Python 3 - Lists

The most basic data structure in Python is the sequence. Each element of a sequence is assigned a number - its position or index. The first index is zero, the second index is one, and so forth.
Python has six built-in types of sequences, but the most common ones are lists and tuples, which we would see in this tutorial.
There are certain things you can do with all the sequence types. These operations include indexing, slicing, adding, multiplying, and checking for membership. In addition, Python has built-in functions for finding the length of a sequence and for finding its largest and smallest elements.
The list is the most versatile datatype available in Python, which can be written as a list of comma-separated values (items) between square brackets. Important thing about a list is that the items in a list need not be of the same type.
Creating a list is as simple as putting different comma-separated values between square brackets. For example −
list1 = ['physics', 'chemistry', 1997, 2000];
list2 = [1, 2, 3, 4, 5 ];
list3 = ["a", "b", "c", "d"];
Similar to string indices, list indices start at 0, and lists can be sliced, concatenated and so on.
To access values in lists, use the square brackets for slicing along with the index or indices to obtain value available at that index. For example −
#!/usr/bin/python3

list1 = ['physics', 'chemistry', 1997, 2000]
list2 = [1, 2, 3, 4, 5, 6, 7 ]

print ("list1[0]: ", list1[0])
print ("list2[1:5]: ", list2[1:5])
When the above code is executed, it produces the following result −
list1[0]:  physics
list2[1:5]:  [2, 3, 4, 5]

You can update single or multiple elements of lists by giving the slice on the left-hand side of the assignment operator, and you can add to elements in a list with the append() method. For example −
#!/usr/bin/python3

list = ['physics', 'chemistry', 1997, 2000]
print ("Value available at index 2 : ", list[2])

list[2] = 2001
print ("New value available at index 2 : ", list[2])
Note − The append() method is discussed in the subsequent section.
When the above code is executed, it produces the following result −
Value available at index 2 :  1997
New value available at index 2 :  2001

To remove a list element, you can use either the del statement if you know exactly which element(s) you are deleting. You can use the remove() method if you do not know exactly which items to delete. For example −
#!/usr/bin/python3

list = ['physics', 'chemistry', 1997, 2000]
print (list)

del list[2]
print ("After deleting value at index 2 : ", list)
When the above code is executed, it produces the following result −
['physics', 'chemistry', 1997, 2000]
After deleting value at index 2 :  ['physics', 'chemistry', 2000]

Note − remove() method is discussed in subsequent section.
Lists respond to the + and * operators much like strings; they mean concatenation and repetition here too, except that the result is a new list, not a string.
In fact, lists respond to all of the general sequence operations we used on strings in the prior chapter.
Since lists are sequences, indexing and slicing work the same way for lists as they do for strings.
Assuming the following input −
L = ['C++'', 'Java', 'Python']
Python includes the following list functions −
Gives the total length of the list.
Returns item from the list with max value.
Returns item from the list with min value.
Converts a tuple into list.
Python includes the following list methods −
Appends object obj to list
Returns count of how many times obj occurs in list
Appends the contents of seq to list
Returns the lowest index in list that obj appears
Inserts object obj into list at offset index
Removes and returns last object or obj from list
Removes object obj from list
Reverses objects of list in place
Sorts objects of list, use compare func if given

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