Leiden python meetup: memory graph - Bas Terwijn¶

Tags: pun, python

(One of my summaries of the fifth Python meetup in Leiden, NL).

Full title of the talk: memory graph: teaching tool and debugging aid in context of references, mutable data types, and shallow and deep copy.

memory_graph is a python debugging aid and teaching tool. It is a modern version of python tutor. (There is an online demo)

Python has two categories of types:

• Immutable types: bool, int, float, str, tuple, etcetera. They cannot be mutated, so when a value is changed, a copy is made. If you add an item to a tuple, you get a new tuple with the extra item.

• Mutable types: dicts, lists. You can change the values without the actual dict/list changing. You can add items to a list and you still have the same list object.

When you want an actual copy of a mutable type, you need to use import copy and copy.copy(your_list). And copy.deepcopy().

• list2 = list1 is an assignment.

• list2 = copy.copy(list1) gives you a second, separate, list object, but it points at the same values inside it as list1.

• list2 = copy.deepcopy(list1) gives you a second, separate, list object and separate copies of the values inside it.

Watch out with the list2 = list1 assignment. When you add an item to list2, it is also “added” to list1 as it is the same.

He had a couple of simple exercises for us, which were amusingly hard :-)

Apart from the web online demo, there are also integrations for jupyter notebooks and lots of IDEs. Here’s an animated gif from the github repo: