Python Dictionary:

A dictionary is a collection of items which is not in order, changeable and are indexed.

In Python dictionary are written with curly brackets and they have keys and values.

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

print(dict1)

Output:

{'brand': 'BMW', 'color': 'Red', 'year': '2009'}

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Accessing Items in dict:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

x = dict1["brand"]

print(x)

Output:
BMW

Note: Here we have access item with the help of their key name.

Note: In above example, you can also use (x = dict1.get["brand"]) instead of 
(x = dict1["brand"])

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Changing values in dict:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

dict1["year"] = 2019

print(x) 

Output:

{'brand': 'BMW', 'color': 'Red', 'year': '2019'}

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For loop through a dict:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

for x in dict1:

       print(x) 

Output:

brand

color

year

To print all values of dictionary:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

for x in dict1:

       print(dict1[x]) 

Output:

BMW

Red

2019

Note: In above example,we can use [for x in dict1.values()] instead of 

[for x in dict1].

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To print both key and value:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

for x,y in dict1.items():

       print(x,y) 

Output:

brand BMW

color Red

year 2019

---

Dictionary Length:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

print(len(dict1))

Output:
3

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Adding Items to dict:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}
dict1['speed'] = "fast"

print(dict1)

Output:

{'brand': 'BMW', 'color': 'Red', 'year': '2009', 'speed': 'fast'}

---

Removing Items from dict:

pop() method is used to remove item.

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

dict1.pop("color")

print(dict1)

Output:

{'brand': 'BMW', 'year': '2009'}

Note: we can also use (del dict1["color"]) instead of [dict1.pop("color")] to remove specific key.

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clear( ) method:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

dict1.clear()

print(dict1)

Output:

{}

Note: clear() method clear the dictionary.

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Copy a Dictionary:

copy() method is used to copy a dictionary into another.

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

dict2 = dict1.copy()

print(dict2)

Output:

{'brand': 'BMW', 'color': 'Red', 'year': '2009'}

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dict( ) Constructor:

dict() constructor to make a new dictionary.

Example:

dict1 = dict("brand": "BMW","color": "Red","year": 2009)

print(dict1)

Output:

{'brand': 'BMW', 'color': 'Red', 'year': '2009'}

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fromkeys() method:

fromkeys() method returns a dictionary with the specified keys and values.

Example:

x = ('brand', 'color', 'year')
y = ('BMW', 'Red', '2009')

dict1 = dict.fromkeys(x, y)

print(thisdict)

Output:

{'brand': 'BMW', 'color': 'Red',': '2009'}

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keys() method:

Example:

dict1 = {

  "brand": "BMW",

  "color": "Red",

  "year": 2009

}

x = dict1.keys()

print(x)

Output:

('brand', 'color',  'year')

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