Practice python Questions!

Given a custom Python class A, how can we make class A abstract?

• custom Python classes are always abstract

• specify the "abstract" keyword in one of its methods

• specify "raise NotImplemented()" in one of its methods

Given a custom Python class A and subclasses B, C, and D that all contain a method op() with the same code. Where would be the preferred class to specify the method op() and its implementation?

• include op() only in A

• include op() in B, C, and D

• no preferred location

Given a custom Python class A and its subclasses B, C, and D, where all four classes contain a method op(). How can we ensure that the method op() in class A cannot be executed:

• make the method op() in class A abstract

• we don't need to do anything in particular

• it's not possible to do this

Given a custom Python class A and this code snippet: myobj1 = A() x = myobj1 + 7 y = 7 + myobj1 We can ensure that the preceding statements succeed by:

• implementing the __add__() method

• implementing the __radd__() method

• no need for extra code

Queues are useful for the following types of use cases:

• scheduling tasks for execution (e.g., processes)

• checking if expressions contain balanced parentheses

• almost any type of use case involving trees

Stacks are useful for the following types of use cases:

• handling prefix and postfix expressions

• checking if expressions contain balanced parentheses

• almost any type of use case involving trees

A custom Python generator will:

• include the yield keyword

• be more efficient in terms of memory usage

• does not have particular advantages

Algorithms for graphs typically restrict graphs so that they:

• exclude only negative cycles

• exclude any type of cycle

• nothing is excluded

An acyclic graph is a graph without:

• vertices

• edges

• cycles

• tree

A graph is a tree if and only if:

• Every pair of vertices in the graph is connected by exactly one edge.

• The graph contains a single cycle.

• There is a unique path between every pair of vertices in the graph.

• There are no cycles in the graph, and it is connected.