Python dictionary append: How to add Key-value Pair?

Dictionary in Python

A dictionary is a crucial data type in Python programming. It’s a assortment of information values which might be unordered. Python dictionary is used to retailer gadgets through 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. Due to this fact, the mix 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 aren’t allowed. 
• It received’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 might be thought-about.
• If a key’s specified a second time after the creation of a dictionary, then the second time might be thought-about as it’ll override the primary time.
• The important thing have to be immutable, which signifies that the information kind will be an integer, string, tuple, boolean, and so on. Due to this fact, lists or one other dictionary cannot be used as they’re changeable.  

Find out 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 will be repeated however cannot have duplicates. Additionally, keys ought to have immutable information 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 find out 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 parts of a dictionary

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

Right here’s an instance –

# Python program to reveal
# 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 methodology 

There’s one other methodology known as get() that’s used to entry parts from a dictionary. On this methodology, 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()
# 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 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 whole dictionary –

del my_dict  # it will delete the dictionary with identify my_dict

One other different is to make use of the clear() methodology. This methodology helps to wash 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 end in emptying the whole dictionary –

my_dict = {"username": "ABC", "e mail": "abc@gmail.com", "location":"Gurgaon"}
del my_dict['username']  # it'll 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 “major.py”, line 7, in <module>

    print(my_dict)

NameError: identify ‘my_dict’ isn’t outlined

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

The dict.pop() methodology can also be used to delete parts from a dictionary. Utilizing the built-in pop() methodology, you’ll be able to 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’ll return the default worth. If neither the default worth nor the hot button is current, it’ll give an error. 

Right here’s an instance that reveals 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 straightforward 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 are going to replace the username from ABC to XYZ. Right here’s find out 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 think about 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 find out 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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