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Introduction to Dictionary

☞It is a data structure.

☞It is represented by { } curly braces.

☞It is an unordered collection of items.

☞Each item is a key-value pair.

☞Each key map to a value.

☞Each key is separated from its value by a colon (:), the items are separated by commas (,).

☞Keys are unique while values may not be.

☞Keys must be of an immutable data type(string, number or tuple) while values can be of any type.

☞Keys are case-sensitive.

Syntax : 
 
variable_name = { key1 : value1, key2 : value2, ………..keyN : valueN }

☞Creating an empty dictionary :

Example : 
 
D1 = {}            #empty dictionary
print(D1)

D2 = dict()         #empty dictionary
print(D2)
Output : 
 
{}
{}

☞Creating a dictionary:

Example : 
 
D = {10 : [25.6, 35.6], "A" : "hello", (10,20,30) : "Bye" , 45.5 : "Thanks"}
print(D)
Output : 
 
{10: [25.6, 35.6], 'A': 'hello', (10, 20, 30): 'Bye', 45.5: 'Thanks'}

☞Adding an item to the dictionary :

Example : 
 
D = {}
D[12] = "Twelve"
D[15] = "Fifteen"
D[17] = "Seventeen"
print(D)
Output : 
 
{12: 'Twelve', 15: 'Fifteen', 17: 'Seventeen'}

☞Creating copy of the dictionary :

Example : 
 
D = {12: 'Twelve', 15: 'Fifteen' }
A = dict(D)
print(A)
Output : 
 
{12: 'Twelve', 15: 'Fifteen'}

☞Creating a dictionary by passing nested list to dict() function :

Example : 
 
L = [ ['one' , 1] , ['two' , 2] , ['three', 3] ]
A = dict(L)
print(A)
Output : 
 
{'one': 1, 'two': 2, 'three': 3}
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