A data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data, it is an algebraic structure about data.
~ Wikipedia

List

Ordered, mutable, and allows duplicate elements.

my_list = [1, 2, 3, 4, 5]

# Lists are 0-indexed
my_list[0]        # => 1
my_list[3]        # => 4
my_list[-1]       # => 5
my_list[1:3]      # => [2, 3]

len(my_list)      # => 5

List Methods

my_list.append(6) # => None ; my_list is now [1, 2, 3, 4, 5, 6]
my_list.remove(2) # => None ; my_list is now [1, 3, 4, 5, 6]
my_list.pop()     # => 6    ; my_list is now [1, 3, 4, 5]

List

In python, there are two ways to iterate over a list with a for loop.

• The first way is to the index of the elements.

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

• The second way is to iterate over the elements themselves.

  for element in my_list:
      print(element)
  

List Comprehensions

Concise way to create lists.

squares = [x**2 for x in range(10)]
even_squares = [x**2 for x in range(10) if x % 2 == 0]

Lists of Lists (2D-Array)

Lists can contain other lists. This is how you can create a matrix!

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
matrix[0]     # => [1, 2, 3]
matrix[1][2]  # => 6

for row in matrix:
    for element in row:
        print(element)
      
for i in range(len(matrix)):
    for j in range(len(matrix[i])):
        print(matrix[i][j])