Question

I’m python newbie and found something difficult while doing some practices.

I have few def functions under a class look like:

Class A(object):

    def __init__(self):

        self.itemID = []
        self.itemlist = []

    def add(self, ID, list):

        self.itemID.append(ID)
        self.itemlist.append(list)

    def get_item(self,ID):

        self.ID = ID
        result = []
        for self.ID in self.itemlist:
            result.append(self.itemlist)
        return result

I’m having problems with “def get_item”. Here’s an example..

if i do:

A.add('abc', 'bcd')

A.add('abc1', 'bcd1')

A.get_item('abc')

This should return abc, bcd but mine returns [[‘bcd’, ‘bcd1’], [‘bcd’, ‘bcd1’]]…

Apologise for the long complicated dumb looked codes…. Any feedbacks would be so appreciated.. Thanks

Answer 1

your get_item function is absolutely wrong 🙂

Here’s how it should look like:

def get_item(self,ID):
  result = []
  for x in range(0, len(self.itemID)):
      if (self.itemID[x] == ID):
          result.append(self.itemlist[x])
  return result

Or even better:

def get_item(self, ID):
   return [self.itemlist[x] for x in range(0, len(self.itemID) if self.itemID[x] == ID]

Now, if I understand the logic behind your class, you want to be able to retrieve a list of object given a common ID. This can be better done using a dict

class A:
   def __init__(self):
       self.content  = {}

   def add(self, ID, object):
       list = self.get_item(ID)
       list.append(object)
       content[ID] = list

   def get_item(self, ID):
       return content.get(ID, [])