# Python Key Skills

## Table of Contents

- 1. Python Key Skills
- Learn It - convert from number data type to string
- Learn It - comparing values and comparators
- Learn It - create an array of numbers or strings
- Learn It - array index and get an item from an array
- Learn It - swap the positions of two items in an array
- Learn It - generate random numbers
- Learn It - Find out of a number is a mulitple of other number

## 1 Python Key Skills

### Learn It - convert from number data type to string

myName = "Jack" # A string myAge = 5 # A number # To convert myAge to a string so we can make a longer string to display: print(myName + " : " + str(myAge))

### Learn It - comparing values and comparators

- Comparators check if a value is (or is not) equal to, greater than (or equal to), or less than (or equal to) another value.
- The result of comparator operation is always a Boolean vale -
`True`

or`False`

- Depending on the comparing outcome, the program then decide what to do next.
- Python has the following comparators:
- logical operators
- Equality, ==
- Not equal, !=
- Greater Than, >
- Less Than, <
- Greater than or equal to, >=
- Less than or equal to, <=

- Boolean operators: and, or, not
`and`

: evaluates to True when both clauses (expressions) are True`or`

: evaluates to True when either of the expressions are True`not`

: evaluates to True when the expression is False. Evaluates to False when the expression is True.

- logical operators
- Example usages of comparators

hunger = True numberOfPizza = 5 drink="fizzyPop" if numberOfPizza >= 3: print("Have some pizza, since we have 3 or more") else: print("You cannot have any pizza") if hunger == True and numberOfPizza >= 1: print("You are hungry, and there is at least one pizza") else: print("Either you are not hungry or the food is not pizza") if not drink == "fizzyPop": print("No drink for me.") #The above is same as: if drink != "fizzyPop": print("No drink for me.")

### Learn It - create an array of numbers or strings

# An array of numbers testScores = [98, 78, 65, 89, 75] # An array of strings names = ['Jack', 'Kerry', 'Julia', 'Matthew', 'David']

### Learn It - array index and get an item from an array

- Each individual data pieces is called an item
- Each item has a position number called
`index`

- For the following array, names, "Jack" is at index 0.
- To get "Jack", you use
`names[0]`

# An array of strings names = ['Jack', 'Kerry', 'Julia', 'Matthew', 'David']

### Learn It - swap the positions of two items in an array

- Swap the position of "Jack" with "Julia"
- Method 1: use a temporary variable
names = ['Jack', 'Kerry', 'Julia', 'Matthew', 'David'] temp = names[0] names[0] = names[2] names[2] = temp

- Method 2: in place swap
names = ['Jack', 'Kerry', 'Julia', 'Matthew', 'David'] names[0],names[2] = names[2],names[0]

- Method 1: use a temporary variable

### Learn It - generate random numbers

- In Python, to generate random numbers, you use a module call
**random** - At the start of your program/code, you need to import the module
**random**- exmaple 1: generate a random whole number from 0 up to a limit
import random randomNumber = random.randrange(100) # The above code picks a random number between 0 and 99 randomNumber = random.randrange(2, 10, 2) # The above code picks a random number from 2, 4, 6, 8 (goes up by 2)

- exmaple 2: generate a random number between a range
import random randomNumber = random.randint(1, 100) # The above code picks a random whole number between 1 and 100 randomNumber = random.randint(50, 100) # The above code picks a random whole number between 50 and 100

- example 3: pick a random item from a list
import random names = ['Jack', 'Kerry', 'Julia', 'Matthew', 'David'] randomIndex = random.randrange(len(names)) print("The random picked name is: ", names[randomIndex])

- exmaple 1: generate a random whole number from 0 up to a limit

### Learn It - Find out of a number is a mulitple of other number

- In maths, we know that if a number A is a multiple of number B, it means A/B will not have a remainder - the remainder is 0.
- In Python, there is an operator for computing remainder conveniently. The operator is called
`modulo`

which is`%`

- Example 1

A=40 B=5 A%B will output 0

- Example 2

A = 12 B= 9 A%B will output 3 since 12 only contains one 9, the remainder is 12- 1 x 9=3

- Example 3

A = 9 B= 12 A%B will output 9 since 9 contains zero 12, the remainder is 9 - 0 x 12 = 9

- This remainder operator can be used to check if a number is even or odd

num = int(input("Give me a number: ")) if num % 2 == 0: print("It's an even number") else: print("Not an even number")