Built-in scope in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the built-in scope in Python?

The built-in scope is the area where Python's built-in functions and names like <code>print()</code>, <code>len()</code>, and <code>int()</code> live. These are always available anywhere in your code without needing to import or define them.

beginner

Where does Python look first when you use a name in your code?

Python first looks in the local scope (inside the current function or block), then in the enclosing scopes (like outer functions), then in the global scope (the main script), and finally in the built-in scope if it doesn't find the name anywhere else.

intermediate

Can you override a built-in function name in your code? What happens?

Yes, you can create a variable or function with the same name as a built-in. This will hide the built-in inside your current scope, so when you use that name, Python uses your version instead of the built-in. This can cause confusion, so it's best to avoid it.

beginner

Example: What will this code print?

print(len([1, 2, 3]))

It will print 3 because len() is a built-in function that returns the number of items in a list.

intermediate

How can you see all the names in the built-in scope?

You can import the <code>builtins</code> module and use <code>dir(builtins)</code> to list all built-in names available in Python.

Which scope does Python check LAST when looking for a variable name?

A Local scope

B Global scope

C Built-in scope

D Enclosing scope

Python checks the built-in scope last after local, enclosing, and global scopes.

What happens if you define a variable named print in your code?

A Your variable hides the built-in print function in that scope.

B The built-in print function is still used.

C Python throws an error.

D The built-in print function is deleted.

Your variable named print hides the built-in function in the current scope.

How can you list all built-in functions and names in Python?

A Use <code>dir(builtins)</code> after importing <code>builtins</code>.

B Use <code>dir()</code> with no arguments.

C Use <code>help()</code>.

D Use <code>list_builtins()</code>.

Import builtins and use dir(builtins) to see all built-in names.

Which of these is NOT a built-in function in Python?

A len()

B print()

C input()

D my_function()

my_function() is not a built-in function; it's a user-defined name.

If a name is not found in local, enclosing, or global scopes, what does Python do?

A Raises a syntax error.

B Looks in the built-in scope.

C Creates a new variable.

D Ignores the name.

Python looks in the built-in scope before raising a NameError.

Explain the order Python uses to find a variable name when you use it in your code.

Think about the LEGB rule.

Describe what happens if you create a variable with the same name as a built-in function.

Consider how Python decides which name to use.