Dictionary in Python

A dictionary is a vital knowledge kind in Python programming. It’s a assortment of information values which are unordered. Python dictionary is used to retailer gadgets wherein every merchandise has a key-value pair. The dictionary is made up of those key-value pairs, and this makes the dictionary extra optimized. 

For instance –

Dict = {1: 'Studying', 2: 'For', 3: 'Life'}
print(Dict)

Right here, 

The colon is used to pair keys with the values.

The comma is used as a separator for the weather. 

The output is:

{1: ‘Learnings’, 2: ‘For’, 3: ‘Life’}

Python dictionary append is solely used so as to add key/worth to the present dictionary. The dictionary objects are mutable. Not like different objects, the dictionary merely shops a key together with its worth. Subsequently, the mixture of a key and its subsequent worth represents a single component within the Python dictionary.  

Restrictions on Key Dictionaries

Beneath are enlisted some restrictions on the important thing dictionaries –

• A given key seems solely as soon as in a dictionary. Duplicates of keys aren’t allowed. 
• It received’t make sense when you map a specific key greater than as soon as. That is so as a result of the dictionary will map every key to its worth.
• In case of a duplication of a key, the final one might be thought-about.
• If a secret’s specified a second time after the creation of a dictionary, then the second time might be thought-about as it is going to override the primary time.
• The important thing should be immutable, which implies that the info kind may be an integer, string, tuple, boolean, and so forth. Subsequently, lists or one other dictionary cannot be used as they’re changeable.  

Methods to append a component to a key in a dictionary with Python?

Making a Dictionary

In Python, you may create a dictionary simply utilizing fastened keys and values. The sequence of components is positioned inside curly brackets, and key: values are separated by commas. It should be famous that the worth of keys may be repeated however cannot have duplicates. Additionally, keys ought to have immutable knowledge varieties comparable to strings, tuples, or numbers. 

Right here’s an instance –

# Making a Dictionary
# with Integer Keys
Dict = {1: 'Studying', 2: 'For', 3: Life}
print("nDictionary with the usage of Integer Keys: ")
print(Dict)
  
# Making a Dictionary
# with Blended keys
Dict = {'Identify': ‘Nice Studying’, 1: [1, 2, 3, 4]}
print("nDictionary with the usage of Blended Keys: ")
print(Dict)

The output is :

Dictionary with the usage of Integer Keys: 

{1: ‘Studying’, 2: ‘For’, 3: ‘Life’}

Dictionary with the usage of Blended Keys: 

{‘Identify’: ‘GreatLearning’, 1: [1, 2, 3, 4]}

Dictionary with integer keys

Right here’s tips on how to create a dictionary utilizing the integer keys –

# creating the dictionary
dict_a = {1 : "India", 2 : "UK", 3 : "US", 4 : "Canada"}

# printing the dictionary
print("Dictionary 'dict_a' is...")
print(dict_a)

# printing the keys solely
print("Dictionary 'dict_a' keys...")
for x in dict_a:
    print(x)

# printing the values solely
print("Dictionary 'dict_a' values...")
for x in dict_a.values():
    print(x)

# printing the keys & values
print("Dictionary 'dict_a' keys & values...")
for x, y in dict_a.gadgets():
    print(x, ':', y)

The output is:

Dictionary ‘dict_a’ is…

{1: ‘India’, 2: ‘USA’, 3: ‘UK’, 4: ‘Canada’}

Dictionary ‘dict_a’ keys…

1

2

3

4

Dictionary ‘dict_a’ values…

India

USA

UK

Canada

Dictionary ‘dict_a’ keys & values…

1 : India

2 : UK

3 : US

4 : Canada

Accessing components of a dictionary

Key names are used to entry components of a dictionary. To entry the weather, it’s essential use sq. brackets ([‘key’]) with the important thing inside it. 

Right here’s an instance –

# Python program to exhibit
# accessing a component from a dictionary
  
# Making a Dictionary
Dict = {1: 'Studying', 'identify': 'For', 3: 'Life'}
  
# accessing a component utilizing key
print("Accessing a component utilizing key:")
print(Dict['name'])
  
# accessing a component utilizing key
print("Accessing a component utilizing key:")
print(Dict[1])

The output is:

Accessing a component utilizing key:

For

Accessing a component utilizing key:

Life

Different technique 

There’s one other technique known as get() that’s used to entry components from a dictionary. On this technique, the secret is accepted as an argument and returned with a price. 

Right here’s an instance –

# Making a Dictionary
Dict = {1: 'Studying', 'identify': 'For', 3: 'Life'}
  
# accessing a component utilizing get()
# technique
print("Accessing a component utilizing get:")
print(Dict.get(3))

The output is:

Accessing a component utilizing get:

Life

Deleting component(s) in a dictionary

You’ll be able to delete components in a dictionary utilizing the ‘del’ key phrase.

The syntax is –

del dict['yourkey']  #It will take away the component along with your key.

Use the next syntax to delete the whole dictionary –

del my_dict  # this can delete the dictionary with identify my_dict

One other various is to make use of the clear() technique. This technique helps to scrub the content material contained in the dictionary and empty it. The syntax is –

Allow us to examine an instance of the deletion of components that end in emptying the whole dictionary –

my_dict = {"username": "ABC", "e-mail": "abc@gmail.com", "location":"Gurgaon"}
del my_dict['username']  # it is going to take away "username": "ABC" from my_dict
print(my_dict)
my_dict.clear()  # until will make the dictionarymy_dictempty
print(my_dict)
delmy_dict # this can delete the dictionarymy_dict
print(my_dict)

The output is:

{’e-mail’: ‘abc@gmail.com’, ‘location’: ‘Gurgaon’}

{}

Traceback (most up-to-date name final):

  File “foremost.py”, line 7, in <module>

    print(my_dict)

NameError: identify ‘my_dict’ is just not outlined

Deleting Ingredient(s) from dictionary utilizing pop() technique

The dict.pop() technique can also be used to delete components from a dictionary. Utilizing the built-in pop() technique, you may simply delete a component based mostly on its given key. The syntax is:

dict.pop(key, defaultvalue)

The pop() technique returns the worth of the eliminated key. In case of the absence of the given key, it is going to return the default worth. If neither the default worth nor the secret is current, it is going to give an error. 

Right here’s an instance that exhibits the deletion of components utilizing dict.pop() –

my_dict = {"username": "ABC", "e-mail": "abc@gmail.com", "location":"Gurgaon"}
my_dict.pop("username")
print(my_dict)

The output is:

{’e-mail’: ‘abc@gmail.com’, ‘location’: ‘Gurgaon’}

Appending component(s) to a dictionary

It’s simple to append components to the present dictionary utilizing the dictionary identify adopted by sq. brackets with a key inside it and assigning a price to it. 

Right here’s an instance:

my_dict = {"username": "ABC", "e-mail": "abc@gmail.com", "location":"Gurgaon"}

my_dict['name']='Nick'

print(my_dict)

The output is:

{‘username’: ‘ABC’, ’e-mail’: ‘abc@gmail.com’, ‘location’: ‘Gurgaon’, ‘identify’: ‘Nick’}

Updating current component(s) in a dictionary

For updating the present components in a dictionary, you want a reference to the important thing whose worth must be up to date. 

On this instance, we are going to replace the username from ABC to XYZ. Right here’s tips on how to do it:

my_dict = {"username": "ABC", "e-mail": "abc@gmail.com", "location":"Gurgaon"}

my_dict["username"] = "XYZ"

print(my_dict)

The output is:

{‘username’: ‘XYZ’, ’e-mail’: ‘abc@gmail.com’, ‘location’: ‘Gurgaon’}

Insert a dictionary into one other dictionary

Allow us to contemplate an instance with two dictionaries – Dictionary 1 and Dictionary 2 as proven under –

Dictionary 1:

my_dict = {“username”: “ABC”, “e-mail”: “abc@gmail.com”, “location”:”Gurgaon”}

Dictionary 2:

my_dict1 = {“firstName” : “Nick”, “lastName”: “Jonas”}

Now we wish to merge Dictionary 1 into Dictionary 2. This may be accomplished by making a key known as “identify” in my_dict and assigning my_dict1 dictionary to it. Right here’s tips on how to do it:

my_dict = {"username": "ABC", "e-mail": "abc@gmail.com", "location":"Gurgaon"}

my_dict1 = {"firstName" : "Nick", "lastName": "Jonas"}

my_dict["name"] = my_dict1

print(my_dict)

The output is:

{‘username’: ‘ABC’, ’e-mail’: ‘abc@gmail.com’, ‘location’: ‘Gurgaon’, ‘identify’: {‘firstName’: ‘Nick’, ‘lastName’: Jonas}}

As noticed within the output, the important thing ‘identify’ has the dictionary my_dict1. 

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