Creating and indexing lists in Python

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List is the simplest type of data structure in Python programming. A list is used to store a collection of elements of same type (numeric, string, etc.). In Python, a pair of brackets [] indicates the data object is a list type. For example, the following two statements create two lists, in which one is numeric and the other is of string type.

#create a numeric list
N_list = [31,2,33,44,55]
#

#print the list
N_list
Out[2]: [31, 2, 33, 44, 55]

#create a string list
cars = ['BMW', 'Mercedes', 'Tesla', 'Volvo']

#print the list
print(cars)
['BMW', 'Mercedes', 'Tesla', 'Volvo']

Once a list has been created, its elements can be accessed for use in operation. Accessing elements of a list is called indexing. Python also use brackets [] for indexing. For example, the first element of the list ‘cars’ can be indexed and printed out with specific form.

#The first element of the list is printed out
print(cars[0])
BMW

#the first element of the list is printed with its title form
print(cars[0].title())
Bmw

Note that indexing in Python starts from 0, not 1. And the elements can also be indexed from the end of the list by using a minus – symbol in front of the indexing number. The following code examples show how to perform these operations.

#print the second item of the list
print(cars[1])
Mercedes

#print the fourth item of the list
print(cars[3])
Volvo

#print the last item of the list
print(cars[-1])
Volvo

#print the second item from the end of the list
print(cars[-2])
Tesla

You can easily go one step further to create a new data object by using the value of an existing list. Say, in the following example, the first item of the list ‘cars’ is accessed and concatenated with another string to generate a new string object. Note that Python use plus symbol ‘ + ‘ to concatenate strings.

#the first item of the list 'cars' is accessed and #concatenated with string 'info' and '.', and the result
#is assigned to create a new string object 'info'.
info = "I love " + cars[0].title() + "."

print(info)
I love Bmw.

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