Names and Functions

Values

Primitive Data Types

Integers, Strings, Floats, Booleans Expressions evaluate to values

Names

Assigning values to names, otherwise known as variables (can also represent functions)

Assignment Statements

The statement which defines the variable

Tip

Python does not evaluate assignment statements (nothing is returned when you assign a variable)

Variables assigned in Python are inherently mutable (that does not mean the object is mutable)

Split Expressions

a = 1
b = 2
a, b = b, a # Operation happens instantly: The values for a and b are swapped 

Environment Diagram

Allows for the tracking of value of variables on a per-frame basis, however will typically show the final state of the program Environment diagrams allow you to track the value of variables and abstract away sequences of computation

Functions

A sequence of code that performs a specific task and can be reused easily.

Inputs and Outputs

• Inputs are known as arguments
• Outputs are known as return values

Function Creation

• Functions can be created with the def statement
• Indents are required to give scope, give body, etc.

Anatomy

Function signature

Indicates name and number of arguments

Function Body

Defines the computation performed when the function is applied

Default Return

Default return type is None (equivalent to null).

Environment Diagram Scopes

Environment Diagram has different frames (or scopes).

Calling user-defined functions

1. Retrieve intrinsic name (i.e. the real name, or the real function, as function names can be reassigned)
2. Bind function parameters to arguments within the frame
3. Execute the body with the environment