Python dictionary is the collection of unordered changeable indexed represented by curly braces, having keys and values.

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Create a dictionary

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
print(dict)

Here the key names are “brand”, “model”, “year” and the corresponding key values are “Realme”, “X50 pro”, “2020”

Accessing Items

To access items we use the get() method.

x = dict.get("year") #returns 2020

Change Values

By referring to the key names we can change the values.

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
print(dict)
dict["year"]=2022
print(dict)

Dictionary Length

We use the len() method for this purpose

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
print(len(dict)) #returns 3

Adding Items

Adding an item to the dictionary is done by using a new index key and assigning a value to it:

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
print(dict)
dict["RAM"]="6 GB"
print(dict)

Removing Items

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
dict.pop("year")
print(dict) # returns {'brand': 'Realme', 'model': 'X50 pro'}

In the above code, we use pop() method for removing key.

dict = {
   "brand": "Realme",
   "model": "X50 pro",
   "year": 2020
 }
 dict.popitem()
 print(dict) #returns {'brand': 'Realme', 'model': 'X50 pro'}

If no key name is mentioned the method popitem() will remove the last inserted item.

del() method as well as clear() method completely delete the dictionary

Loop Through a Dictionary

Method to returns the key name is for loop

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
for i in dict:
   print(i)

Method to print the key values is :

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
for i in dict:
   print(dict[i])

In order to determine both key name and values, the method item() is used.

dict = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
for x, y in dict.items():
  print(x, y)

Copy a Dictionary

You cannot copy a dictionary simply by typing  dict2() = dict1(), because: 

dict2()  will only be a reference to  dict1(), and changes made in dict1()  will automatically also be made in dict2(). The built-in method is copy().

dict1 = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
mydict = dict1.copy()
print(mydict)

The built-in method() is used in Python dictionary is dict()

dict1 = {
  "brand": "Realme",
  "model": "X50 pro",
  "year": 2020
}
mydict = dict(dict1)
print(mydict)

Nested Dictionaries

A dictionary that consists of many dictionaries within it is known as a nested dictionary.

products = {
  "phone1" : {
    "brand" : "Realme",
    "year" : 2020
  },
  "phone2" : {
    "brand" : "HONOR 8x",
    "year" : 2019
  },
  "phone3" : {
    "name" : "Redmi Note 5 pro",
    "year" : 2017
  }
}
print(products)

The dict() Constructor

It is also possible to use the dict() constructor to make a new dictionary:

thisdict = dict(brand="Ford", model="Mustang", year=1964)
print(thisdict)

Dictionary Methods

Python has so many Python built-in methods. They are:

• clear()
• copy()
• gets()
• items()
• keys()
• pop()
• popitem()
• setdefault()
• update()
• values()