In this tutorial we will study the List Concept in Python.
List in python is a sequence or collection of elements. Unlike arrays in C programming language, lists in python differ in three ways.
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Difference between the list in python and array in C Programming language.
1. List in python can have heterogeneous elements.
2. Array supports both direct and sequential access. List supports on direct access.
3. List can have list as a element.
An empty list can be defined using list() function or empty square brackets.
list1 = list() OR list1 = []
Both will create an empty list.
The following example creates a list with three elements of the same type, and prints the elements of a list using the print function.
list1 = list(10, 20, 30) print (list1)
Output of the program is: [10, 20, 30]
In the following example, we will understand how to create a list with three elements of heterogeneous type. Here two elements are of type integer, two strings and one element is of double type.
list1 = list(10, 'Raj', 30, 'Sachin', 10.20) print(list1)
Like C, Python stores the elements of the list at numeric indices. You can use indexing operator to access the elements of a list in python. Next example shows how to access the list elements using the index operator.
l1 = [10, 20, 30] print (l1[0]) print (l1[2])
OUTPUT is:
10
20
Now, we will see how to create and display the list with nested elements.
l1 = ['spam', 5, [10, ['a', 20]], 'India'] print (l1[0]) print (l1[1]) print (l1[2]) print (l1[3]) print (l1[2][0]) print (l1[2][1][0]) print (l1[2][1][1])
In the above program we have created list “l1” with 4 elements. Then we have shown how to access and display the individual elements using index operator.
spam 5 [10, ['a', 20]] India 10 a 20
Next example shows how to modify the list elements.
l1 = [10, 20, 30]
print ("Before Modificaton:", l1)
l1[0] = 50
l1[1] = 60
l1[2] = 80
#l1[0:3] = [50, 60, 80]
print ("After Modificaton:", l1)This program creates a list with three elements and displays the original elements of the list. Then, modifies the list elements. Finally, the program displays the modified elements a list.
Before Modificaton: [10, 20, 30] After Modificaton: [50, 60, 80]
The presence of an element in a list is verified using in operator. If element is present then “in” operator return true otherwise false.
l1 = [10, 20, 30] 10 in l1 l1 = [10, 20, 30] 40 in l1
First one returns true as 10 is present in l1 and second returns false 40 is not present in l1.
Summary of List Concept in Python:
In this tutorial we have discussed, the definition of a list, how list differs from an array in C. Also we have seen how to create, display entire list and individual elements of a list using index operator. Finally, we, have seen list modification and “in” operator.
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