Numbers, Strings, Operators

Class objectives

Syntax table

Keyword
description
width(integer)
 Defines the width of the pen. Patameter - integer is a value type of int
if statement
 is a conditional statement.
for statement
 is a loop statement in which operations repeat itself for a limited amount of time

Number

What is Number?

Numbers in Python are the same as the numbers you have learnt in math class. We have four mathmatical operators.

How to define a number variable?

# num is the name, 17 is the value, = means assign value 17 to variable num
num = 17
print(num)

How to define multiple number variables?

# num01, num02 and num03 are the names. 23, 46 and 78 are the values, = means assign values 23, 46 and 78 to variables num01, num02 and num03.
num01, num02, num03 = 23, 46, 78
print(num01, num02, num03)

Operators

  • addition +
  • subtraction -
  • multiplication *
  • division /
  • floor division //
  • remainder %
  • assign sign =
  • equal sign ==
num01, num02, num03 = 23, 46, 78
add = num01 + num02
sub = num02 - num01
mul = num01 * mul03
divi = num02 / num01
print('Addition: ' + int(add))
print('subtraction: ' + int(sub))
print('Multiplication: ' + int(mul))
print('Division: ' + int(divi))

String

What is String?

String is the text we print in console or in turtle screen.

How to define a String variable?

# string is the name, 'Hello, Python' is the value, = means assign value 'Hello, Python' to variable string
string = 'Hello, Python'
print(string)

How to define multiple String variables?

# string01, string02 and string03 are the names. 'My name', " is", ' Alim' and '7' are the values, = means assign values 'My name', " is", ' Alim' and '7' to variables string01, string02 and num03.
string01, string02, string03, string04 = 'My name', " is", ' Alim', '7'
print(string01, string02, string03, string04)

string01, string02, string03, string04 = 'My name', " is", ' Alim', '7'
print(string01 + string02 + string03)

How to convert a number to string and back?

For example: 'Addition: ' and add are different data types. In Python, unable to add two different data types unless one of which is converted to the type of another. int() is a Python function converts String to Number. str() is a Python function converts Number to String.

Practice them in turtle

How to print a String in turtle?

We need write() function to print a String in turtle. For example:

from turtle import *

write("Python is fun!", align='center', font=('Arial', 38, 'bold'))

How to practice Number in turtle?

It’s easy to do a calculation and present the result on turtle screen. For example:

write("{0} + {1} = {2}".format(5, 7, 5 + 7), align="center", font=("Arial", 48, "bold"))
penup()
goto(0, 200)
write("{0} - {1} = {2}".format(5, 7, 5 - 7), align="center", font=("Arial", 48, "bold"))
penup()
goto(0, 100)
write("{0} * {1} = {2}".format(5, 7, 5 * 7), align="center", font=("Arial", 48, "bold"))
penup()
goto(0, -100)
write("{0} / {1} = {2}".format(5, 7, 5 / 7), align="center", font=("Arial", 48, "bold"))
penup()
goto(0, -200)
write("{0} // {1} = {2}".format(5, 7, 5 // 7), align="center", font=("Arial", 48, "bold"))
penup()
goto(0, -300)
done()

How to practice List in turtle?

Assume we have random colors in a list, paint each shape in a different color. For example:

square = 4
triangle = 3
red, green, yellow = 'red', 'green', 'yellow'

# Following is how to define a function
# def is a suffix indicates define a function. draw is the name of function. sides is the parameter. We'll talk about more details in following classes.
def draw(sides):
	width(30)
	if sides == square:
		color(green)
	elif sides == triangle:
		color(yellow)
	for each_side in range(sides):
		forward(100)
		right(360/sides)
	done()

# Following is how to call a function
draw(4)

if draw(4)

if draw(3)

Homework: Draw shapes in different color

Input

Given a function with a parameter of sides. If sides is even, draw the shape in red color. If sides is odd, draw the shape in green color.

For example

def draw_even_odd(sides):

Output

if draw_even_odd(8)

if draw_even_odd(5)