Harri Hämäläinen

1. Answer each of the following questions with a few sentences.

(a) Why do you think Python developers chose to make instances of
    types str and tuple immutable?

Some suggestions:
- immutable types can be used in places, where mutable types such lists are
  not allowed, such as keys for dictionary
- performance, the size of the immutable object cannot change during run time

Grading: +1 point / valid reasoning, 2 points at maximum


(b) When should some functionality be provided by functions and when
    by classes and their methods?

Some suggestions:
- classes are often used to model some state of your program, methods in
  classes are one way to change that state
- operations which don't affect to the state of program are usually better to
  be implemented as functions, if their functionality is not related to any of
  your classes

Grading: +1 point if told when to use functions, +1 point if told when to use
methods


(c) What are the main differences and commonalities between the containers dict
and list?

Some suggestions:
- lists and dicts both support iteration
- both are mutable
- dict is a key-value mapping where items are accessed by the key
- list is a positionally ordered container where items are accessed by the 
  index

Grading: +0.5 / valid (difference | commonality), rounded up


(d) Why is the Method Resolution Order (MRO) needed in Python?

Some suggestions:
- MRO defines the order in which base classes are visited when call for
  some attribute occurs
- when multiple inheritance is used, basic bottom-up approach might cause
  ambiguous results - better be explicit!

Grading: +1 point if just given the reason without any explanation, +1
point if answer also shows an example of case when it's needed or
describes how MRO finds the correct definition