More Data Structures

Value semantics and reference semantics

refer to how parameters are passed to a function

Value semantics

Behavior where variables store a value. When a
variable is passed as a parameter, the value of the actual parameter is
copied into the formal parameter.

Reference semantics

Behavior where variables store memory addresses
or locations of objects. When a reference is assigned or passed as a
parameter, the formal parameter refers to the same object as the actual
parameter.

variables of type… store values directly

ints, floats, booleans, strings, tuples

variables of object types store references to memory

lists, dictionaries, sets, panels

mutability

the ability to be changed or mutated

Immutable variables

ints, floats, strings, bools, tuples

Operations that try to change the value of an immutable object…

create a new object

Operations that change the value of a mutable object…

can change the object

Immutable

quicker to access, fundamentally expensive to “change” because doing so involves creating a new copy.

Mutable

relatively cheap to change because you are not creating a new copy

Lists and DrawingPanel

are mutable

Why are lists and objects mutable?

Efficiency and sharing

Efficiency

copying large objects slows down a program

Sharing

it’s useful to share an object’s data among functions

When a mutable object is passed as a parameter…

the function can change it

If the parameter is modified…

it will affect the original object

Lists are mutable

true

swap_all

accepts two lists of integers as parameters and swaps their entire contents. Assumes two lists are the same length.

Tuples are similar to a list but __ be altered

cannot (i.e., immutable)

Tuples

goods for storing related data.