Dictionary In Python

 

Dictionary

• Dictionary is an unordered collection of item.

• Dictionary is defined by { } (curly brackets), where a single item/member consist of a Key and a Value, where key and value are connected using colon ( : ), and each item/member is separated by comma( , ).

        Syntax:

                dictionary_name = {key:value, key:value,...}

 #program

 d1 = {1: "Techno Xpresss", 2: 28, 3: 80.72}
 print("d1 : ", d1)
 print("type(d1)", type(d1))

 #output

 d1 :  {1: 'Techno Xpresss', 2: 28, 3: 80.72}
 type(d1) <class 'dict'>

• Indexing is not supported to access item.member in dictionary.

 #program

 d1 = {"Name": "Techno Xpresss", "Age": 28, "Marks": 80.72}
 print("d1 : ", d1)
 print("type(d1)", type(d1))
 print("d1[0]", d1[0])

 #output

 d1 :  {'Name': 'Techno Xpresss', 'Age': 28, 'Marks': 80.72}
 type(d1) <class 'dict'>
 Traceback (most recent call last):
   File "C:/Self_Practice_Er_M_S_Dandyan/Python/Pycharm/xml/main.py", line 6, in <module>
     print("d1[0]", d1[0])
 KeyError: 0

•  Key is used to retrieve value from dictionary, hence Key must be unique.

 #program

 d1 = {"Name": "Techno Xpresss", "Age": 28, "Marks": 80.72}
 print("d1 : ", d1)
 print("type(d1)  : ", type(d1))
 print("d1[Name]  : ", d1["Name"])
 print("d1[Age]   : ", d1["Age"])
 print("d1[Marks] : ", d1["Marks"])

 #output

 d1 :  {'Name': 'Techno Xpresss', 'Age': 28, 'Marks': 80.72}
 type(d1)  :  <class 'dict'>
 d1[Name]  :  Mandeep
 d1[Age]   :  28
 d1[Marks] :  80.72

• Empty dictionary cab be declared.

 #program

 d1 = { }
 print("d1 : ", d1)
 print("type(d1)  : ", type(d1))

 #output

 d1 :  {}
 type(d1)  :  <class 'dict'>

• Dictionary is mutable, hence addition of new value or modification on Existing item can be done.

 #program

 d1 = {"Name": "Techno Xpresss", "Age": 28, "Marks": 80.72}
 print("d1 : ", d1)

 d1["Name"] = "Er M S Dandyan"
 print("d1 : ", d1)

 #output

 d1 :  {'Name': 'Techno Xpresss', 'Age': 28, 'Marks': 80.72}
 d1 :  {'Name': 'Er M S Dandyan', 'Age': 28, 'Marks': 80.72}

• Item of Dictionary can be a Dictionary, List, Tuple, int, float and string.

 #program dictionary as a member

 d1 = {1: {"Name": "Techno Xpresss", "Age": 28, "Marks": 80.72}, 2 : {"Name": "M S Dandyan", "Age": 26, "Marks": 90.72}}
 print("d1 : ", d1)

 print("d1[1]            :", d1[1])
 print("d1[1]['Name']    :", d1[1]['Name'])
 print("d1[1]['Age']     :", d1[1]['Age'])
 print("d1[1]['Marks']   :", d1[1]['Marks'])

 print("d1[2]        :", d1[2])
 print("d1[2]['Name']    :", d1[2]['Name'])
 print("d1[2]['Age']     :", d1[2]['Age'])
 print("d1[2]['Marks']   :", d1[2]['Marks'])

 #output

 d1 :  {1: {'Name': 'Techno Xpresss', 'Age': 28, 'Marks': 80.72}, 2: {'Name': 'M S Dandyan', 'Age': 26, 'Marks': 90.72}}
 d1[1]            : {'Name': 'Techno Xpresss', 'Age': 28, 'Marks': 80.72}
 d1[1]['Name']    : Techno Xpresss
 d1[1]['Age']     : 28
 d1[1]['Marks']   : 80.72
 d1[2]        : {'Name': 'M S Dandyan', 'Age': 26, 'Marks': 90.72}
 d1[2]['Name']    : M S Dandyan
 d1[2]['Age']     : 26
 d1[2]['Marks']   : 90.72

Dictionary have some Built In Methods