Running code from an imported file in Python

Question

I have two files, multitest.py and skiplist.py We are given skiplist.py as starter code that we cannot edit.

multitest.py is the file I'm supposed to create and borrow the functions from skiplist.py

In the skiplist.py file, we have a method like

class SkipList(object):
    def __len__(self):
        """(SkipList) -> int
        Return the number of items in this skip list.
        """
        return self.size

In multitest.py, I will have to create my own len method, but I am not allowed to access any built-ins.

from skiplist import *
class MultiSet(object):
    def __len__(self):
        """(MultiSet) -> int
        Return the number of items in this multiset.
        """
        return SkipList.__len__(self)

When running

s = MultiSet([])
print(len(s))

I get the error

Traceback (most recent call last):
File "/Applications/WingIDE.app/Contents/MacOS/src/debug/tserver/_sandbox.py", line 134, in <module>
File "/Applications/WingIDE.app/Contents/MacOS/src/debug/tserver/_sandbox.py", line 56, in __len__
File "/Users/Borna/Documents/CSC148/Assignment/skiplist.py", line 39, in __len__
return self.size
builtins.AttributeError: 'MultiSet' object has no attribute 'size'

technically object is a builtin, so...

Wooble
– Wooble

2013-02-13 19:45:03 +00:00
Commented Feb 13, 2013 at 19:45 — Wooble
– Wooble, Commented Feb 13, 2013 at 19:45

nneonneo · Accepted Answer · 2013-02-13 19:44:32Z

4

Well, your MultiSet doesn't inherit from SkipList so it should not call any methods of SkipList on itself. In this case, as you can see, SkipList has a .size attribute but MultiSet does not.

To fix this, you'll have to either make MultiSet extend SkipList (class MultiSet(SkipList)), or implement MultiSet.__len__ without using SkipList methods directly (e.g. by having MultiSet contain an instance of SkipList and returning that instance's size).

answered Feb 13, 2013 at 19:44

nneonneo

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1 Comment

user1754499 Over a year ago

I tried inheritance via class MultiSet(SkipList) and got the exact same error.

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