Lists - Python Programming Basics

Lists in python are one of the ways to store data.

  • Lists in python store values in a sequence. The values can be of any data type.
  • You can make a list of lists.
  • Lists in python have many in-built functions that make things like sorting, reversal and finding max and min values trivial. 
  • Lists are mutable i.e. any one of the items of the last can be changed to have another value. 
  • Elements can be added or removed from a list.

Declaring an empty list

To make an empty list, write:

lst = []

The square bracket notation is used to denote a list.

lst = ["val1","val2","val3","val1","val3"]

Appending a value

To add a new value to the list, write:

lst.append("val1")

Removing a value

To remove an element from the list, write:

lst.remove("val4")

Remember: This will only remove the first occurrence of the passed value.

Sorting a list

To sort a list, simply call its sort method.

lst  = [1,0.1,2,4,3]

lst.sort()

Reversing a list

To reverse the elements in a list, use the reverse method of the list.

ls = [1,3,5,7,9]

ls.reverse()

Note: You can use the sort method and then the reverse method to get the list in decreasing order. Alternatively, you can use lst.sort(reverse=True) to do the same.