Programming in Python

Question 1

Display data on screen

Answer 1

print ( )

Some examples:
print (“HelloWorld”)
print (“Name: “, name)
print (“5 + 3 = “, 5+3)
print (“Hello”, name, “welcome home”)

Question 2

Input data from keyboard

Answer 2

input()

Some examples:
name = input()
name = input (“Enter name: “)
age = int(input(“Enter age: “))
cost = float(input(“Enter price: “))

Question 3

Conditional statement

Answer 3

if <condition>:
<statements></statements></condition>

if <condition>:
<statements>
else:
<statements></statements></statements></condition>

Question 4

Nested ifs

Answer 4

if <condition 1>:
<statements>
elif <condition 2>:
<statements>
elif <condition 3>:
<statements>
...
else:
<statements></statements></statements></statements></statements>

Question 5

Fixed Loop

Answer 5

for <variable> in range (<start>, <end value + 1>):
<statements></statements></start></variable>

Examples:

for x in range (0, 10):
print (“Enter name: “)
name[x] = input()

for count in range (1, 21):
print (count)

Question 6

Conditional Loop

Answer 6

while <condition>:
<statements></statements></condition>

Examples:

while password != “1234”:
print (“Incorrect password. Please try again.”)
password = input()

while choice != 3:
print (“Main Menu”)
print (“1. Input Data”)
print (“2. Display Data”)
print (“3. Exit”)
choice = int(input(“Please enter your option: “))

Question 7

Creating an Array

Answer 7

Creating / Declaring an array:

<array> = [<data>] * <number>

Examples:

name = [""]*10

score = [0]*25

distanceArray = [0.0]*100

SubscriptionArray = [False]*200

You can also ask the user how many locations they want in the array and use that information to create the array, for example:

numOfLocations = int(input("How many people would you like to register? "))
name = [""] * numOfLocations
</number></data></array>

Question 8

Writing to an Array

Answer 8

Normally to be efficient we use a for loop to read and write to and from an array.

To write to an array:

for <variable> in range (0, <number>):
<array> [<variable>] = input ("<message>")</message></variable></array></number></variable>

For example:

for x in range (0, 10):
name[x] = input (“Enter name: “)

for count in range (0, 25):
score[count] = int(input(“Enter score: “))

for c in range (0,100):
distanceArray[c] = float(input(“Enter distance for participant “, c+1, “: “))

Question 9

Reading from an Array

Answer 9

Same as when writing to an array, to read efficiently from an array we need to use a for loop so something as follows:

for <variable> in range (0, <number>):
print (<array> [<variable>])</variable></array></number></variable>

Some examples:

for x in range (0,10):
print (name[x])

for count in range (0,25):
print (“Score for student”, count+1, “: “, score[count])

for c in range (0,100):
print (“Participant”, c+1, “: “, distanceArray[c])

Question 10

What are Parallel Arrays?

Answer 10

Parallel arrays are just a number of arrays that have the same number of locations and are used together to store different details about the same object/s or people.

For example, to store the name, surname, age and class of 25 students you would have the following arrays that work in parallel:

name = [””]25
surname = [””]25
age = [0]25
class = [””]25

Question 11

Declaring Parallel Arrays

Answer 11

To declare parallel arrays, it is the same as declaring a single array, but you will have more than one array to declare.

For example:

name = [””]25
surname = [””]25
age = [0]25
class = [””]25

You can also ask the user how many locations you need in the arrays, so for example:

numberOfPets = int(input(“How many pets would you like to register?”))
petName = [””] * numberOfPets
type = [””] * numberOfPets
breed = [””] * numberOfPets
age = [0] * numberOfPets
ownerID = [0] * numberOfPets

Question 12

What is modular programming?

Answer 12

Using modules to write code in easily manageable chunks that can be reused. Modules in Python can be either procedures or functions.

Question 13

What is the difference between a function and a procedure?

Answer 13

A function returns a value back to the main program. A procedure does not.

Question 14

How do you write a Procedure in Python?

Answer 14

At the top of the page, above the main program, write:

def <procedure> (<parameters>):
<statements></statements></parameters></procedure>

Examples:

def displayData (array):
for x in (0, len(array)):
print (“Name: “, name[x])

def calculateCakeCircumference (diameter):
pi = 3.142
circumference = pi * diameter
print (“Cake circumference is “, circumference)

Question 15

How do you write a Function in Python?

Answer 15

At the top of the page, above the main program, write:

def <function> (<parameters>):
<statements></statements></parameters></function>

Examples:

def calculateCakeCircumference (diameter):
pi = 3.142
circumference = pi * diameter
return circumference

def inputNames ():
for x in range (0, 100):
name[x] = input (“Enter name: “)
return name

Question 16

How to call a procedure from the main program.

Answer 16

You simply write the name of the procedure…

<procedure> (<any>)

Examples:

displayData (nameArray)

calculateCakeCircumference (size)

inputDetails()
</any></procedure>

Question 17

How to call a function from the main program.

Answer 17

You need to store the value returned by that function into a variable, since functions are returning a value to the main program.

Example:

ribbonLength = calculateCakeCircumference (size)

area = calculateArea (length, breadth)

nameArray = inputNames()

Question 18

What is a predefined function?

Answer 18

A function that has been created and stored in a library and can be used in your program to carry out a specific process that you do not need to code yourself.

Question 19

Which are the four predefined functions covered in Higher computing?

Answer 19

split() - used to Create Substrings (i.e. to divide strings into smaller strings)
chr() - used to convert an ASCII value into a character
ord() - used to convert a character into its ASCII value
int() - used to convert floating point numbers to integer
% - modulus - returns the remainder part of a division

Question 20

What is a record?

Answer 20

A record is a collection of information about one object. It is very similar to a record in a database table.

Question 21

Declaring a record

Answer 21

from collections import namedtuple

<record> = namedtuple ("<record>", "<field name 1> <field name 2> <field name 3> ... ")

Example:

from collections import namedtuple

Person = namedtuple ("Person", "name surname age address height weight")
</record></record>

Question 22

Creating an instance of a record (saving details in
a record)

Answer 22

<variable> = <record> (<details>)

Example:

patient1 = Person ("Matthew", 26, "12 Main Street", 184.4, 81.3)
</details></record></variable>

Question 23

Displaying data from a record

Answer 23

print (<variable>.<field>)</field></variable>

Examples:
print (patient1.name)

print (“Patient name: “, patient1.name, patient1.surname, “\n”, “Age: “, patient1.age, “\n”, “Height: “, patient1.height, “\n”, “Weight: “, patient1.weight)

Question 24

Which are the four steps to declaring an Array of Records

Answer 24

This is a combination of arrays and records

Three steps:
1. Import namedtuple
2. Create a record
3. Create an empty instance of the record
4. Create an array with the empty instance of the record as its data type

Example:
from collections import namedtuple

Person = namedtuple (“Person”, “name surname age address height weight”)
emptyPerson = Person (“”, “”, 0, “”, 0.0, 0.0)
arrayOfPerson = [emptyPerson]*100

Question 25

Inserting data into an array of records

Answer 25

Use a fixed loop to input as many records as needed. This is very similar to inserting data into a parallel array with only slight changes.

Question 26

How to insert data into an array of records

Answer 26

for <counter> in range (0, <array>):
<variable1> = input(<message>)
...</message></variable1></array></counter>

  <array of record name> [<counter>] = <name of record> (<variable1>, <variable2>, ...)

Example:

for count in range (0, 100):
name = input (“Enter name: “)
surname = input (“Enter surname: “)
age = int (input (“Enter age: “))
address = input (“Enter address: “)
height = float (input (“Enter height: “))
weight = float (input (“Enter weight: “))

  arrayOfPerson [count] = (name, surname, age, address, height, weight)

Question 27

What are the three steps to follow when reading from or writing to a file?

Answer 27

Open file
Read / Write data
Close file

Question 28

How do you open a text or csv file when you are writing to it?

Answer 28

If you want to replace anything that already exists in the file and start over, you use “w” for write:

<variable> = open ("<file>, "w")

Examples:
file = open ("fileName.csv", "w")
textFile = open ("fileName.txt", "w")

If you want to add the data to what already exists in the file without replacing it, you use "a" for append:

<variable> = open ("<file>, "a")

Examples:
file = open ("fileName.csv", "a")
textFile = open ("fileName.txt", "a")
</file></variable></file></variable>

Question 29

How do you open a file to read from it?

Answer 29

<variable> = open ("<file>, "r")

Examples:
file = open ("fileName.csv", "r")
textFile = open ("fileName.txt", "r")
</file></variable>

Question 30

How do you close a file?

Answer 30

<variable>.close()

Examples:
file.close()
textFile.close()
</variable>

Question 31

What are the steps to write data to a text file?

Answer 31

Step 1: This is optional and only necessary if you have data that needs to be concatenated. Concatenate all data into one variable.

Step 2: Write the data into the file.

Question 32

How do you write data into a text file?

Answer 32

<variable> = <data part 1> + <data part 2> ...
<file>.write (<variable>)

Example:

fileData = name + " " + surname + "\n"
file.write (fileData)
</variable></file></variable>

Question 33

How do you write data into a csv file?

Answer 33

When writing into a csv file, you need to make sure that you separate each cell content by a comma (,) and each record by a new line (\n).

Same two steps as when writing into a text file are needed, i.e.:

Step 1: concatenate all data into one variable
Step 2: write the contents of the variable into the file

<variable> = <data 1> + "," + <data 2> + ... + "\n"
<file>.write (variable)

Example:
for x in range (0,100):
fileData = arrayOfPerson[x].name + "," + arrayOfPerson[x].surname + "," + arrayOfPerson[x].age + "," + arrayOfPerson[x].address + "," + arrayOfPerson[x].height + "," + arrayOfPerson[x].weight + "\n"
file.write(fileData)
</file></variable>

Question 34

How do you read data from a text file?

Answer 34

<variable> = file.read()

Example:
fileData = file.read()

You might need to split the data depending on how it is stored in the file.
</variable>

Question 35

How do you read data from a csv file?

Answer 35

<variable> = file.read()
<variable2> = <variable>.split ("\n")
for <counter> in range (0, len(<variable2>-1):
<variable3> = <variable2>[<counter>].split(",")
<data variable 1> = <variable3>[0]
<data variable 1> = <variable3>[0]
...

Example - storing data into parallel arrays:
fileData = file.read()
separateRecords = fileData.split("\n")
for x in range (0, len(recordData)-1):
recordData = separateRecords[x].split(",")
name[x] = recordData[0]
surname[x] = recordData[1]
age[x] = int(recordData[2])
...

Example - storing data into an array of records:
fileData = file.read()
separateRecords = fileData.split("\n")
for x in range (0, len(recordData)-1):
recordData = separateRecords[x].split(",")
name = recordData[0]
surname = recordData[1]
age = int(recordData[2])
...
arrayOfPeople[x] = Person (name, surname, age, ...)
</variable3></variable3></counter></variable2></variable3></variable2></counter></variable></variable2></variable>