class once (and then having pythonic decorators coming in and out at will) seems like a reasonable approach to me. From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher Sent: Mon 2/4/2008 11:13 AM To: Discussion of IronPython Subject: Re: [IronPython] Decorators on classes Oh! I didn't realize that about 2.6. There is indeed a big difference between a Python runtime decorator and a .NET compile time attribute; in fact
