Accessing elements

We can access data by using keys.

Example

Python

d={1:'ajay', 2:'amit', 3:'manish'}
print(d[1])
print(d[3])

Output

PowerShell

ajay
manish

If the specified key is not available then we will get KeyError.

Example

Python

d={1:'ajay', 2:'amit', 3:'manish'}
print(d[4])

Output

PowerShell

KeyError: 4

We can prevent this by checking whether key is already available or not by using in operator.

Example

Python

d={1:'ajay', 2:'amit', 3:'manish'}
if 4 in d:
  print(d[4])
else:
  print(d[3])

Output

PowerShell

manish

Question

Write a program to enter name and percentage marks in a dictionary and display information on the screen.

Example

Python

rec={}
n=int(input("Enter number of students: "))
i=1
while i <=n:
  name=input("Enter Student Name: ")
  marks=input("Enter % of Marks of Student: ")
  rec[name]=marks
  i=i+1
print("Name of Student","\t","% of marks")
for x in rec:
  print("\t",x,"\t\t",rec[x])

Output

PowerShell

Enter number of students: 3
Enter Student Name: suman
Enter % of Marks of Student: 60%
Enter Student Name: ajay
Enter % of Marks of Student: 70%
Enter Student Name: amit
Enter % of Marks of Student: 80%
Name of Student       % of marks
suman          60%
ajay           70 %
amit           80%

Update Elements

Syntax

Python

d[key]=value

If the key is not available then a new entry will be added to the dictionary with the specified key-value pair. If the key is already available then old value will be replaced with new value.

Example

Python

d={1:"ajay", 2:"amit", 3:"manish"}
print(d)
d[4]="suman"
print(d)
d[1]="seema"
print(d)

Output

PowerShell

{1: 'ajay', 2: 'amit', 3: 'manish'}
{1: 'ajay', 2: 'amit', 3: 'manish', 4: 'suman'}
{1: 'seema', 2: 'amit', 3: 'manish', 4: 'suman'

Delete Elements

There are three methods to delete elements.

del d[key]

It deletes entry associated with the specified key.
If the key is not available then we will get KeyError.

Example

Python

d={1:"ajay", 2:"amit", 3:"manish"}
print(d)
del d[1]
print(d)
del d[4]

Output

PowerShell

{1:"ajay",2:"amit",3:"manish"}
{2:"amit",3:"manish"}
KeyError: 4

d.clear()

To remove all entries from the dictionary

Example

Python

d={1:"ajay", 2:"amit", 3:"manish"}
print(d)
d.clear()
print(d)

Output

PowerShell

{1:"ajay",2:"amit",3:"manish"}
{}

del d

To delete total dictionary. We cannot access d after delete.

Example

Python

d={1:"ajay", 2:"amit", 3:"manish"}
print(d)
del d
print(d)

Output

PowerShell

{1:"ajay",2:"amit",3:"manish"}
NameError: name 'd' is not defined

Ungraded Questions

Get ready for an exhilarating evaluation of your understanding! Brace yourself as we dive into the upcoming assessment. Your active participation is key, so make sure to attend and demonstrate your knowledge. Let’s embark on this exciting learning journey together!

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