CODEWITHSUNDEEP
pythonlistclassobject
James Bellamy
James Bellamy

Reputation: 73

Creating a list of objects with a class in Python

I am trying to emulate a Java toString method I learned a while back. I might be off base here and there may definitely be an easier way to do what I'm trying to do with a simple list.

What I really want to do is be able to append objects to a list, and then print specific traits about those objects from the list. I also want to keep track of the index of the object. Here is what I have so far, but when I print, I get no errors, and a blank line, nothing prints.

class Character_list():
    def __init__(self, list):
        self.list = []

def toString(self):
    result = ""
    for i in self.list:
        result += self.list[i]

    return result

def main(): 
    x = Character_list([1, 2])
    print(x.toString())

main()

Upvotes: 0

Views: 7823

Answers (1)

user2390182
user2390182

Reputation: 73460

Three things:

First, use the parameter you pass to the constructor to actually instantiate your object

class Character_list():
    def __init__(self, lst):
        self.lst = lst  # use the parameter! And don't use 'list' as a variable name
        # or even better, use a shallow copy:
        self.lst = list(lst)

Second, python loops are generally for-each loops. That means you are iterating elements, not indexes. So 

    for i in self.lst:
        result += i

will actually append the list elements (which have to be strings, otherwise use: result += str(i)) to result.

Third, Python's version of toString is __str__ and is implicitly called when using the the built-in str() on an object. So, for instance

def __str__(self):
    return ''.join(map(str, self.lst))

will do what you intended, but more generally, e.g. when you call 

print(x)

Upvotes: 5

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