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Lists in Python
List is a collection of heterogeneous data arranged in a sequence. The values can be of any data type like string,
integer, float, objects or even a list. Each value in a list is called an element and its position in a list is referred by an
index number. The number of elements in a list will make the length of a list. All the elements in a list are separated
by comma and enclosed in square brackets [ ].
List is a mutable data type in Python as the content of the list can be added, modified or deleted by the user
anytime throughout the code. A number of operations can be performed on the list by using a few built-in list
functions which we will study in detail in this chapter.
Important Features of Lists
Based on the above definition, the list has the following important features:
• It is mutable data type.
• It is an ordered sequence of values.
• Each element is separated by comma and enclosed in square brackets [ ].
• Each value/element is accessed by an index number.
• The values can be added, modified or deleted by the user throughout the program.
• It stores the values of different data types.
Creation of List
A list is created by enclosing the values within square brackets. Each value/element is separated by a comma and
stored under a common name. These values can be of different data types. The name follows the rules of naming
conventions for identifiers as shown below:
Examples Commands
Creating an empty list list1 = []
Creating a list with single value list2 = [56]
Creating a list of friends friends = ["Saisha", "Advika", "Arshia"]
Creating a list of marks marks=[92, 91, 89, 95, 93]
Creating a list of students with roll no students = [21, "Gunjan", 94.5, 34, "Rohit", 91.3]
and percentage (list of mixed values)
Creating a list within another list section = ["A", 25, "English", ["B",34], ["C",37],
56.7]
Creating a list with repeated values L1 = [10] * 5 # L1 will have [10, 10, 10, 10, 10]
Creating a list from another sequence alpha = list("hello") #string converted to a list
or string using list() function #output will [‘h’, ‘e’, ‘l’, ‘l’, ‘o’]
Values input from the user in a list L1 = list(input("enter numbers :"))
Access Elements of a List
The elements of a list can be accessed by using its index number starts with 0 (zero). There are two different ways
of using the index number:
• Forward Indexing: The index number begins with 0 till length-1 and we refer the elements from left to right.
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