Python Data Types

Python has several built-in types.

If you create the name variable assigning it the value “Roger”, automatically this variable is now representing a String data type.

name = "Roger"

You can check which type a variable is using the type() function, passing the variable as an argument, and then comparing the result to str:

name = "Roger"
type(name) == str #True

Or using isinstance():

name = "Roger"
isinstance(name, str) #True

Notice that to see the True value in Python, outside of a REPL, you need to wrap this code inside print(), but for clarity reasons I avoid using it

We used the str class here, but the same works for other data types.

First, we have numbers. Integer numbers are represented using the int class. Floating point numbers (fractions) are of type float:

age = 1
type(age) == int #True
fraction = 0.1
type(fraction) == float #True

You saw how to create a type from a value literal, like this:

name = "Flavio"
age = 20

Python automatically detects the type from the value type.

You can also create a variable of a specific type by using the class constructor, passing a value literal or a variable name:

name = str("Flavio")
anotherName = str(name)

You can also convert from one type to another by using the class constructor. Python will try to determine the correct value, for example extracting a number from a string:

age = int("20")
print(age) #20

fraction = 0.1
intFraction = int(fraction)
print(intFraction) #0

This is called casting. Of course this conversion might not always work depending on the value passed. If you write test instead of 20 in the above string, you’ll get a ValueError: invalid literal for int() with base 10: 'test' error.

Those are just the basics of types. We have a lot more types in Python:

  • complex for complex numbers
  • bool for booleans
  • list for lists
  • tuple for tuples
  • range for ranges
  • dict for dictionaries
  • set for sets

and more!

We’ll explore them all soon.