Write Python program to perform following operations on Lists: Create list, Access list, Update list (Add item, Remove item), Delete list
A list is a collection which is ordered and changeable.
A list is a collection of items or elements; the sequence of data in a list is ordered.
#totalprogrammingcode
The elements or items in a list can be accessed by their positions i.e. indices
In Python lists are written with square brackets. A list is created by placing all the
items (elements) inside a square brackets [ ], separated by commas.
Lists are mutable. The value of any element inside the list can be changed at any
point of time.
 |
| Write Python program to perform following operations on Lists: Create list, Access list, Update list (Add item, Remove item), Delete list |
The index always starts with 0 and ends with n-1, if the list contains n elements.
a) Creating List: Creating a list is as simple as putting different comma-separated
values between square brackets.
Example:
>>>List1=[‘Java’,’Python’,’Perl’]
>>>List2=[10,20,30,40,50]
b) Accessing List: To access values in lists, use the square brackets for slicing along
with the index or indices to obtain value available at that index.
Example:
>>>List2
[10,20,30,40,50]
>>>List2[1]
20
>>>List2[1:3]
[20,30]
>>>List2[5]
Traceback (most recent call last):
File "<pyshell#71>", line 1, in <module>
List2[5]
IndexError: list index out of range
c) Updating List: 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.
>>>List2
[10,20,30,40,50]
>>>List2[0]=60 #Updating first item
[60,20,30,40,50]
>>>List2[3:4]=70,80
>>>[60,20,30,70,80,50]
i) We can add one item to a list using append() method or add several items using
extend() method.
>>> list1=[10,20,30]
>>> list1
[10, 20, 30]
>>> list1.append(40)
>>> list1
[10, 20, 30, 40]
>>> list1.extend([60,70])
>>> list1
[10, 20, 30, 40, 60, 70]
ii) We can also use + operator to combine two lists. This is also called
concatenation
>>> list1=[10,20,30]
>>> list1
[10, 20, 30]
#totalprogrammingcode
>>> list1+[40,50,60]
[10, 20, 30, 40, 50, 60]
iii) The * operator repeats a list for the given number of times.
>>> list2 ['A', 'B']
>>> list2 *2
['A', 'B', 'A', 'B']
iv) We can insert one item at a desired location by using the method insert()
>>> list1
[10, 20]
>>> list1.insert(1,30)
>>> list1
[10, 30, 20]
d) Deleting List: To remove a list element, you can use either the del statement if you
know exactly which element(s) you are deleting or the remove() method if you do not
know.
i) Del Operator: We can delete one or more items from a list using the keyword del. It
can even delete the list entirely. But it does not store the value for further use.
Example:
>>> list=[10,20,30,40,50]
>>> del list[2]
>>> list
[10, 20, 40, 50]
ii) Remove Operator: We use the remove operator if we know the item that we want
to remove or delete from the list (but not the index)
Example:
>>> list=[10,20,30,40,50]
>>> list.remove(30)
>>> list
[10, 20, 40, 50]
Examples
1. Write a Python program to sum all the items in a list
no = [10,12,13,14,15]
ans = 0
for i in range(0,len(no)):
ans = ans+ no[i]
print("The sum of digit in list :",ans)
2. Write a Python program to find common items from two lists
list1 = [10,20,30,40,50]
list2 = [10,30,70,30,90]
for i in range(len(list1)):
num = list1[i]
for z in range(len(list2)):
num2 = list2[z]
if(num == num2):
print("The common item in list :",num)
3. Write a Python program to reverse a list.
list = [10,20,30,40,50]
list.reverse()
print("Reverse list :",list)
4. Write a Python program to get the largest number from a list.
list = [10,20,30,40,50]
list1 = max(list)
print("Largest item in list :",list1)
