Methods to Add Key/Worth Pair

Python dictionary is a group kind that shops knowledge in key-value pairs. It’s unordered, changeable, and doesn’t permit duplicates. Dictionaries are very environment friendly for wanting up and inserting knowledge, as they use a method known as hashing to map keys to their related values. They’re a strong knowledge construction that lets you retailer and manipulate knowledge in a key-value pair format. One widespread job when working with dictionaries is to append new values to an present dictionary. Whereas Python dictionaries shouldn’t have an append() technique like lists do, a number of methods exist so as to add new key-value pairs to a dictionary. On this weblog publish, we’ll discover a few of these strategies and talk about when to make use of every one. So, let’s dive in!

Dictionary in Python

A dictionary is a obligatory knowledge kind in Python programming. It’s a assortment of information values which are unordered. Python dictionary is used to retailer objects 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 prevailing 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 aspect within the Python dictionary.  

Restrictions on Key Dictionaries

Under are enlisted some restrictions on the important thing dictionaries –

• A given key seems solely as soon as in a dictionary. Duplicates of keys should not allowed. 
• It received’t make sense for those who 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 will probably be thought of.
• If a secret is specified a second time after the creation of a dictionary, then the second time will probably be thought of as it would override the primary time.
• The important thing have to be immutable, which means the info kind could 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 parts is positioned inside curly brackets, and key: values are separated by commas. It have to be famous that the worth of keys could be repeated however cannot have duplicates. Additionally, keys ought to have immutable knowledge varieties similar 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 using Integer Keys: ")
print(Dict)
  
# Making a Dictionary
# with Combined keys
Dict = {'Title': ‘Nice Studying’, 1: [1, 2, 3, 4]}
print("nDictionary with using Combined Keys: ")
print(Dict)

The output is :

Dictionary with using Integer Keys: 

{1: ‘Studying’, 2: ‘For’, 3: ‘Life’}

Dictionary with using Combined Keys: 

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

Dictionary with integer keys

Right here’s the way 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.objects():
    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 parts of a dictionary

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

Right here’s an instance –

# Python program to display
# 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

Various technique 

There’s one other technique known as get() that’s used to entry parts from a dictionary. On this technique, the hot button 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 aspect(s) in a dictionary

You possibly can delete parts in a dictionary utilizing the ‘del’ key phrase.

The syntax is –

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

Use the next syntax to delete the complete 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 test an instance of the deletion of parts that lead to emptying the complete dictionary –

my_dict = {"username": "ABC", "e-mail": "abc@gmail.com", "location":"Gurgaon"}
del my_dict['username']  # it would 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’ shouldn’t be outlined

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

The dict.pop() technique can also be used to delete parts 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 would return the default worth. If neither the default worth nor the hot button is current, it would give an error. 

Right here’s an instance that exhibits the deletion of parts 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 aspect(s) to a dictionary

It’s simple to append parts to the prevailing 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 present aspect(s) in a dictionary

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

On this instance, we’ll replace the username from ABC to XYZ. Right here’s the way 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 think about an instance with two dictionaries – Dictionary 1 and Dictionary 2 as proven beneath –

Dictionary 1:

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

Dictionary 2:

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

Now we need to merge Dictionary 1 into Dictionary 2. This may be achieved by making a key known as “identify” in my_dict and assigning my_dict1 dictionary to it. Right here’s the way 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. 

Fast Packages on Python Dictionary Append

1. Restrictions on Key Dictionaries:

Python dictionaries have some restrictions on their keys. Listed below are some examples of invalid dictionary keys:

bashCopy codemy_dict = {[1,2]: 'worth'}  # Lists are unhashable and can't be used as keys
my_dict = {{1:2}: 'worth'}  # Dictionaries are unhashable and can't be used as keys
my_dict = {'a': 'value1', 'a': 'value2'}  # Duplicate keys should not allowed in dictionaries

2. Methods to append a component to a key in a dictionary with Python:

You possibly can append a component to an inventory that could be a worth related to a key in a dictionary like this:

cssCopy codemy_dict = {'key': [1, 2, 3]}
my_dict['key'].append(4)
print(my_dict)  # Output: {'key': [1, 2, 3, 4]}

3. Accessing parts of a dictionary:

You possibly can entry parts in a dictionary utilizing their keys like this:

bashCopy codemy_dict = {'key1': 'value1', 'key2': 'value2'}
print(my_dict['key1'])  # Output: 'value1'

You may also use the get() technique to entry dictionary parts. This technique returns None if the hot button is not current within the dictionary:

bashCopy codemy_dict = {'key1': 'value1', 'key2': 'value2'}
print(my_dict.get('key1'))  # Output: 'value1'
print(my_dict.get('key3'))  # Output: None

4. Deleting aspect(s) in a dictionary:

You possibly can delete a component from a dictionary utilizing the del key phrase like this:

cssCopy codemy_dict = {'key1': 'value1', 'key2': 'value2'}
del my_dict['key1']
print(my_dict)  # Output: {'key2': 'value2'}

5. Deleting Factor(s) from dictionary utilizing pop() technique:

You may also delete a component from a dictionary utilizing the pop() technique. This technique removes the key-value pair from the dictionary and returns the worth:

goCopy codemy_dict = {'key1': 'value1', 'key2': 'value2'}
worth = my_dict.pop('key1')
print(my_dict)  # Output: {'key2': 'value2'}
print(worth)  # Output: 'value1'

6. Appending aspect(s) to a dictionary:

You possibly can append a brand new key-value pair to a dictionary like this:

cssCopy codemy_dict = {'key1': 'value1'}
my_dict['key2'] = 'value2'
print(my_dict)  # Output: {'key1': 'value1', 'key2': 'value2'}

7. Updating present aspect(s) in a dictionary:

You possibly can replace an present aspect in a dictionary by assigning a brand new worth to its key like this:

cssCopy codemy_dict = {'key1': 'value1', 'key2': 'value2'}
my_dict['key2'] = 'new_value'
print(my_dict)  # Output: {'key1': 'value1', 'key2': 'new_value'}

8. Insert a dictionary into one other dictionary:

You possibly can insert a dictionary into one other dictionary through the use of the replace() technique like this:

bashCopy codemy_dict1 = {'key1': 'value1'}
my_dict2 = {'key2': 'value2'}
my_dict1.replace(my_dict2)
print(my_dict1)  # Output:

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