How to Add Key/Value Pair

Python dictionary is a group kind that shops information in key-value pairs. It’s unordered, changeable, and doesn’t permit duplicates. Dictionaries are very environment friendly for wanting up and inserting information, as they use a method known as hashing to map keys to their related values. They’re a strong information construction that means that you can retailer and manipulate information in a key-value pair format. One frequent job when working with dictionaries is to append new values to an current dictionary. Whereas Python dictionaries do not need an append() methodology 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 crucial information kind in Python programming. It’s a assortment of knowledge values which might be unordered. Python dictionary is used to retailer gadgets during which 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 mix of a key and its subsequent worth represents a single aspect 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 will not be allowed. 
• It gained’t make sense for those who map a selected 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 can be thought-about.
• If a secret’s specified a second time after the creation of a dictionary, then the second time can be thought-about as it should override the primary time.
• The important thing should be immutable, that means the info kind may be an integer, string, tuple, boolean, and so on. Subsequently, lists or one other dictionary cannot be used as they’re changeable.  

The way to append a component to a key in a dictionary with Python?

Making a Dictionary

In Python, you possibly can 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 information sorts corresponding 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 Combined keys
Dict = {'Title': ‘Nice Studying’, 1: [1, 2, 3, 4]}
print("nDictionary with the usage of Combined Keys: ")
print(Dict)

The output is :

Dictionary with the usage of Integer Keys: 

{1: ‘Studying’, 2: ‘For’, 3: ‘Life’}

Dictionary with the usage of 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.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 is advisable 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', 'title': '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 methodology 

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

Right here’s an instance –

# Making a Dictionary
Dict = {1: 'Studying', 'title': 'For', 3: 'Life'}
  
# accessing a component utilizing get()
# methodology
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’ll be able to delete components in a dictionary utilizing the ‘del’ key phrase.

The syntax is –

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

Use the next syntax to delete your complete dictionary –

del my_dict  # it will delete the dictionary with title my_dict

One other various is to make use of the clear() methodology. This methodology 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 components that end in emptying your complete dictionary –

my_dict = {"username": "ABC", "e mail": "abc@gmail.com", "location":"Gurgaon"}
del my_dict['username']  # it should take away "username": "ABC" from my_dict
print(my_dict)
my_dict.clear()  # until will make the dictionarymy_dictempty
print(my_dict)
delmy_dict # it will 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: title ‘my_dict’ shouldn’t be outlined

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

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

dict.pop(key, defaultvalue)

The pop() methodology returns the worth of the eliminated key. In case of the absence of the given key, it should return the default worth. If neither the default worth nor the secret’s current, it should 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 aspect(s) to a dictionary

It’s straightforward to append components to the prevailing dictionary utilizing the dictionary title 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’, ‘title’: ‘Nick’}

Updating current aspect(s) in a dictionary

For updating the prevailing components 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 executed by making a key known as “title” 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’, ‘title’: {‘firstName’: ‘Nick’, ‘lastName’: Jonas}}

As noticed within the output, the important thing ‘title’ 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 here 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 will not be allowed in dictionaries

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

You’ll be able to 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 components of a dictionary:

You’ll be able to entry components in a dictionary utilizing their keys like this:

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

You too can use the get() methodology to entry dictionary components. This methodology returns None if the secret’s 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’ll be able to 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 Ingredient(s) from dictionary utilizing pop() methodology:

You too can delete a component from a dictionary utilizing the pop() methodology. This methodology 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’ll be able to 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 current aspect(s) in a dictionary:

You’ll be able to replace an current 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’ll be able to insert a dictionary into one other dictionary by utilizing the replace() methodology like this:

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

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