Python Dictionary

Dictionary in Python is an unordered collection of data values, used to store data values like a map, which, unlike other Data Types that hold only a single value as an element, Dictionary holds key:value pair. Key-value is provided in the dictionary to make it more optimized.

Dictionary Creation

Dictionary can create using curly brackets with keys(should have only immutable data type-string, tuple, int) and values(accept all data types)

#Dictionary Creation
language_dict = {
    1 : "Python",
    2 : "Java",
    3 : "JavaScript"
}

print("Dictionary Creation : ")
print(language_dict)

Output

Dictionary Creation : 
{1: 'Python', 2: 'Java', 3: 'JavaScript'}

Key should be unique - duplicate key creation replace the existing Value

#Dictionary Creation
language_dict = {
    1 : "Python",
    2 : "Java",
    3 : "JavaScript",
    1 : "C++"
}

print("Duplicate keys overrides: ")
print(language_dict)

Output

Duplicate keys overrides: 
{1: 'C++', 2: 'Java', 3: 'JavaScript'}

Dictionary Access

To access dictionary - we can use the key and value function or iterating each items in the given dictionary

#Dictionary Access
language_dict = {
    1 : "Python",
    2 : "Java",
    3 : "JavaScript",
}

print("Access using key : ")
print(language_dict[1])

print("Iteration - To access all value")
for key, value in language_dict.items():
    print(key, value)

Output

Access using key : 
Python
Iteration - To access all value
1 Python
2 Java
3 JavaScript

Dictionary update

Dictionary can be update using the update function

#Dictionary Update
language_dict = {
    1 : "Python",
    2 : "Java",
    3 : "JavaScript",
}

print("Update using key : ")
language_dict[1] = "C++"
print(language_dict)

print("Update using update method")
language_dict.update({1 : "Python"})
print(language_dict)

Output

Update using key : 
{1: 'C++', 2: 'Java', 3: 'JavaScript'}
Update using update method
{1: 'Python', 2: 'Java', 3: 'JavaScript'}

Dictionary update

Since dictionary is mutable, we can perform the specific deletion operation

#Dictionary Update
language_dict = {
    1 : "Python",
    2 : "Java",
    3 : "JavaScript",
    4 : "C++"
}

print("Delete using key : ")
language_dict.pop(4)
print(language_dict)

print("Delete using 'del' keyword")
del language_dict[3]
print(language_dict)

Output

Delete using key : 
{1: 'Python', 2: 'Java', 3: 'JavaScript'}
Delete using 'del' keyword
{1: 'Python', 2: 'Java'}

Dictionary Slicing

Since dictionary are unordered collection, we cannot perform the slicing operation in dictionary data

#Dictionary Slicing
language_dict = {
    1 : "Python",
    2 : "Java",
    3 : "JavaScript",
    4 : "C++"
}

print("Dictionary slicing raises exception : ")
print(language_dict[1:4])

Output

Dictionary slicing raises exception : 
Traceback (most recent call last):
File "<string>", line 10, in <module>
TypeError: unhashable type: 'slice'