Loops and lists: an overview

Using loops is very important for writing efficient code. Loops are used to perform the same calculation multiple times, for example iterating over all items in a list, or until some condition is met. The most common loop type we’ll come accross is the for loop

For loop characteristics

The example code below shows the structure of a for loop. This code is not interactive, it’s just to show you the basic syntax.

for x in range(10):
  #instructions for operating on x go inside the loop
  print(x)
print('Done')

Using the above example, we can see a for loop has the following characteristics:

• A variable we use to access each item in a sequence

• A sequence to iterate over (defined here using the inbuilt range function).

• Some operations performed on each item in the sequence

A for loop might be written inside a function, and we will see examples of this today.