how to use new AST goodies
Hello, i've just found out that the ast-branch has been merged into the main python cvs. ** Woohoo ! ** I'd like to experiment with this, does anyone know where to start ? It seems that the parser module still produces the same junk as before. So where do we find these nice high level AST objects ? thanks, Simon. -- http://mail.python.org/mailman/listinfo/python-list
Re: namespace dictionaries ok?
Yes! I do this a lot when i have deeply nested function calls a->b->c->d->e and need to pass args to the deep function without changing the middle functions. In this situation I think i would prefer this variation: class Context(dict): def __init__(self,**kwds): dict.__init__(self,kwds) def __getattr__(self, name): return self.__getitem__(name) def __setattr__(self, name, value): self.__setitem__(name, value) def __delattr__(self, name): self.__delitem__(name) def foo(ctx): print ctx.color, ctx.size, ctx.shape foo( Context(color='red', size='large', shape='ball') ) This is looking like foo should be a method of Context now, but in my situation foo is already a method of another class. Simon. -- http://mail.python.org/mailman/listinfo/python-list
Re: namespace dictionaries ok?
In my case the deeply nested function calls are recursive calls for a tree traversal. This is similar to the visitor design pattern, where the Context class above is the Visitor. The difference is that the Context instance does not "visit" or "act" upon the nodes, but just stores state/context information about the current traversal. Simon. -- http://mail.python.org/mailman/listinfo/python-list
linking one extension module to another (Mac OSX)
Hi, I'm having some trouble linking one extension module to another because the linker expects a "lib" prefix and my python modules cannot have this prefix. I found two ways of doing it on a linux box (either symlink or create a dummy .so that links to extension module) but I can get neither of them work on OSX (let alone windows). Simon. -- http://mail.python.org/mailman/listinfo/python-list
if not DEBUG: log = null_log
Hi,
I'm after a no-op command, so that i can redirect
logging commands in performance critical code.
Something like this:
def log(*args): print args
def null_log(*args): pass
if not DEBUG: log = null_log
is unacceptable because of the overhead of calling
functions in python.
log ("about to slip into python feature request mode.")
Maybe this is what the PEP 336 guy was thinking of (Make None Callable).
Obviously we don't want None to be callable, but
what about a "Null" [1] that's callable, with any args ?
But I guess what I am really asking for is something on the bytecode
level that tells the VM to "do nothing".
Here's an idea: make "pass" into an expression (a value) that is callable,
with any args, and returns None.
log ("finished with python feature request mode.")
I recently discovered "pyc" [2], but i don't quite see how i can
use it while maintaining python source compatability.
bye!
Simon.
[1]: http://occs.cs.oberlin.edu/~jwalker/nullObjPattern/
[2]: http://students.ceid.upatras.gr/~sxanth/pyc/
--
Simon Burton, B.Sc.
Licensed PO Box 8066
ANU Canberra 2601
Australia
Ph. 61 02 6249 6940
http://arrowtheory.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: namespaces
I've been needing a module level __getattr__ for some c library
wrapping. This has solved the problem:
# mymod.py:
import sys
from new import module
class ModuleProxy(module):
def __init__( self, name, master ):
module.__init__( self, name )
self._master = master
self.__dict__["__all__"] = dir(master)
def __getattr__(self, name):
attr = getattr( self._master, name )
return attr
# ... end of file:
sys.modules["mymod"] = ModuleProxy("mymod",sys.modules["mymod"])
--Simon Burton
--
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PyCon Vs. Europython
My employer has given me the choice to go to either Pycon or Europython this year, and I need some help deciding which would be more useful (for me, my company, and python itself). I am mainly interested in scientific/engineering applications of python; and am keen to work on/learn about some of the more esoteric python projects, such as the AST integration, and PyPy. Participating in a sprint would be brilliant. The line-up of talks at this year's PyCon looks more interesting to me, compared to Europython 2005. thanks, Simon Burton. -- http://mail.python.org/mailman/listinfo/python-list
find class where method was defined ?
>>> >>> class A(object): ... def foo(self): pass ... >>> >>> class B(A): ... pass ... >>> >>> b=B() >>> b.foo > How can I work out what class b.foo was defined in ? Simon. -- http://mail.python.org/mailman/listinfo/python-list
Re: find class where method was defined ?
def methclass(meth): cls = meth.im_class name = meth.im_func.__name__ meth = getattr(cls,name,None) for cls in cls.mro(): _meth = getattr(cls,name,None) if _meth is not None and _meth==meth: result = cls return result >>> methclass(b.foo) (Turns out equality bypasses the methodwraper trickery.) Simon. -- http://mail.python.org/mailman/listinfo/python-list
compile your python programs with rpython
The pypy'ers have written a brief description on using rpython to create standalone executables: http://codespeak.net/pypy/dist/pypy/doc/standalone-howto.html This is definately worth playing around with, it's very nice writing (r)python code that gets executed as if it were c code. Simon. -- http://mail.python.org/mailman/listinfo/python-list
realization: no assignments inside expressions
I've been doing a little c programming again (ouch!) and it's just hit me why python does not allow assignment inside expressions (as in c): because it is absolutely essential that all assignments are as visible as possible. In python the assignment is the declaration; when declarations are as cheap as this it's hard not to fall to the temptation to re-use a variable unknowingly. I am constantly scanning the line of assignments to see what variables are already live, and I just realised how easy it is to do that. Up to now I guess I thought it was just a restriction to stop new users of python from writing too obfuscated code. wow. Simon. -- http://mail.python.org/mailman/listinfo/python-list
