Python classes from a for loop

Question

I've got a piece of code which contains a for loop to draw things from an XML file;

   for evoNode in node.getElementsByTagName('evolution'):
      evoName    = getText(evoNode.getElementsByTagName(        "type")[0].childNodes)
      evoId      = getText(evoNode.getElementsByTagName(      "typeid")[0].childNodes)
      evoLevel   = getText(evoNode.getElementsByTagName(       "level")[0].childNodes)
      evoCost    = getText(evoNode.getElementsByTagName("costperlevel")[0].childNodes)

      evolutions.append("%s x %s" % (evoLevel, evoName))

Currently it outputs into a list called evolutions as it says in the last line of that code, for this and several other for functions with very similar functionality I need it to output into a class instead.

class evolutions:
    def __init__(self, evoName, evoId, evoLevel, evoCost)
        self.evoName = evoName
        self.evoId = evoId
        self.evoLevel = evoLevel
        self.evoCost = evoCost

How to create a series of instances of this class, each of which is a response from that for function? Or what is a core practical solution? This one doesn't really need the class but one of the others really does.

a note about style, you should always name classes with camel case starting with a capital letter, and they shouldn't be plural. It should be: class Evolution — Soviut
– Soviut, Commented Jan 13, 2009 at 20:39
You can also remove the 'evo' prefix from the class fields, they can be inferred from the context of the class. Saves typing. :) — Craz
– Craz, Commented Jan 13, 2009 at 20:50
Don't Repeat Yourself (DRY): get = lambda name: getText(evoNode.getElementsByTagName(name)[0].childNodes) — jfs
– jfs, Commented Aug 30, 2009 at 12:10

Jorenko · Accepted Answer · 2009-01-13 20:57:14Z

4

A list comprehension might be a little cleaner. I'd also move the parsing logic to the constructor to clean up the implemenation:

class Evolution:
    def __init__(self, node):
        self.node = node
        self.type = property("type")
        self.typeid = property("typeid")
        self.level = property("level")
        self.costperlevel = property("costperlevel")
    def property(self, prop):
        return getText(self.node.getElementsByTagName(prop)[0].childNodes)

evolutionList = [Evolution(evoNode) for evoNode in node.getElementsByTagName('evolution')]

Alternatively, you could use map:

evolutionList = map(Evolution, node.getElementsByTagName('evolution'))

edited Jan 13, 2009 at 20:57

answered Jan 13, 2009 at 20:51

Jorenko

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1 Comment

jfs Over a year ago

property is a built-in function in Python. It is a bad style to use it the way you did. docs.python.org/library/functions.html#property

Teifion · Accepted Answer · 2009-01-13 20:40:44Z

3

for evoNode in node.getElementsByTagName('evolution'):
  evoName      = getText(evoNode.getElementsByTagName("type")[0].childNodes)
  evoId      = getText(evoNode.getElementsByTagName("typeid")[0].childNodes)
  evoLevel   = getText(evoNode.getElementsByTagName("level")[0].childNodes)
  evoCost      = getText(evoNode.getElementsByTagName("costperlevel")[0].childNodes)

  temporaryEvo = Evolutions(evoName, evoId, evoLevel, evoCost)
  evolutionList.append(temporaryEvo)

  # Or you can go with the 1 liner
  evolutionList.append(Evolutions(evoName, evoId, evoLevel, evoCost))

I renamed your list because it shared the same name as your class and was confusing.

edited Jan 13, 2009 at 20:40

answered Jan 13, 2009 at 20:35

Teifion

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2 Comments

S.Lott Over a year ago

Could you also rename their class to be Uppercase, like Proper Class Names Should Be?

Teifion Over a year ago

I thought that was just me that put classes as Uppercase for the first letter. Or do you mean all letters?

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