Learn to Code: Python for Absolute Beginners/

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Lists with Loops

Lists with Loops

Learn to use lists with the help of loops in Python.

We'll cover the following...

The for loop with lists

The individual values in a list are accessed through an index number. The for loop variable can be used as an index number. However, the list values can also be used directly in a for loop.

The following program demonstrates the various ways of accessing list elements:

Python 3.10.4
vals = [-5, 'Python', 3.8]
 
print("Using loop variable as a list index")
for i in [0,1,2]:
   print(vals[i])
 
print("\nDirectly accessing the elements")
for v in vals:
   print (v)
 
mix = ['a',1,2.5,'i',50,6,'m',4.4,6.7,'s','@educative']
print('\nList index using "len()" in range()')
for v in range(len(mix)):
   print (mix[v])

In the code above:

  • The new item is the len ( ) function, which is used to get the length of the list.
  • The first for loop accesses the list values with the help of the loop variable i.
  • The second for loop directly accesses the list values.
  • The third for loop accesses the list values with the help of loop variable v and the functions range and len.

The while loop with lists

We usually use the while loop to deal with lists when the number of iterations is not fixed. For a simple example, let’s say we want to generate n terms of a Fibonacci sequence and store it in a list, where n is the user input. A Fibonacci sequence is a sequence in which each number is the sum of the two preceding ones except the first two terms.

Let’s start by noting a few terms of this sequence: 0,1,1,2,3,5,8,13,21,34,…0, 1, 1, 2, 3, 5, 8, 13, 21, 34, … ...