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Basic Data Types

In python, every value has a data type, which tells Python how it can be used.

Basic Data Types:

  • String - a piece of text ("Hello", "apple", ...)
  • Int - an integer number (-10, -2, 0, 1, 7, 500, ...)
  • Float - a real number (-10.5, 4.0, 3.3333, 20.16, ...)
  • Bool - a boolean value (True, False)

It’s important to understand what you can and cannot do with each data type. For example, adding a number to a boolean value usually doesn’t make sense and can lead to errors.

To check the type of a value, you can use the type() function.

type(5)

Obviously this on its own won't show you anything, you can pair it with the print() function.

print(type(5)) # Output: <class 'int'>

You can also use variables with this function:

number = 5

print(type(number)) # Output: <class 'int'>

Or even store the output of the type() function itself in a variable:

number = type(5)

print(number) # Output: <class 'int'>

Casters

Casting is the proccess of converting a value from one data type to another.

There is a set of Python functions that allows you to do that:

  • int() - turns the value to an integer
  • float() - turns the value to a float
  • str() - turns the value to a string
  • bool() - turns the value to a boolean

Strings

You can do a few things with strings.

You can concatenate them:

print("Hello " + "world!") # Output: Hello world!

But what if you want to concatenate a string with a number?

print("Number " + 5) # This will throw an error

You can either wrap your integer in quotes and it will turn into a string:

print("Number " + "5") # Output: Number 5

Or you can cast your integer into a string:

print("Number " + str(5)) # Output: Number 5

It will also work with variables:

my_text = "Number "
my_number = 5

print(my_text + str(my_number)) # Output: Number 5

What if it is the other way around:

number_1 = "5"
number_2 = "10"

print(number_1 + number_2) # Output: 510

You can just cast them to integers:

number_1 = "5"
number_2 = "10"

print(int(number_1) + int(number_2)) # Output: 15

Or even floats:

number_1 = "5"
number_2 = "10"

print(float(number_1) + float(number_2)) # Output: 15.0

Something useful you can also do is multiply a string with an integer n:

print("a"*10) # Output: aaaaaaaaaa

It will just repeat the string n times.

Int and Float

Ints and floats are different data types, but when python is doing calculations with them, it just converts them to the correct data type.

Take this example:

print(5/2) # Output: 2.5

Despite using two integers, Python knows the output needs to be a float so it allows and converts it automatically.

Another example:

print(5 + 2.0) # Output: 7.0

We are doing the sum of an integer and a float, but Python just converts the integer to float, this is what is called implicit type conversion.

Next topic: ArithmeticOperators