How to Add Key/Value Pair

Python dictionary is a group sort 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 referred to as hashing to map keys to their related values. They’re a strong knowledge construction that permits you to retailer and manipulate knowledge in a key-value pair format. One frequent process when working with dictionaries is to append new values to an current dictionary. Whereas Python dictionaries don’t have 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 submit, we are going to 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 vital knowledge sort 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 just 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. Due to this fact, the mix 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 are usually not allowed. 
• It gained’t make sense in case you 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 will probably be thought of.
• If a secret’s specified a second time after the creation of a dictionary, then the second time will probably be thought of as it’s going to override the primary time.
• The important thing have to be immutable, that means the info sort could be an integer, string, tuple, boolean, and so forth. Due to this fact, lists or one other dictionary cannot be used as they’re changeable.  

Tips on how to append a component to a key in a dictionary with Python?

Making a Dictionary

In Python, you’ll be able to 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 sorts akin 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 = {'Identify': ‘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: 

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

Dictionary with integer keys

Right here’s methods 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 parts of a dictionary

Key names are used to entry parts 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

Various methodology 

There’s one other methodology referred to as get() that’s used to entry parts from a dictionary. On this methodology, the bottom line 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()
# methodology
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 may delete parts in a dictionary utilizing the ‘del’ key phrase.

The syntax is –

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

Use the next syntax to delete all the dictionary –

del my_dict  # this may delete the dictionary with identify my_dict

One other different 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 examine an instance of the deletion of parts that end in emptying all the dictionary –

my_dict = {"username": "ABC", "electronic mail": "abc@gmail.com", "location":"Gurgaon"}
del my_dict['username']  # it's 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 may delete the dictionarymy_dict
print(my_dict)

The output is:

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

{}

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

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

    print(my_dict)

NameError: identify ‘my_dict’ shouldn’t be outlined

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

The dict.pop() methodology can be used to delete parts from a dictionary. Utilizing the built-in pop() methodology, you’ll be able to simply delete a component based mostly 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’s going to return the default worth. If neither the default worth nor the bottom line is current, it’s going to give an error. 

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

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

The output is:

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

Appending component(s) to a dictionary

It’s simple to append parts 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", "electronic mail": "abc@gmail.com", "location":"Gurgaon"}

my_dict['name']='Nick'

print(my_dict)

The output is:

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

Updating current component(s) in a dictionary

For updating the present parts 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 methods to do it:

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

my_dict["username"] = "XYZ"

print(my_dict)

The output is:

{‘username’: ‘XYZ’, ’electronic 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”, “electronic 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 performed by making a key referred to as “identify” in my_dict and assigning my_dict1 dictionary to it. Right here’s methods to do it:

my_dict = {"username": "ABC", "electronic 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’, ’electronic 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 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 are usually not allowed in dictionaries

2. Tips on how to append a component to a key in a dictionary with Python:

You may append a component to a listing that may 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 may entry parts in a dictionary utilizing their keys like this:

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

You can too use the get() methodology to entry dictionary parts. This methodology returns None if the bottom line 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 component(s) in a dictionary:

You may 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 can too 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 component(s) to a dictionary:

You may 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 component(s) in a dictionary:

You may replace an current component 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 may 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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