Python Notes

Question 1

Is python case sensitive and does spacing matter?

Answer 1

yes to both

Question 2

What is Print used for?

Answer 2

To show a value

Question 3

Arithmatic in python?

Answer 3

+, -. *, /

Addition, subtraction, multiplication, division

Question 4

**?

Answer 4

Does number to the power of a other

Question 5

what does % do?

Answer 5

Gives remainder from a division

Question 6

//?

Answer 6

Divides one number by another but rounds down to nearest integer

(still rounds down even when negative)

Question 7

how to assign closely related variables?

Answer 7

x, y, z = 2, 3, 4

Question 8

Can you have spaces in variable names?

Answer 8

no, should use underscores and all lower case

Question 9

what is += used for?

Answer 9

Telling a descriptive value it is being effected by new values

also -= when want to subtract values

Question 10

Float?

Answer 10

Decimal answer (even if it .0

Question 11

Int?

Answer 11

Integer (whole number)

Question 12

How to find out if int or float?

Answer 12

Use type()

Question 13

Interaction with an int and a float always =?

Answer 13

Float

Can also use int and float as functions to add or remove decimal points

x = int(4.7) # x is now an integer 4
y = float(4) # y is now a float of 4.0

Question 14

What does bool (boolean) do?

Answer 14

Say if something is true or false

Question 15

Comparison operators?

Answer 15

< less than
> greater than
<= less or equal than
>= greater or equal than
== equal to
!= not equal to

Question 16

What is a string?

Answer 16

Data type for immutable ordered sequences of characters

Question 17

How to print words?

Answer 17

Use Print (“…….”)

Question 18

How to get rid of issue of using speech marks within a quote?

Answer 18

Use single for overall one, and use double for quote

If need more than one, use a / before the ‘ to let python know its part of the string

Question 19

How to combine, or repeat strings or put a space?

Answer 19

+ for combine

• for repeat

” “ for space

Question 20

what does Len( ) do?

Answer 20

Returns the length of a string

Question 21

How to convert values into a string value?

Answer 21

str()

Question 22

How to convert values into a integer?

Answer 22

Int()

Question 23

What is a method?

Answer 23

A function that belongs to an object

for example title() will turn the string into a title so capitals in each words

Is placed in the bracket and doesn’t need anything in its own brackets, acts on the string

Question 24

What is the length of the string variable verse?
What is the index of the first occurrence of the word ‘and’ in verse?
What is the index of the last occurrence of the word ‘you’ in verse?
What is the count of occurrences of the word ‘you’ in the verse?

Answer 24

length = len(verse)
print(length)

index = verse.index(“and”)
print(index)
rindex = verse.rindex(“you”)
print(rindex)

count = verse.count(“you”)
print(count)

Question 25

Example of a list and how to access parts of the list?

Answer 25

months = [‘January’, ‘February’, ‘March’, ‘April’, ‘May’, ‘June’, ‘July’, ‘August’, ‘September’, ‘October’, ‘November’, ‘December’]

print(months[0]) # January
print(months[1]) # February
print(months[7]) # August
print(months[-1]) # December
print(months[25]) # IndexError: list index out of range

Question 26

How would you get the Q3 months (slicing)

Answer 26

months = [‘January’, ‘February’, ‘March’, ‘April’, ‘May’, ‘June’, ‘July’, ‘August’, ‘September’, ‘October’, ‘November’, ‘December’]

q3 = months[6:9]
print(q3) # [ ‘July’, ‘August’, ‘September’]

Note how the lower bound is inclusive, but the upper bound is exclusive

Note it starts from 0, not 1

Question 27

What do ‘in’ and ‘not in’ do?

Answer 27

evaluates if the object on the left hand side is in, or not in the object on the right eg.

eg . print( ‘Sunday’ in months, ‘Sunday’ not in months)

Gives False True

Question 28

Difference between strings and lists?

Answer 28

Mutability is whether an object can change its values once it has been created

Lists are mutable (can be changed)

Strings are immutable (can’t be changed)

Question 29

What is ordering and are lists and strings ordered?

Answer 29

When order of elements within a list matter

Yes both strings and lists are ordered

Question 30

Use list indexing to determine how many days are in a particular month based on the integer variable month, and store that value in the integer variable num_days. For example, if month is 8, num_days should be set to 31, since the eighth month, August, has 31 days.

Answer 30

month = 8
days_in_month = [31,28,31,30,31,30,31,31,30,31,30,31]

num_days = days_in_month[month - 1]
print(num_days)

Question 31

what does max() do when used on a list or string?

Answer 31

Gives the largest value

Value that would appear last if ordered alphabetically

Question 32

What does min() do?

Answer 32

Opposite of max

Question 33

What does sorted() do?

Answer 33

Returns a copy of a list ordered from smallest to largest, leaving the original unchanged

can do the opposite argument by adding into the function ,reverse=true

Question 34

How to separate all the words out in a list on separate lines?

Answer 34

“/n”.join

if want hypothons between the words use “-“ .join

Question 35

Difference between data types and data structures?

Answer 35

A data type is just a type that classifies data. This can include primitive (basic) data types like integers, booleans, and strings, as well as data structures, such as lists.

Data structures are containers that organize and group data types together in different ways. For example, some of the elements that a list can contain are integers, strings, and even other lists!

Question 36

What is a tuple?

Answer 36

A data type for immutable ordered sequences of elements

Used when have values that are so closely related will always be used together, eg longitude and latitude

Question 37

Example of a tuple?

Answer 37

dimensions = 52, 40, 100
length, width, height = dimensions
print(“The dimensions are {} x {} x {}”.format(length, width, height))

Question 38

What are sets?

Answer 38

A data type for mutable unordered collections of unique elements

eg. amount of people visiting your website and you collect all the countries it has been from, there will be duplicates

Question 39

How do you remove duplicates?

Answer 39

Use the set() function

countries = [‘Angola’, ‘Maldives’, ‘India’, ‘United States’, ‘India’, ‘Denmark’, ‘Sweden’, ‘Ghana’, … 777 more countries not displayed]
print(len(countries)) # 785
print(countries[:5]) # [‘Angola’, ‘Maldives’, ‘India’, ‘United States’, ‘India’]
country_set = set(countries)
print(country_set) = 196

Question 40

What does the add() and pop() methods do?

Answer 40

You can add elements to sets using the add method, and remove elements using the pop method, similar to lists. Although, when you pop an element from a set, a random element is removed. Remember that sets, unlike lists, are unordered so there is no “last element”.

Question 41

Whats a dictionary?

Answer 41

A data type for mutable objects that store mappings of unique keys to values

eg. elements = {“hydrogen”: 1, “helium”: 2, “carbon”: 6}

Question 42

What does get() do?

Answer 42

Sees if value is in a dictionary, gives true or false

Question 43

Example of identity operators?

Answer 43

is evaluates if both sides have the same identity

is not - evaluates if both sides have different identities

Question 44

Example of a compound data structure, what does it add to the elements table?

Answer 44

elements = {“hydrogen”: {“number”: 1,
“weight”: 1.00794,
“symbol”: “H”},
“helium”: {“number”: 2,
“weight”: 4.002602,
“symbol”: “He”}}

Question 45

How do you do a lookup in a compound data structure?

Answer 45

helium = elements[“helium”] # get the helium dictionary
hydrogen_weight = elements[“hydrogen”][“weight”] # get hydrogen’s weight

Question 46

How do you add to a compound data structure?

Answer 46

oxygen = {“number”:8,”weight”:15.999,”symbol”:”O”} # create a new oxygen dictionary
elements[“oxygen”] = oxygen # assign ‘oxygen’ as a key to the elements dictionary
print(‘elements = ‘, elements)

Question 47

How do you split a verse into a list of words?

Answer 47

verse_split = verse.split()

Question 48

How do you turn a list of words into a data structure that stores unique elements?

Answer 48

verse_set = set(verse_list)

Question 49

How do you count the amount of words in a unique data structure?

Answer 49

num_unique = len(verse_set)

Question 50

How do you find if a certain word is in the dictionary?

Answer 50

contains_breathe = if ‘breathe’ in verse_dict:
print(“The word ‘breathe’ is in the dictionary.”)
else:
print(“The word ‘breathe’ is not in the dictionary.”)
print(contains_breathe)

Question 51

How do you find the unique number of keys in a dictionary?

Answer 51

num_keys = len(verse_dict.keys())
print(num_keys)

Question 52

How do you create and sort a list of dictionary keys?

Answer 52

sorted_keys = sorted(verse_dict.keys())

Question 53

How do you find the first element in the dictionary keys?

Answer 53

first_key = sorted_keys[0]
print(first_key)

Question 54

How do you find the element with the highest value in the list of keys?

Answer 54

key_with_highest_value = max(verse_dict, key=verse_dict.get)
print(key_with_highest_value)

Question 55

Features of a list?

Answer 55

Ordered

Mutable

[ ] or list() - are its constructors

eg. [5.7, 4, ‘yes’, 5.7]

Question 56

Features of a tuple?

Answer 56

Ordered

Not Mutable

( ) or tuple() are its constructors

eg. (5.7, 4, ‘yes’, 5.7)

Question 57

Features of a set?

Answer 57

Not ordered

Mutable

{}* or set() are its constructors

eg. {5.7, 4, ‘yes’}

Question 58

Features of a dictionary?

Answer 58

Not ordered

Not mutable

{ } or dict() are its constructors

eg. {‘Jun’: 75, ‘Jul’: 89}