Chapter 4: Data Types in Python

Question 1

What are integers in Python, and how do you declare them?

Answer 1

Integers are numbers with no decimals such as -4,4. The declare an integer write variableNAme= initial value.
userAge=30

Question 2

What is float and how do you declare it?

Answer 2

It refers to numbers that have decimal parts such as 1.234, -0.089. To declare a float in Python we write variableNAme = initial value
Example userHeight = 157.6

Question 3

What is a string? How do you declare it?

Answer 3

It refers to text. To declare it you can either use variableName= 'initial value'(single quotes) or variableName="initial value"(double quotes
example
userName="Amy"
userSpouseName = "Eric"
userAge = "33"

Here 33 isn’t an integer but a string as it is encased in quotes.

Question 4

How can you combine multiple substrings? Provide examples

Answer 4

Using the concatenate”+” sign. For example, “Amy” + “Eric” will give us Amy Eric

Question 5

What are built-in string functions?

Answer 5

Python includes a number of built-in functions to manipulate strings. A function is a block of reusable code that performs a certain task.

Question 6

Provide examples of built-in string functions

Answer 6

upper() method which can be used to capitalize all the letters in a string. For example, ‘Amy’.upper() will give us the string ‘AMY’.

Question 7

What is the syntax for the % operator?

Answer 7

“string to be formatted”%(values or variables to be inserted into string, separated by commas)

Question 8

What are the three parts to the % operator?

Answer 8

First, we write the string to be formatted in quotes.
Next, we write the % symbol.
Finally, we have a pair of parentheses within which we write the values or variables to be inserted into the string. The parentheses are known as tuple.

Question 9

What will be the output for the below code?
brand = “Apple”
exchangeRate = 1.2345
message= “The price of this %s laptop is %d USD and the exchange rate is %4.2fUSD to 1 EUR”%(brand,1299,exchangeRate)
print(message)

Answer 9

The price of this Apple laptop is 1299 USD and the exchange rare is 1.23 USD to 1 EUR

Question 10

What are %s, %d and %4.2f?

Answer 10

They are known as formatters and serve as placeholders in the string.
%s represents the string
%d represents an integer. to add space before the integer, add a number between % and d sign i.e. %5d adds 2 spaces in front with total length being 5.
%4.2f represents the float. in 4.2, 4 refers to the total length and 2 refers to the decimal places. To add space before the number increase the total length i.e. 4.2 to 7.2

Question 11

What is the syntax for format () method?

Answer 11

“string to be formatted”.format()

Question 12

Provide and explain an example of the format () method.

Answer 12

message=”The price of this {0:s} laptop is {1:d} USD and the exchange rate is {2:4.2f} USD to 1 EUR”.format(“Apple”, 1299, 1.235)
WE use braces in the format method. 0:s is assigning the position to the string i.e. Apple, 1:d is assigning the position 1 to the integer 1299 and {2:4.2f} is assigning the second position with 4 as total length and 2 decimal places to the float 1.235. Now if you write a second message with the positions swiped as in
message1=”The price of this {1} laptop is {0} USD and the exchange rate is {2} USD to 1 EUR”.format(“Apple”, 1299, 1.235)
the result will be:
The price of this 1299 laptop is Apple USD and the exchange rate is 1.23 USD to 1 EUR.

Question 13

What if you don’t want to format the string?

Answer 13

You can simply write
message=”The price of this {} laptop is {} USD and the exchange rate is {} USD to 1 EUR”.format (“Apple”, 1299, 1.235).
The output will be:
The price of this Apple laptop is 1299 USD and the exchange rate is 1.235 USD to 1 EUR

Python assigns the position in the order the variables are mentioned in the parentheses. Therefore, if you change the order to (1299, “Apple”, 1.235), the output will be:
The price of this 1299 laptop is Apple USD and the exchange rate is 1.235 USD to 1 EUR

Question 14

For the format method where does the position start from?

Answer 14

ZERO

Question 15

What will the below code yield?

message3=’ and {:d}.format{1.23, 12}

Answer 15

6spaces1.23 and 12

Question 16

What will the below code yield?

message4=”{}.format(1.23)

Answer 16

1.23

Question 17

What is Type Casting?

Answer 17

Changing the format of the data types from integer to float to String is called type casting

Question 18

What are the three built-in functions that allow us to do type casting?

Answer 18

Int(), Float(), Str()

Question 19

What does INT() do?

Answer 19

It converts float and an appropriate string to Integer. For example, INT(2.34) will yield 2, INT(“2”) it will yield 2

Question 20

What does float() do?

Answer 20

It converts integer and appropriate string to float. For example, float(2) or float (“2”), we will get 2.0

Question 21

What does str() do?

Answer 21

It converts a float or integer to a string. For example, str(2.1) will yield “2.1”

Question 22

What is a list?

Answer 22

It refers to collection of data that is related. Instead of storing this data separately, we can store them as a list.

Question 23

How do you declare a list?

Answer 23

listName=[initial values]

For example, userAge=[21,22,23,24,25]

Question 24

What kind of brackets are used to store a list?

Answer 24

Square brackets

Question 25

How do you declare an empty list and which function is used to add items to it?

Answer 25

userAge=[]

We use append() function to add items to this list

Question 26

What are indexes?

Answer 26

The individual values in the list are assigned an index number. The first item on the list is always indexed 0 and the last as -1. For example, in userAge = [21,22,23,24,25],
userAge[0] = 21
userAge[1] = 22
userAge[-1] = 25

Question 27

How do you assign the complete or a part of the list to a variable? The list being
userAge = [21,22,23,24,25]

Answer 27

userAge2=userAge
This will assign all the values in userAge list to the variable userAge2. For partial assignment, wuserAge3=userAge[2:4] will yield [23,24]. 2 represents the index number in the list, 4 actually means 4-1 i.e. up until the item with index number 3.

Question 28

What is the notation [2:4] called(taking cue from the previous card), and what is a stepper? Explain.

Answer 28

The notation 2:4 is a slice, and the third number in this notation is called a stepper. If we write userAge4= userAge [1:5:2], we get a sub list for every second item from index 1 to index 5-1. Therefore, if the list is userAge= [21,22,23,24,25] then the result would be userAge4= [22,24]

Question 29

What are the defaults for the slice notations?

Answer 29

The default for the first number is 0. Therefore, userAge[:4] will yield values from index 0 to index 4-1.

The default for second number is the size of the list. Therefore, userAge[1:] will yield values from index 1 to 5-1 (assuming the size of the list is 5 items)

Question 30

How do you modify the items in the list?

Answer 30

listName[index of item to be modified]= new value
For example
userAge[1]=5 yields
userAge=[21,5,23,24,25]

Question 31

Which function do you use to add items to the list and how?

Answer 31

append()
For example
userAge.append(99) will add the number 99 to the end of the list. The list is now userAge=[21,5,23,24,25,99]

Question 32

Which function do you use to delete the items from the list and how?

Answer 32

del listName[index of the item to be deleted].
For example, del userAge[2 it will yield
userAge=[21,4,24,25,99]

Question 33

What would be the syntax for printing the third item from the list if the list is myList=[1,2,3,4,5,”Hello”]?

Answer 33

print(myList[2]) will yield 3

Question 34

print the last item

Answer 34

print(myList[-1])

Question 35

assign myList (from index 1 to 4) to myList2 and print myList2

Answer 35

myList2=myList[1:5]

print(myList2)

Question 36

modify the second item in myList and print the updated list

Answer 36

myList[1]=22

print(myList)

Question 37

append a new item to the list and print the updated list

Answer 37

myList.append(“How are you?”)

print(myList)

Question 38

remove the sixth item from myList and print the updated list

Answer 38

del myList[-1] or del myList[5]

print(myList)

Question 39

What is a Tuple?

Answer 39

Tuple is another form of a list where the initial values are fixed and cannot be modified throughout the program.

Question 40

Give an example of a Tuple.

Answer 40

MonthsOfYear= (“Jan”,”Feb”,”Mar”,”Apr”,”May”,”June”,”July”,”Aug”,”Sept”,”Oct”,”Nov”,”Dec”)

Unlike a list, Tuple uses parentheses to define its values.

Question 41

How do you modify the values in a Tuple?

Answer 41

MonthsOfYear[0]=”Jan”

MonthsOfYear[-1]=”Dec”

Question 42

What is a dictionary?

Answer 42

It is a collection of related data PAIRS.

For example, if we want to store the username and their respective age, we can use dictionary for that

Question 43

How do you declare a dictionary?

Answer 43

dictionaryName= {dictionary key:Data}
For example,
userNameAndAge={“Peter”:38, “John”:51, “Alex”:13, “Alvin”:NA}
The keys have to be unique and can’t be repeated. The name Peter can’t appear twice in the dictionary

Question 44

What is an alternate method of declaring the dictionary?

Answer 44

Using the dict() method
userNameAndAge=dict(Peter=38,John=51,Alex=13,Alvin=NA)
We use parantheses and quotes aren’t need for defining the items.

Question 45

How do you access the individual items in a dictionary?

Answer 45

to get John’s age you write

userNameAndAge[“John”] it will yield 51

Question 46

How do you modify the items in a dictionary? Explain with an example

Answer 46

dictionaryName[dictionary key of item to be modified]= new data.
For example:
to modify “John”:51 we write
userNameAndAge[“John”]=21 , this will yield
userNameAndAge=dict(Peter = 38, John=21,Alex=13, Alvi= NA)

Question 47

What is the syntax for declaring a dictionary with no items in it?

Answer 47

dictionaryName=dict() or dictionaryName={}

Question 48

adding items to the empty dictionary at the end

Answer 48

userNameAndAge[“Joe”]=40

Question 49

removing items from the dictionary

Answer 49

del dictionaryName[dictionary key]

del userNameAndAge[“Alex”]

Question 50

Running a program with dictionaries. Dictionary can contain different kinds of data types
#declaring a dictionary

Answer 50

myDict={“One”:1.35, 2.5:”Two Point Five”, 3:”+”, 7.9:2}

Question 51

Are items in a dictionary in the same order as the way you declared them?

Answer 51

No, they are not. That’s why perhaps they don’t have index numbers.

Question 52

print the item with key=”One”

Answer 52

print(myDict[“One”]

Question 53

print the item with key =7.9

Answer 53

print(myDict[7.9])

Question 54

modify the item with key=2.5 and print the updated list

Answer 54

myDict[2.5]=”Two and a half”

print(myDict)

Question 55

add a new item and print the updated dictionary

Answer 55

myDict[“New Item”]=”I’m new”

print(myDict)

Question 56

remove the item with key= “One”and print the updated dictionary

Answer 56

del myDict[“One”]

print(myDict)