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Modifying Existing Values in a List
List is mutable so data can be easily modified by overwriting a new value to an existing value in a given list by
using an assignment operator (=). Syntax to modify existing values in a list is:
list[index] = newvalue
For example,
Commands Output
L1=[10,20,40,50] [10, 20, 40, 100]
L1[3]=100
print(L1)
L1=[10,20,40,50] [10, 'abc', 'xyz', 100]
L1[1:3]=["abc","xyz"]
print(L1)
Removing Elements from a List
There are two different functions used to remove elements in an existing list remove() and pop(). Let us learn
about these functions in detail.
The remove( ) Function
The remove() function removes the first occurrence of the element with the specified value. It means only one
value can be removed at a time even if there are duplicate values in the list. If you wish to remove multiple values
then this function can be used within a loop where it repeats itself a specific number of times. The syntax of the
remove() function is:
list.remove(<single value>)
For example,
Commands Output
marks = [23, 34, 23, 45, 56, 78, 56] [34, 23, 45, 56, 78, 56]
marks.remove(23)
print(marks)
marks = [23, 34, 23, 45, 56, 78, 56] [23, 34, 23, 45, 78, 56]
marks.remove(56)
print(marks)
marks = [23, 34, 23, 45, 56, 78, 56] ValueError: list.remove(x): x not in list
marks.remove(72)
print(marks)
The pop( ) Function
The pop() function removes an element from the list based on the index number specified in the function and
returns the deleted value. In case no index number is given then by default it removes the last element from the
list. If we try to remove an index number which does not exist then it gives an IndexError.
Introduction to Python 255

