What Built-ins Are

Built-in Functions

What Built-ins Are

In this tutorial, we'll understand functions Python gives you automatically.

Built-in functions are functions Python gives you automatically.

You do not need to install or import anything to use them:

print("Hello")
len("Python")
type(42)

They are always available in normal Python code.

Why Built-ins Matter

Built-ins solve common tasks:

  • Show output with print()
  • Get input with input()
  • Count items with len()
  • Convert values with int(), float(), and str()
  • Sort values with sorted()
  • Add numbers with sum()

Instead of writing these tools yourself, you use the versions Python already provides.

Functions vs Methods

A function is called by name:

len("hello")

A method is attached to a value:

"hello".upper()

Both do useful work, but they are called differently.

Built-ins Are Not Magic

You still need to understand what each function expects.

int("42")      # works
int("hello")   # error

int() can convert text that looks like a whole number. It cannot convert any text.

Finding Help

Python has many built-ins, but you do not need to memorise them all. Learn the common ones first, then look up others when you need them.

You can also experiment in the Python shell:

>>> len("hello")
5
>>> max([3, 9, 1])
9

Practice

Use print(), len(), and type() on three different values.