Moving from java to python.
Paul Hankin
paul.hankin at gmail.com
Mon Nov 12 16:42:47 CET 2007
On Nov 12, 3:25 pm, "PeterBrad... at googlemail.com"
<PeterBrad... at googlemail.com> wrote:
> Hi,
>
> I have recently been learning python, and coming from a java
> background there are many new ways of doing things that I am only just
> getting to grips with.
>
> I wondered if anyone could take a look at a few pieces of code I have
> written to see if there are any places where I am still using java-
> esque techniques, and letting me know the appropriate python way of
> doing things.
>
> Here is a node class I wrote for use in graph traversal algorithms:
>
> #====
>
> class Node:
> """
> Node models a single piece of connected data.
>
> Author: Peter Braden
> Last Modified : Nov. '07
> """
>
> def __init__(self, connections = None, uid = None):
> """
> Args:
> [connections - a list of (connected node, weight) tuples. ]
> [uid - an identifier for comparisons.]
> """
> self._connected = []
> self._weights = []
>
> if connections:
> for i in connections:
> self.connected.append(i[0])
> self.weights.append(i[1])
>
> if not uid:
> self.id = id(self)
> else:
> self.id = uid
>
> def __eq__(self, other):
> return self.id == other.id
>
> def getConnected(self):
> return self._connected
>
> def getWeights(self):
> return self._weights
>
> def getConnections(self):
> connections = []
> for i in range(len(connected)):
> connections.append((self._connected[i],self._weight[i]))
> return connections
>
> connected = property(getConnected, None)
> weights = property (getWeights, None)
> connections = property(getConnections, None)
>
> def addConnection(self, node, weight = 0):
> self.connected.append(node)
> self.weights.append(weight)
>
> def removeConnection(self, node):
> i = self._connected.index(node)
> del self._connected[i]
> del self._weights[i]
There's no reason to make 'connected' and 'weights' properties: just
use them directly.
Make 'connections' default to [] rather than None, and replace the
slightly clumsy initialisation with more direct code:
self.connected = [i[0] for i in connections]
self.weights = [i[1] for i in connections]
getConnections can be much simpler...
def getConnections(self):
return zip(self.connected, self.weights)
The 'uid' business makes me suspicious: what's it for? If you need it,
you probably need to initialise with an explicit test for None rather
than just 'if uid' which will be wrong if you use a uid of 0...
self.id = uid if uid is not None else id(self)
HTH
--
Paul Hankin
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