Lists

Programming basics

A list is a data structure in Python that is a mutable, or changeable, ordered sequence of elements. Each element or value that is inside of a list is called an item. Just as strings are defined as characters between quotes, lists are defined by having values between square brackets [ ].

Please be careful as lists can be thought of as analogous to arrays, but they aren't the same thing. Arrays traditionally have a fixed memory size whilst lists have dynamic memory allocation. When you are working in Python, call a list a list. When you are working in PHP or Javascript, call an array an array. When you are working in C, call for help!

Lists, like arrays are indexed starting at zero. The first element in a list is the "zero-th" element.

Creating a list

# The code below creates a list named polishAnimals 
polishAnimals = ['Bison', 'Moose', 'Deer', 'Lynx', 'Wolf', 'Beaver', 'Otter']

Accessing a list

# If you want to print a list (kind of ugly) you can simply:

print(polishAnimals)

# However, it is far more common to slice into a list
# The code below accesses the 2nd item in the list named 'polishAnimals'

print(polishAnimals[2])

# there is a lot more to slicing in Python.

Inserting into a list

# if we want to add onto a list (append) we could simply use the append method. The code below appends wild board onto the end of our list.

polishAnimals.append('wild boar')

# if we wanted to replace a certain element, we could simply overwrite it. Below we are replacing the 2nd item of our list with a new animal:

polishAnimals[1] = 'Stork'

Standards

• Construct algorithms using pre- defined sub-programmes, one- dimensional arrays and/or collections.

Give a sequence of brief answers with no explanation.

Develop information in a diagrammatic or logical form.