Hi,
Revisiting a fairly old discussion...
Conversations in the past have occurred around this sort of thing:
import time
from Kamaelia.Util.Backplane import Backplane, PublishTo, SubscribeTo
from Kamaelia.Chassis.Pipeline import Pipeline
from Kamaelia.Chassis.ServerCore import ServerCore
from Kamaelia.File.Append import Append
from Kamaelia.Util.PureTransformer import PureTransformer
def log_events (**argd):
peer = str(argd.get(peer, ""))
return Pipeline(
PureTransformer(lambda x: peer + “|” + x),
PublishTo("UI_EVENTS")
)
Backplane("UI_EVENTS").activate()
Pipeline(
SubscribeTo("UI_EVENTS"),
PureTransformer(lambda x: str(time.time()+”|”+x),
Append(filename = "userlog.txt"),
).activate()
ServerCore(protocol=log_events, port=1500).run()
Specifically with regard to the import lines:
from Kamaelia.Util.Backplane import Backplane, PublishTo, SubscribeTo
from Kamaelia.Chassis.Pipeline import Pipeline
from Kamaelia.Chassis.ServerCore import ServerCore
from Kamaelia.File.Append import Append
from Kamaelia.Util.PureTransformer import PureTransformer
Comments regarding this:
* "It's nice and clear precisely what's being imported"
* "It's clear where they've come from"
* "It's daunting for a newbie"
* "How would I find the correct components myself?"
http://www.kamaelia.org/Components is the "correct" answer,
but the point stands.
* "That hierarchy makes no sense to me, X should by in A.B.C not in A.D.E"
These comments become even more important with larger applications.
Similarly it was mooted that this could be simplified by flattening the
hierarchy completely. The problem with this is when browsing
through /Components, it can actually help alot having the hierachy, simply
because hierarchies can be easier to navigate than everything in one
directory. (Hence /usr/bin , /opt/<thing>/bin, /usr/local/bin, etc)
Since I wasn't aware of any autoload (like perl has) functionality in python,
I'd decided to leave this for now, but today I got curious about trying it
again. After a bit of searching I came across a post, and played around a bit
and came up with this:
# mymod.py
def greet(greeting="Hello World"):
print greeting
class autoload(object):
def __init__(self, __name__):
super(autoload, self).__init__()
self.wrapped_name = __name__
self.wrapped = sys.modules[__name__]
def __getattr__(self, name):
try:
return getattr(self.wrapped, name)
except AttributeError:
def f():
greet(name+" "+self.wrapped_name)
return f
if __name__ != "__main__":
import sys
sys.modules[__name__] = autoload(__name__)
This can then be used like this:
>>> from mymod import Pipeline, TCPClient, use_as_component
>>> Pipeline()
Pipeline mymod
>>> TCPClient()
TCPClient mymod
>>> use_as_component()
use_as_component mymod
>>>
This clearly allows, given some work, the above example to be rewritten as
follows:
import time
from Kamaelia import Backplane, PublishTo, SubscribeTo, \
Pipeline, ServerCore, Append, PureTransformer
def log_events (**argd):
peer = str(argd.get(peer, ""))
return Pipeline(
PureTransformer(lambda x: peer + “|” + x),
PublishTo("UI_EVENTS")
)
Backplane("UI_EVENTS").activate()
Pipeline(
SubscribeTo("UI_EVENTS"),
PureTransformer(lambda x: str(time.time()+”|”+x),
Append(filename = "userlog.txt"),
).activate()
ServerCore(protocol=log_events, port=1500).run()
Which is IMO much more friendly.
So some questions arise:
1. Good idea or not?
2. Really? Could be viewed as bad mojo & messing about one step too far.
3. If OK, should it be static? ie the list of what gets imported and
handles what dealt with by a table lookup in Kamaelia/__init__.py ?
4. Or should it go "OK, I was imported here, I'll rummage around in all my
subdirectories, in this overall order"
5. Do 3, then 4, if the name wasn't found in 3.
6. The other way round ?
7. Do we allow extra search paths for the case of 4 ? (think sys.path for
modules)
8. How about allowing extra lookup tables to be added in the case of 3?
9. lots more possibilities.
For the moment, if I was to do this I'd probably do "3" initially, then
change "3" to be autogenerated (from Kamaelia.Support.Data.Repository).
However, I'm pausing, since, aside from anything else, I'm not sure what level
of aversion other people might have to autoloading like this. Personally I
think it's a good option, but open to comments. (Tempted to give a lightning
talk at europython on autoloading in general to gauge opinion)
Regards,
Michael.
--
http://yeoldeclue.com/blog
http://twitter.com/kamaelian
http://www.kamaelia.org/Home
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