Dictionary

dict Data Type

A dict (dictionary) variable is a collection of key:value pairs.

These pairs are separated by commas and the sequence is delimited by braces { }.

To establish the correspondence between the elements constituting the key and value pair, we use the symbol : (colon.)

To access the values ​​of a dict variable, we use the brackets [ ].

The value assigned to a key must be non-mutable (number, tuple, string, etc.)

The value assigned to a key must be unique.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
print(data)
print(data['org'])
print(data.keys())
print(data.values())

Add Items

We add an element to a dict by assigning a value component to a new key component.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
print(data)
# Add an item
data['edu'] = 'Education'
print(data)

Remove Items

The del statement is used to delete an element from a dict.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
print(data)
# Remove an item
del data['net']
print(data)

The pop() method is used to remove and return an element of specified index from a dict.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
print(data)
# Remove an item
element = data.pop('com')
print(data)
print('Popped element:', element)

The clear() method is used to remove all elements from a dict.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
print(data)
# Clear the dictionary
data.clear()
print(data)

Change Items

The dict data type is mutable in nature.

We change the value component of an element of a dict by referring to its key component.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Networking'
}
print(data)
# Change the value of an item
data['net'] = 'Network'
print(data)

Iteration through a dict

A dict is bounded and iterable: we can iterate through the key components of its elements in a for loop.

We use the membership operator in to iterate through the elements of a dict.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
# iterate on dictionary keys one by one
for domain in data :
   entity = data[domain]
   print(domain, ':', entity)

Length of a dict

The length of a dict is the number of elements it contains.

The len() function returns the length of a dict.

Example

data = {
'com' : 'Commercial',
'org' : 'Organization',
'net' : 'Network'
}
# get dictionary length
print(len(data))

dict Methods

The following are built-in methods for a dict object.