How to view all the current objects and their immediate methods

Question

I am looking at this tutorial in twisted python. https://github.com/jdavisp3/twisted-intro/blob/master/twisted-client-3/get-poetry.py

def get_poetry(host, port, callback):
    """
    Download a poem from the given host and port and invoke

      callback(poem)

    when the poem is complete.
    """
    from twisted.internet import reactor
    factory = PoetryClientFactory(callback)#I am interested in checking the instances alive here
    reactor.connectTCP(host, port, factory)


def poetry_main():
addresses = parse_args()

from twisted.internet import reactor

poems = []

def got_poem(poem):
    poems.append(poem)
    if len(poems) == len(addresses):
        reactor.stop()

for address in addresses:
    host, port = address
    get_poetry(host, port, got_poem)

reactor.run()

for poem in poems:
    print poem


if __name__ == '__main__':
    poetry_main()

I have never really debugged python before.

I wanted to see which classes's instances are alive before the reactor.stop fires.

I was checking this Printing all instances of a class

with this code

import gc
for obj in gc.get_objects():

How can I selectively view the top most information and then further inherited data and so on?

From a twisted point of view, I want see which factory instances are currently active and how is it related to the protocols

Answer 1

But, if you really just want to poke things to get a feel for how to debug Python, check out 'dir(obj)', which will list all the properties and methods of an object.

class Blah(object):
    pass

b = Blah()

for x in dir(b):
    try:
        print getattr(b,x,False)
    except Exception, e:
        print x,e

Will yield:

<class '__main__.Blah'>
<method-wrapper '__delattr__' of Blah object at 0x1028ba490>
{}
None
<built-in method __format__ of Blah object at 0x1028ba490>
<method-wrapper '__getattribute__' of Blah object at 0x1028ba490>
<method-wrapper '__hash__' of Blah object at 0x1028ba490>
<method-wrapper '__init__' of Blah object at 0x1028ba490>
__main__
<built-in method __new__ of type object at 0x10276a4e0>
<built-in method __reduce__ of Blah object at 0x1028ba490>
<built-in method __reduce_ex__ of Blah object at 0x1028ba490>
<method-wrapper '__repr__' of Blah object at 0x1028ba490>
<method-wrapper '__setattr__' of Blah object at 0x1028ba490>
<built-in method __sizeof__ of Blah object at 0x1028ba490>
<method-wrapper '__str__' of Blah object at 0x1028ba490>
<built-in method __subclasshook__ of type object at 0x7fd522c6e490>

Now, your mileage may vary with stuff like objc - since it's a thin Python wrapper around making shared library calls. They won't have docstrings, or in some cases respond to 'dir' if function lookup is lazy-lookup against shared libraries. But, you never know.

Most of the time when it came to the objc stuff, I just dug around in their source code to figure out how they did things when the normal methods of digging up dirt didn't work.

Speaking of normal methods:

A neat feature with Twisted, you can also serve a telnet or SSH accessible interactive Python shell that can actually poke and prod things 'live'. Check here for details on TwistedConch.

Or..

Another trick is to add a 'del(self)', function to your objects that prints something out as the object gets cleaned up by the garbage collector (when it's deleted / out of scope)

Or..

You could also play with pdb, or if you like ncurses pudb is awesome. Check out this question for a couple nifty tricks for using pdb. starting-python-debugger-automatically-on-error

And, if worse comes to worse - you can always use help(object).

Those are pretty much the debugging methods that get me through the day. If anyone else has some clever ideas don't be shy.