Week 4

Question 1

What is abstraction?

Answer 1

It is the notion of retaining the releveant details for a given context and ignoring the irrelevant details.

Question 2

What are simple/atomic data types?

Answer 2

These are data types that can be represented in data values which CANNOT be further divided.

Question 3

What are examples of atomic data types?

Answer 3

Int
Str
Bool
Float

Question 4

What are complex data types?

Answer 4

These are datatypes that represent collections of multiple data values

Question 5

What are examples of complex data types?

Answer 5

Lists
Dictionaries
Tuples
Strings
Sets

Question 6

What are abstract data types (ADTs)?

Answer 6

These are complex data types which specifies a set of data values AND a set of operations that can be perfomed on these data values.

i.e. a function

Question 7

What are characteristics of literal values?

Answer 7

• They are objects

- As objects they require a certain amount of memory to hold data value

Question 8

What are array-based structures?

Answer 8

The data items in this collection are organised and stored SEQUENTIALLY in a contigous block of memory.

Individual data items are located at the adjacent memory blocks.

Question 9

How can you access data in an array-based data structure? Why does this method work?

Answer 9

Using indexing as the data is ordered.

Question 10

What are link-based structures?

Answer 10

A data structure where the data items for a colection can be situated at ANY locations within memory.

The data items are linked together using the concept of ‘referencing’ the address of the subsequent item.

Question 11

Can data in a link-based structure be accessed randomly?

Answer 11

No, since the data is not adjacent to each other in memory.

Question 12

How can you access an item i in a link-based structure?

Answer 12

First you must begin at the first node, and traverse to the node that is linked to the initial node until reaching item i.

Question 13

When are array-based structured preferred?

Answer 13

When the total number of elements in a data collection can be predetermined at the START of the program implementation.

When accesssing data elements at random.

This is due as array-based structures generally takes less memory compared to link-based structures at equal ‘fullness’.

Question 14

When are link-based structured prefered?

Answer 14

If adding new elements and removing existing elements at random positions.

Question 15

What is mutability?

Answer 15

It is the ability to modify an item.

Question 16

What does it mean when an object is immutable?

Answer 16

This means that the object cannot be modified.

Question 17

Are string immutable or mutable?

Answer 17

Immutable.

Question 18

Are lists immutable or mutable?

Answer 18

Mutable

Question 19

What is an item assignment? Does it work for strings? Does it work for lists?

Answer 19

It is when you assign a variable to an item.

Only works for lists, not strings as strings are immutable.

Question 20

How would you replace an item in a string and return/print out the modified string?

Answer 20

Have to create a new variable which concatenates the item to be added and the index of where it should be added.

Question 21

Are tuples immutable or mutable?

Answer 21

Immutable

Question 22

What is aliasing?

Answer 22

When you assign two different names to the same object

Question 23

What is a dictionary?

Answer 23

It is a build it mapping data type in python. It assigns a value to a key. The value can then be accessed by determining the key.

Question 24

Are dictionaries unordered?

Answer 24

Yes