while True:
    print('You are nice!')
    answer = input('Should I stop saying that? Write yes in that case.')
    if answer == 'yes':
        break
            

i = 0
while i < 100: 
    if i % 2 == 0: # continue with the next repetition if i is divisible by 2
        continue
    print(i,'is an odd number')
            

temp = int(input('What is the temperature?'))
if temp > 20:
    print('Warm and nice!')
elif temp > 0: #if temp <= 20 and temp > 0
    print('Not very cold, but not so warm either.')
            

number = int(input('Enter an integer'))
if number == 0:
    print('You entered the number 0.')
elif number > 0:
    print('You entered a positive number.')
else:
    print('You entered a negative number.')
            

age = int(input('How old are you?'))
if age >= 18:
    print('You are an adult!')
else:
    print('You are not an adult.')
            

float('0.01')  #converts the string '0.01' to 0.01
float(10)  #converts the integer 10 to 10.0
            

number = 10
if number == 10:
    print('The number is equal to 10.') #this will be printed
            

number = int(input('Enter an integer'))
if number == 0:
    print('You entered the number 0.')
elif number > 0:
    print('You entered a positive number.')
else:
    print('You entered a negative number.')
            

answer = input('What is your name?')  #The user's answer is saved in the variable answer
            

int(42)  #converts the string '42' to 42
int(3.94)  #converts the decimal number 3.94 to 3
            

print('Hello World')  #prints "Hello World"
print(1+1) #prints the number 2
print(x)  #prints the content of variable x
            

print('Hello World', end='')  #prints "Hello World" without a new line
            

print('Hej','på','dig')  #Prints "Hello to you"
print('Hej','på','dig',sep=' | ',end='!')  #prints "Hello | to | you!" without a new line at the end.
            

from random import randint
roll = randint(1,6)  #a random number 1-6
            

round(7.89)  #rounds to 8
round(1.23)  #rounds to 1
            

round(1.23456,2)  #rounds 1.23
round(1.23456,4)  #rounds to 1.2346
            

str(2.71)  #converts the decimal number 2.71 to the string '2.71'
str(10)  #converts the integer 10 to '10'
            

age = 15
print('You are ' + str(age) + ' years old.')
            

n = int(input('How many numbers do you want to print?'))
i = 1
while i <= n:
    print(i)
    i = i + 1
            

Variables and Data Types

In this section you will learn

• What a variable is and how to create one
• About different data types and conversions between them

Variables - storing data

A variable is for storing data and is used everywhere in programming. Often strings or numbers are stored, but it can also be other more complicated data structures and objects.

A variable is for remembering something while the program is running, for example, the result of a calculation so that it can then be reused elsewhere in the program. It is also common to use variables to store user input or data that has been read from a file.

Variables are used everywhere in programming. The name variable comes from the fact that the program can change (vary) the content of a variable during the program's execution. What is placed in a variable is stored in the computer's working memory and disappears when the program is no longer running.

To create a variable, = (equals sign) is used; to the left of the equals sign is the variable name and to the right of the equals sign is the value to be stored in the variable. It is important here to understand the difference between = in mathematics (is equal to) and in Python (assign value to variable). It is fine to use print(my_variable) to print the content of the variable.

my_variable = 'Hello World'

It is important to write good variable names. The name should describe the information stored in the variable. With good variable names, the program is easier to understand and it becomes easier to do it right. It takes a long time to learn to write good variable names, so don't despair if you find it difficult! In Python, the convention is to write variables with lowercase letters and with _ to separate words.

-- Output from your program will be here --

Data Types

Computers must distinguish between different types of variables, such as strings (text) and numbers. This is because they are stored in different ways in the computer's memory. For example, the number 1 and the string '1' are represented in different ways in memory.

We have already used three common variable types: strings (eng: string), integers (eng: integer) and floating-point numbers (eng: float). Floating-point numbers (pronounced float-numbers) are the most common way for a computer to represent numbers with decimal points.

When you create a variable, Python figures out what type the variable is. In many programming languages, you have to tell what type a variable is when you create it, and then you cannot change what type the variable is. In Python, for example, you can first store a string in a variable and then later store a number in the same variable.

The built-in function type can be used to see what type a variable has, see the example below.

my_text = 'Hi there' #string
my_favorite_number = 1337 #integer
pi = 3.14 #float

my_text_type = type(my_text)
my_favorite_number_type = type(my_favorite_number)
pi_typ = type(pi)

Conversion between different types

The helper functions str, int, and float are available to convert the three types above between each other. For example, int is used to convert a variable to the integer type. Note that it does not always work; for example, the string 'hello' cannot be converted to either an integer or a float.

integer_number = int('42') #the string 42 becomes the integer 42
float_number = float(10) #the integer 10 becomes the float 10.0
text = str(3.14) #the float 3.14 becomes the string 3.14
  

To create a new string that uses, for example, an integer variable, we can perform a conversion.

x = 12
x_text = 'The value of x is equal to ' + str(x)
  

In the case above, when we want to create a string with variables inside, there is an alternative called f-strings.

x = 12
x_text = f'The value of x is equal to {x}'
  

By writing an f before the string, we can use {} around a variable as in the example above. Then the conversion to a string happens automatically.

-- Output from your program will be here --

The built-in function print can receive different types in its argument (what is inside the parentheses of a function is called an argument). The print function automatically converts the argument to a string. If you write, for example, print(5), the number 5 is automatically converted to a string.

Rounding

If a float is converted to an integer using int, the decimals are simply removed.

x = int(3.99)  #x = 3
  

With the built-in function round, we can instead round a float to an integer.

x = round(3.99) #x = 4
  

With the help of round, it is also possible to round to any number of decimals. Inside the parenthesis, we first write the number to be rounded, followed by a comma , and then how many decimals we want to round to.

x = round(1.23456, 2)  #x = 1.23
y = round(1.23456, 4)  #y = 1.2346
  

-- Output from your program will be here --