Python dictionary append: Tips on how to add Key-value Pair?

Dictionary in Python

A dictionary is a vital knowledge sort in Python programming. It’s a assortment of information values which are unordered. Python dictionary is used to retailer objects by 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. In contrast to different objects, the dictionary merely shops a key together with its worth. Due to this fact, the mixture of a key and its subsequent worth represents a single factor 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 gained’t make sense if you happen to 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 key’s specified a second time after the creation of a dictionary, then the second time will probably be thought of as it is going to override the primary time.
• The important thing should be immutable, which implies that the information sort could be an integer, string, tuple, boolean, and so on. Due to this fact, lists or one other dictionary can’t 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 possibly can create a dictionary simply utilizing mounted 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 could be repeated however can’t 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 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 components of a dictionary

Key names are used to entry components 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 show
# 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 components from a dictionary. On this technique, the hot button is accepted as an argument and returned with a worth. 

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 factor(s) in a dictionary

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

The syntax is –

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

Use the next syntax to delete the whole dictionary –

del my_dict  # this may 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 components that lead to emptying the whole dictionary –

my_dict = {"username": "ABC", "e mail": "[email protected]", "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 may delete the dictionarymy_dict
print(my_dict)

The output is:

{’e mail’: ‘[email protected]’, ‘location’: ‘Gurgaon’}

{}

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

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

    print(my_dict)

NameError: identify ‘my_dict’ shouldn’t be outlined

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

The dict.pop() technique can be used to delete components from a dictionary. Utilizing the built-in pop() technique, you possibly can simply delete a component primarily based 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 hot button 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": "[email protected]", "location":"Gurgaon"}
my_dict.pop("username")
print(my_dict)

The output is:

{’e mail’: ‘[email protected]’, ‘location’: ‘Gurgaon’}

Appending factor(s) to a dictionary

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

Right here’s an instance:

my_dict = {"username": "ABC", "e mail": "[email protected]", "location":"Gurgaon"}

my_dict['name']='Nick'

print(my_dict)

The output is:

{‘username’: ‘ABC’, ’e mail’: ‘[email protected]’, ‘location’: ‘Gurgaon’, ‘identify’: ‘Nick’}

Updating present factor(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 are going to replace the username from ABC to XYZ. Right here’s the way to do it:

my_dict = {"username": "ABC", "e mail": "[email protected]", "location":"Gurgaon"}

my_dict["username"] = "XYZ"

print(my_dict)

The output is:

{‘username’: ‘XYZ’, ’e mail’: ‘[email protected]’, ‘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 beneath –

Dictionary 1:

my_dict = {“username”: “ABC”, “e mail”: “[email protected]”, “location”:”Gurgaon”}

Dictionary 2:

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

Now we need 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 the way to do it:

my_dict = {"username": "ABC", "e mail": "[email protected]", "location":"Gurgaon"}

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

my_dict["name"] = my_dict1

print(my_dict)

The output is:

{‘username’: ‘ABC’, ’e mail’: ‘[email protected]’, ‘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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