W13

Question 1

What is the scope of Local variables?

Answer 1

Inside the function they are defined in.

Question 2

What does a variable scope mean?

Answer 2

The parts of the program in which the variable is visible (accessed or modified).

Question 3

Are parameter variables local or global?

Answer 3

Local

Question 4

What type of errors will occur when using a variable out of its scope?

Answer 4

A compiler error

Question 5

Can two different local variables have the same name and different values?

Answer 5

Yes

Question 6

Variables defined outside of functions are considered as what type of variables?

Answer 6

Global variables

Question 7

Global variables can be visible (accessed and modified) by what functions?

Answer 7

A global variable is visible to all functions that are defined after it.

Question 8

How can you create or modify a global variable inside a function?

Answer 8

Using the keyword “global”. Otherwise, instead of accessing the global variable, a local variable will be created with the same global variable name

Question 9

What are the Python collections?

Give an example

Answer 9

Collections are

containers that store data, such as Lists.

Question 10

What operator do you use to access a list element?

Answer 10

The subscript operator [ ].

Question 11

What operator do you use to create a list element?

Answer 11

The square brackets [ ].

Question 12

What operator do you use to print, access or modify a part of a list?

Answer 12

The slice operator [ n1 : n2 ]

Question 13

list[ : 6 ], what indexes will be printed?

Answer 13

from 0 to 5

Question 14

list[ 6 : ], what indexes will be printed?

Answer 14

from 6 to last index

Question 15

list[ 3 : 9 ], what indexes will be printed?

Answer 15

from 3 to 8

Question 16

You can assign new values to a slice.
Ex:
List [ 2 : 5 ] = [11, 21, 88]
True or False?

Answer 16

True

Question 17

list[-4]= equals what index???

list[-1]=equals what index???

Answer 17

list[-4] = list[last index - 3] or list[len(list)-4]

list[-1] = list[last index - 0] or list[len(list)-1]

Question 18

What type of errors will occur when accessing a non-existing list element?

Answer 18

A run-time error:

IndexError: list index out of range

Question 19

A list variable contains a “reference” to the list content?

True or False?

Answer 19

True
list_name (list variable)= [ content] (reference)--> which is the list's location in the memory

Question 20

What is Aliasing?

Answer 20

Aliasing is when two or more variables reference the same memory location.
The second variable is an alias for the first because both variables reference the same list

Question 21

s = [ 3, 4 , 8]
s=r
r[0]=10
print(s)

Answer 21

10, 4 , 8

Question 22

When passing a ‘list variable’ to a function’s parameter, modifying the parameter will not affect the original list?

True or False?

Answer 22

False.
This is called as ‘ Variables call by reference’.

Therefore, instead of modifying the parameter, pass the parameter to a new variable then do what you want.
Or, use ‘ Variables call by value’

Question 23

A Python function can mutate the contents of a list in the calling function because it receives a reference to the list
—the parameter variable becomes an alias for the original list.

True or False?

Answer 23

True.

Question 24

How to add elements to a list?

Answer 24

list.append()

Question 25

IMPORTANT!

summary

Answer 25

1- When you assign a list variable to another variable, both variables refer to the same list —this is true even when using list as arguments, the parameter variable becomes an alias.

2- lists are references to memory locations

3- lists are aliases

4- lists are containers

Question 26

A function that calls itself?

Answer 26

A recursive function

Question 27

For a recursion function to terminate, there must be a ?

Answer 27

Base case

Question 28

Every recursive call must simplify the computation in some way.
True or False

Answer 28

True.

Question 29

A that function calls itself over and over with no end in sight and your program
will shut down and report a “stack overflow”

Answer 29

The Infinite recursion function

Question 30

the one branch of the recursive function that does not call itself.

Answer 30

The base case. Therefore, they prevent infinite recursion

Question 31

A special purpose function which allow additional parameters to be used without modifying the recursive function

Answer 31

Helper function

Question 32

Disadvantages of recursive functions (list three):

Answer 32

More memory
Difficult to debug
Slower than using iteration

Question 33

“Mutable” vs. “Immutable”

Answer 33

changeable and unchangeable

Question 34

A process of using a loop to go over a group of items

Answer 34

Iteration