Boolean Values, Conditional Execution, Loops, Lists and List Processing, Logical and Bitwise Operations

Question 1

What is the difference between = and ==?

Answer 1

= is an assignment operator (assign value to variables)
== is the equality operator (binary operator with left sided binding)

Question 2

2 == 2.0

Answer 2

True

Question 3

True or false: comparison operators have higher priority than equality operators

Answer 3

True

Question 4

What is an if statement known as?

Answer 4

Condition statement/instruction

Question 5

What is an if statement within an if statement called?

Answer 5

Nested if statement

Question 6

Explain the difference between if and while

Answer 6

When the condition is met:
- if performs its statements only once
- while repeats the execution as long as the condition evaluates to True

Question 7

What is an endless loop?

Answer 7

An infinite loop is a sequence of instructions in a program which repeat indefinitely

Question 8

What is ‘while number:’ equivalent to?

Answer 8

while number != 0:

Question 9

What is used to exit the loop immediately?

Answer 9

break

Question 10

What is continue used for?

Answer 10

behaves as if the program has suddenly reached the end of the body; the next turn is started and the condition expression is tested immediately.

Question 11

What are the two types of loops in python?

Answer 11

for and while

Question 12

What is and?

Answer 12

a conjunction

(binary operator with lower priority than comparison operators)

Question 13

What is or?

Answer 13

a disjunction

(binary operator with lower priority than and)

Question 14

What are logical operators?

Answer 14

AND and OR

Question 15

What is the unary operator performing a logical negation?

Answer 15

NOT

(same priority are unary +/- (v high))

Question 16

What are the four bitwise operators?

Answer 16

& (ampersand) - bitwise conjunction;
(bar) - bitwise disjunction
~ (tilde) - bitwise negation;
^ (caret) - bitwise exclusive or (xor)

(bar) - bitwise disjunction

Question 17

What do bitwise operators allow you to do?

Answer 17

allow you to manipulate single bits of data

Question 18

True or False:
The arguments for bitwise operators must be integers

Answer 18

True

cannot use floats

Question 19

What is the difference in the operation of the logical and bit operators?

Answer 19

the logical operators do not penetrate into the bit level of its argument. They’re only interested in the final integer value.

Bitwise operators are stricter: they deal with every bit separately.

Question 20

What is a bit mask?

Answer 20

a sequence of zeros and ones, whose task is to grab the value or to change the selected bits

Question 21

What is shifting a value one bit to the left equivalent to?

Answer 21

Multiplying by 2 as 2 is the base for binary numbers

Question 22

What are the shift operators?

Answer 22

&laquo_space;and&raquo_space;

The left argument of these operators is an integer value whose bits are shifted. The right argument determines the size of the shift.

Question 23

What does 17&raquo_space; 1 equal?

Answer 23

17 // 2 (17 floor-divided by 2 to the power of 1) → 8

Question 24

What does 17 &laquo_space;2 equal?

Answer 24

17 * 4 (17 multiplied by 2 to the power of 2) → 68

Question 25

What is the operation of selecting an element from the list known as?

Answer 25

indexing

Question 26

What instruction is used to delete elements from a list?

Answer 26

del

Question 27

If a function is invoke like this result = function(arg), how is a method invoked?

Answer 27

result = data.method(arg)

A method is owned by the data it works for, while a function is owned by the whole code.

Question 28

How would you swap variable 1 with variable 3 in a list?

Answer 28

variable_1, variable_2 = variable_2, variable_1

Question 29

What is the bubble sort method?

Answer 29

we compare the adjacent elements, and by swapping some of them, we achieve our goal.

Question 30

How are lists stored differently to ordinary variables?

Answer 30

the name of an ordinary variable is the name of its content;
the name of a list is the name of a memory location where the list is stored.

The assignment: list_2 = list_1 copies the name of the array, not its contents. In effect, the two names (list_1 and list_2) identify the same location in the computer memory. Modifying one of them affects the other, and vice versa.

Question 31

What is a slice and how do you do it?

Answer 31

A slice is an element of Python syntax that allows you to make a brand new copy of a list, or parts of a list.

It actually copies the list’s contents, not the list’s name.

list_2 = list_1[:]

Question 32

list = [1,2,3,4,5]
list_new = list[1:3]

What is new list?

Answer 32

[2,3]

start is the index of the first element included in the slice;
end is the index of the first element not included in the slice.

Question 33

If the start of the slice specifies an element further from the one described at the end e.g. list[3:1] what will happen?

Answer 33

The list will be empty

Question 34

my_list[0:end] is equal to

Answer 34

my_list[:end]

Question 35

What is the difference between: del mylist and del mylist[:]

Answer 35

the second one deletes the contents of list so mylist will print [] the first one deletes the list variable altogether so mylist will not print and cause an error

Question 36

What does elem in list do?

Answer 36

checks if elem is in list, prints True if it is

(can also used not in)

Question 37

Rewrite this as a list comprehension:
for element in list:
if conditional:
expression

Answer 37

[expression for element in list if conditional]

Question 38

x = [1,2,3,4,5]
print(x[x[2])

What is the output?

Answer 38

x[2] = 3

therefore x[x[2]] = x[3] = 4