Dictionaries

Dictionaries¶

• Dictionaries are used to store data values in key:value pairs.

Creating and Accessing Dictionary¶

In [1]:

person = {
    'name': 'Alice', 
    'age': 25
    }
print(person['name'])  # Accessing value by key

person = { 'name': 'Alice', 'age': 25 } print(person['name']) # Accessing value by key

Alice

Adding, Updating, and Removing Elements¶

In [13]:

## add city
person['city'] = 'Kathmandu'

## update age
person['age'] = 50
print(person)

## add city person['city'] = 'Kathmandu' ## update age person['age'] = 50 print(person)

{'name': 'Alice', 'age': 50, 'city': 'Kathmandu'}

In [14]:

## delete name
del person['name']
print(person)

## delete name del person['name'] print(person)

{'age': 50, 'city': 'Kathmandu'}

Dictionary Methods¶

Method	Description	Example Code	Output
keys()	Returns a list of dictionary keys	d = {'a': 1} d.keys()	dict_keys(['a'])
values()	Returns a list of dictionary values	d = {'a': 1} d.values()	dict_values([1])
items()	Returns a list of key-value tuple pairs	d = {'a': 1} d.items()	dict_items([('a', 1)])
get()	Returns value for key if key exists	d = {'a': 1} d.get('a')	1
update()	Updates dictionary with another dictionary	d.update({'b': 2})	{'a': 1, 'b': 2}
pop()	Removes and returns value for key	d.pop('a')	1 and {'b': 2}
clear()	Removes all items	d.clear()	{}

Exercise Create a dictionary with movie data (title, year, rating)¶

Tasks:

• Access the title.
• Update the rating.
• Add a new key: 'actor'.
• Delete the year.
• Print all keys and values.

In [2]:

print(person)

print(person)

{'name': 'Alice', 'age': 25}

In [3]:

person.keys()

person.keys()

Out[3]:

dict_keys(['name', 'age'])

In [4]:

person.values()

person.values()

Out[4]:

dict_values(['Alice', 25])

In [5]:

person.items()

person.items()

Out[5]:

dict_items([('name', 'Alice'), ('age', 25)])

In [6]:

person

person

Out[6]:

{'name': 'Alice', 'age': 25}

In [7]:

person['location']

person['location']

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
Cell In[7], line 1
----> 1 person['location']

KeyError: 'location'

In [9]:

person.get('name')

person.get('name')

Out[9]:

'Alice'

In [11]:

person.get('location', 'Kathmandu')

person.get('location', 'Kathmandu')

Out[11]:

'Kathmandu'

In [12]:

person.get('dsafaskhj', 'Kathmandu')

person.get('dsafaskhj', 'Kathmandu')

Out[12]:

'Kathmandu'

type casting¶

In [14]:

my_tuple = (1, 2, 3, 4)
my_list = list(my_tuple)
my_list.append(5)
my_tuple = tuple(my_list)
print(my_tuple)

my_tuple = (1, 2, 3, 4) my_list = list(my_tuple) my_list.append(5) my_tuple = tuple(my_list) print(my_tuple)

(1, 2, 3, 4, 5)

In [ ]: