Python Dictionaries

A “dictionary” is a collection which is unordered, mutable & indexed.
In Python, dictionaries are indicated with curly brackets { }, and they have pair of

keys and values.

Why use Dictionary?

In dictionary, we can keep the elements in key-value mapping arrangement.
Internally uses hashing for accessing the key value pair, so we can locate elements using key very quickly.

key : value (pairing)

#creating dictionary and printing content and type
my_dict  = {
  "id": 1,
  "name": "Hello World",
  "year": 2020
}
print(my_dict)
print(type(my_dict))

#Output: {'id': 1, 'name': 'Hello World', 'year': 2020}
#<class 'dict'>

Accessing Items

my_dict  = {
  "id": 1,
  "name": "Hello World",
  "year": 2020
}
# accessing dictionary key- name
name = my_dict["name"]
print(name)

Accessing Items using get()

my_dict  = {
  "id": 1,
  "name": "Hello World",
  "year": 2020
}
# accessing dictionary element
name = my_dict.get("name")
print(name)

Dictionary fromkeys() method

The fromkeys() method creates a new dictionary from the given sequence of elements with a value provided by the user.

x = ('key1', 'key2', 'key3')
y = 0

thisdict = dict.fromkeys(x, y)

print(thisdict)

#output- ['key1': 0, 'key2': 0, 'key3': 0]

Keys () and values () methods

#The keys and values methods are used to return lists containing the dictionaries keys and values respectively

car = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}

x = car.keys()
print(x)

#output- [brand, model, year]
car = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}

x = car.values()
print(x)

#output- [Ford, Mustang, 1964]