Using Lists (Arrays) in Python

Lists in Python are used to store multiple items in a single variable. Lists can be one-dimensional (1D) or two-dimensional (2D), and they provide a way to organize and manipulate data efficiently.

One-Dimensional (1D) Arrays

Declaration and Initialization

Empty List:

colours = []

Fixed Length with Default Values:

colours = [None] * 5 # Creates a list with 5 `None` elements

With Values Assigned:

colours = ["Blue", "Pink", "Green", "Yellow", "Red"]

Access and Assignment

• Accessing Elements: print(colours[2]) # Output: Green
• Assigning Values: colours[3] = "Orange" # Changes Yellow to Orange

Example

colours = ["Blue", "Pink", "Green", "Yellow", "Red"]
print(colours[2])  # Output: Green
colours[3] = "Orange"

When outputting all elements within an array a for loop is used

for i in range(len(colours)):
  print(colours[i])

This will output each element on a seperate line

Blue
Pink
Green
Orange
Red

Two-Dimensional (2D) Arrays

A 2d array is one were each element is an array in itself.

below the first element is gameboard[0]

gameboard = [
    ["Pawn", None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    # ... other rows ...
]

That is the row

["Pawn", None, None, None, None, None, None, None]

Pawn is in position 0 in this array

Therefore gameboard[0][0] is how we access Pawn

I could assign a new element into this array

gameboard[1][0] = "Knight"

gameboard is now equal to

gameboard = [
    ["Pawn", None, None, None, None, None, None, None],
    ["Knight", None, None, None, None, None, None, None],
    # ... other rows ...
]

Declaration and Initialization

With Values Assigned:

gameboard = [
    ["Pawn", None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    # ... other rows ...
]

Accessing Elements in a 2d array with a loop

Lets setup our gameboard so it matches an actual Chess board during the initial setup.

gameboard = [
    ["Castle", "Bishop", "Knight", "King", "Queen", "Knight", "Bishop", "Castle"],
    ["Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn"],
    [None, None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    ["Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn"],
    ["Castle", "Bishop", "Knight", "King", "Queen", "Knight", "Bishop", "Castle"],
]

print("Initial gameboard:")

# accesses the rows
for i in range(8):
  #accesses the columns
  for j in range(8):
    # prints out the gameboard row by row
    print(gameboard[i][j])

Now our nested for loop will give us all of the pieces on the board. But to make it more useable we can use a few tricks

Firstly we can provide the coordinate of each position using the i and j values of the loop

print("Row "+str(i)+": Col "+str(j)+" = "gameboard[i][j])

gameboard = [
    ["Castle", "Bishop", "Knight", "King", "Queen", "Knight", "Bishop", "Castle"],
    ["Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn"],
    [None, None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    [None, None, None, None, None, None, None, None],
    ["Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn", "Pawn"],
    ["Castle", "Bishop", "Knight", "King", "Queen", "Knight", "Bishop", "Castle"],
]

print("Initial gameboard:")

# accesses the rows
for i in range(8):
  #accesses the columns
  for j in range(8):
    # prints out the gameboard row by row
    print("Row "+str(i)+": Col "+str(j)+" = "gameboard[i][j])

Even better would be to use the python built in , end=" " which stops a new line being printed. But then using the end of the row loop to print a new line.

# accesses the rows
for i in range(8):
  #accesses the columns
  for j in range(8):
    # prints out the gameboard row by row
    print(gameboard[i][j], end=" ")
  # new line once row finished
  print()