Functions, Structured Types, Mutability, Sequences, Lists

Question 1

What makes good programming?

Answer 1

• amount of functionality
• introduce functions
• mechanisms to achieve decomposition and abstraction

–> more code not necessarily better

Question 2

What do you use abstraction for in programming?

How do you achieve it?

Answer 2

–> Suppress details

The process of removing details or attributes to focus attention on details of greater importance

Think of a piece of code as a black box and achieve abstraction using functions or docstrings

Question 3

What do you use decomposition for?

Answer 3

It involves breaking down a complex problem into smaller modules that are easier to understand. The smaller parts are simpler to work with.
Modules should be:
-self contained
-intended to be reused

Achieve decomposition using functions or classes

Question 4

What are functions?

Answer 4

Functions are reusable pieces of code that have to be called in a program (they do not run automatically)

A function has a name and a body and can have parameters, a docstring
A function should return something

Question 5

How do you write a function?

Answer 5

def  (): 
body
return

Question 6

How do you invoke a function?

Answer 6

you call it by writing its name with round backets and parameters if needed
i.e. is_even(3)

Question 7

What is the difference between a formal and a actual parameter?

Answer 7

The formal parameter is the one used i ´n the function definition and the actual one is the one that is called with the function when running –> formal parameter gets found to the value of the actual parameter when function is called

Question 8

What happens if you do not define a return statement ?

Answer 8

Python automatically returns value None, if no return is given

Question 9

What is the difference between print and return?

Answer 9

Return:

1. Only has a meaning inside a function
2. only one return executed inside a function
3. code after return statement not executed
4. Has a value associated with it and gives it to the function caller

Print

1. Can be used outside functions
2. Can execute several print statements within a function
3. Code inside a function can be executed after a print statement
4. The value associated to it will only be outputted to the console

Question 10

What are higher-order functions?

Answer 10

Functions that take functions as argument/parameter

Question 11

What is a list?

Answer 11

A list is a ordered sequence of information accessible by index

• -> A list is denoted by square brackets [] and contains elements
• -> can contain mixed types but usually homogenous i.e. all ints
• -> lists are mutable (can be changed)

Question 12

How do you iterate through a list L?

Answer 12

for elem in L:

body

Question 13

How do you access objects (like list instances)?

Answer 13

using the dot (.)

list_name.append(something)

Question 14

Can you convert a string s into a list L?

Answer 14

Yes, using list(s) –> returns a list with every character from s as an element in L

• -> use split to split a string on character parameter
• -> use ““.join to turn a list of characters into a string

Question 15

What is a Tuple?

Answer 15

1. A tuple is an ordered sequence of elements (can be of mixed type)
2. immutable - cannot change values
3. represented with parentheses
4. (2, “mit”, 3) + (5, 6) = (2, “mit”, 3, 5, 6)

Question 16

What are tuples often used for?

Answer 16

1. Used to return more than one value from a function
   return (q, r)
2. To swap variable values
   (x, y) = (y, x)

Question 17

What is recursion?

Answer 17

Algorithmically: a way to design solutions to problems by
divide-and-conquer

Semantically: a programming technique where a
function
calls itself
–> must have a base case

Question 18

What is a dictionary?

Answer 18

They store pairs of data in the form {key : value}
looks up the key –> return value
i.e. grades = {‘Ana’ : ‘B’, ‘John’ : ‘A+’}
grades[‘John’] –> returns ‘A+’

Question 19

Can values in a dictionary have mutable or immutable types?

Answer 19

Both!

Question 20

Can Values in dictionaries be duplicates?

Answer 20

Yes

Question 21

What properties do dictionary keys have?

Answer 21

1. Keys must be unique

2. Must be of immutable type (int, float, string, tuple, bool)

Question 22

What are the differences of lists and values?

Answer 22

Lists:

• ordered sequence of elements
• look up elements by an integer value
• indices have an order
• Index is an integer

Dict:

• matches keys to values
• look up one item by another item
• no order is guaranteed
• key can be any immutable type