Re: Another form of dynamic import
On 2009-03-25, Marco Nawijn wrote: > Hello, > > In short I would like to know if somebody knows if it is possible to > re-execute a statement that raised an exception? I will explain the > reason by providing a small introduction on why this might be nice in > my case > and some example code. > > I am using the python bindings to a *very* large C++ library. About > 5000 classes divided over approx. 450 different > packages are exposed through the Python interface. To reduce the > number of import statements that need to be inserted and to limit the > number of wildcard imports it would be very helpful if class names > could be automatically imported from the proper module. There is no > problem in finding out the proper module given a (valid) class name. Maybe this helps: http://www.connellybarnes.com/code/autoimp/ Regards, Anton -- http://mail.python.org/mailman/listinfo/python-list
Re: Another form of dynamic import
Also, instead of caching exceptions you can do lazy lookups kinda like this: - # a.py class A: pass - # b.py class B: pass - # c.py class D: pass class E: pass - # iface.py class LazyInterface(object): _attr_dict = dict(A='a', B='b', C='c', D='c') _attr_cache = dict() _mod_cache = dict() def __getattr__(self, name): if name in self._attr_cache: return self._attr_cache[name] elif name in self._attr_dict: module_name = self._attr_dict[name] self._mod_cache[module_name] = self._mod_cache.get(module_name,__import__(module_name)) self._attr_cache[name] = getattr(self._mod_cache[module_name], name) return self._attr_cache[name] else: raise AttributeError >>> from iface import LazyInterface >>> i = LazyInterface() >>> a = i.A() >>> a >>> c = i.C() >>> c >>> d = i.D() >>> d There is probably a cleaner/more robust way of doing the above, but you get the idea. -- http://mail.python.org/mailman/listinfo/python-list
Re: Another form of dynamic import
Marco Nawijn wrote: In short I would like to know if somebody knows if it is possible to re-execute a statement that raised an exception? In short, no. As an example, look at the following statement aPoint = gp_Pnt(1.0, 0.0, 0.0) # Oops, this will raise a NameError, since # gp_Pnt class is unknown NameError: name 'gp_Pnt' is not defined Either make sure names are defined before you use them (easy) or provide alternative code in the except clause. If you actually have the name written literally in the code, you should simply import it first, so I presume you have a more complicated use case where the name to use is dynamically defined in a string. If so, do something like aPoint = MyImporter(class_name)(1.0, 0.0, 0.0) where MyImporter.__new__ imports and returns the class Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Another form of dynamic import
On Mar 25, 10:23 am, Marco Nawijn wrote: > Hello, > > In short I would like to know if somebody knows if it is possible to > re-execute a statement that raised an exception? I will explain the > reason by providing a small introduction on why this might be nice in > my case > and some example code. > > I am using the python bindings to a *very* large C++ library. About > 5000 classes divided over approx. 450 different > packages are exposed through the Python interface. To reduce the > number of import statements that need to be inserted and to limit the > number of wildcard imports it would be very helpful if class names > could be automatically imported from the proper module. There is no > problem in finding out the proper module given a (valid) class name. > > As an example, look at the following statement > > >> aPoint = gp_Pnt(1.0, 0.0, 0.0) # Oops, this will raise a NameError, > >> since > > # gp_Pnt class > is unknown > > NameError: name 'gp_Pnt' is not defined > > As indicated, this will raise a NameError exception. What I would like > to do is something like the following (pseudo-code): > > try: > > > aPoint = gp_Pnt(1.0, 0.0, 0.0) [1] > > > > except NameError, e: > > name = e.args[0].split[1] > > if isValid(name): > doImport(name) > ===> Can I go back to statement [1] from this point? > else: > raise e > > There is no problem in catching the exception, finding out which name > is unknown to python and check if this is a valid name for my library. > My question is, is there any possibility of going back to the > statement that raised the error, re-execute the statement and > continue? > > Thanks for any thoughts and suggestions. > > Marco You can always use a loop: recover=True while True: try: aPoint = gp_Pnt(1.0, 0.0, 0.0)[1] except NameError, e: if recover: recover=False name = e.args[0].split[1] if isValid(name): doImport(name) else: raise e else: break -- http://mail.python.org/mailman/listinfo/python-list
Re: Another form of dynamic import
On 25 Mrz., 15:23, Marco Nawijn wrote: > Hello, > > In short I would like to know if somebody knows if it is possible to > re-execute a statement that raised an exception? I will explain the > reason by providing a small introduction on why this might be nice in > my case > and some example code. > > I am using the python bindings to a *very* large C++ library. About > 5000 classes divided over approx. 450 different > packages are exposed through the Python interface. To reduce the > number of import statements that need to be inserted and to limit the > number of wildcard imports it would be very helpful if class names > could be automatically imported from the proper module. There is no > problem in finding out the proper module given a (valid) class name. > > As an example, look at the following statement > > >> aPoint = gp_Pnt(1.0, 0.0, 0.0) # Oops, this will raise a NameError, > >> since > > # gp_Pnt class > is unknown > > NameError: name 'gp_Pnt' is not defined > > As indicated, this will raise a NameError exception. What I would like > to do is something like the following (pseudo-code): > > try: > > > aPoint = gp_Pnt(1.0, 0.0, 0.0)[1] > > > > except NameError, e: > > name = e.args[0].split[1] > > if isValid(name): > doImport(name) > ===> Can I go back to statement [1] from this point? > else: > raise e > > There is no problem in catching the exception, finding out which name > is unknown to python and check if this is a valid name for my library. > My question is, is there any possibility of going back to the > statement that raised the error, re-execute the statement and > continue? > > Thanks for any thoughts and suggestions. > > Marco There is no call/cc continuation in Python when you are asking for such a thing. I wonder however why you don't try lazy attribute access? Instead of making a raw function call like that to gp_Pnt, one can thread all calls to the C++ system through an object that implements __getattr__ and loads new names incrementally if one is missing. -- http://mail.python.org/mailman/listinfo/python-list
Another form of dynamic import
Hello, In short I would like to know if somebody knows if it is possible to re-execute a statement that raised an exception? I will explain the reason by providing a small introduction on why this might be nice in my case and some example code. I am using the python bindings to a *very* large C++ library. About 5000 classes divided over approx. 450 different packages are exposed through the Python interface. To reduce the number of import statements that need to be inserted and to limit the number of wildcard imports it would be very helpful if class names could be automatically imported from the proper module. There is no problem in finding out the proper module given a (valid) class name. As an example, look at the following statement >> aPoint = gp_Pnt(1.0, 0.0, 0.0) # Oops, this will raise a NameError, since # gp_Pnt class is unknown NameError: name 'gp_Pnt' is not defined As indicated, this will raise a NameError exception. What I would like to do is something like the following (pseudo-code): try: aPoint = gp_Pnt(1.0, 0.0, 0.0)[1] except NameError, e: name = e.args[0].split[1] if isValid(name): doImport(name) ===> Can I go back to statement [1] from this point? else: raise e There is no problem in catching the exception, finding out which name is unknown to python and check if this is a valid name for my library. My question is, is there any possibility of going back to the statement that raised the error, re-execute the statement and continue? Thanks for any thoughts and suggestions. Marco -- http://mail.python.org/mailman/listinfo/python-list
