INTRODUCTION TO PYTHON DICTIONARIES

Table of Contents

INTRODUCTION

Dictionaries are unordered collection of key value pair
Each key in the dictionary is associated with a value
Each key should be unique but values can be duplicate
Values are searched with the help of corresponding keys
Values can be of simple or complex data type
Dictionaries are mutable. New keys can be inserted and values can be updated.
Dictionaries are enclosed with curly brackets

DICTIONARY DATA TYPE

Dictionaries are enclosed with in curly brackets. Key and values are paired with semi colon. Each key value pair are separated with a comma.

# Dictionary data type example 1

dict_year_count = {2020:100, 2021:200, 2022:300, 2023:400, 2024:500, 2025:600}
print("\nData type of dict_year_count ->", type(dict_year_count))

INTRODUCTION TO PYTHON DICTIONARIES : Output

Data type of dict_year_count -> <class 'dict'>

NUMERIC KEY VALUE PAIR

INTEGER VALUE

# Dictionary data type example 2

dict_year_count = {2020:100, 2021:200, 2022:300, 2023:400, 2024:500, 2025:600}
print("\nList of key value pair of dict_year_count ->", dict_year_count)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_year_count -> {2020: 100, 2021: 200, 2022: 300, 2023: 400, 2024: 500, 2025: 600}

In the above example, key and values both are integer.

FLOATING VALUE

# Dictionary data type example 3

dict_year_count = {2020:10.5, 2021:15.2, 2022:30.7, 2023:25.9, 2024:27.6, 2025:19.4}
print("\nList of key value pair of dict_year_count ->", dict_year_count)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_year_count -> {2020: 10.5, 2021: 15.2, 2022: 30.7, 2023: 25.9, 2024: 27.6, 2025: 19.4}

In the above example, keys are integer and values are floating number.

STRING KEY VALUE PAIR

# Dictionary data type example 4

dict_prog_type = {'A':'Python', 'B':'Java', 'C':'C++', 'D':'PHP', 'E':'XML', 'F':'VB'}
print("\nList of key value pair of dict_prog_type ->", dict_prog_type)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_prog_type -> {'A': 'Python', 'B': 'Java', 'C': 'C++', 'D': 'PHP', 'E': 'XML', 'F': 'VB'}

In the above example, key and value both are string.

MIXED KEY VALUE PAIR

# Dictionary data type example 5

dict_section_count = {'A':100, 'B':200, 'C':300, 'D':400, 'E':500, 'F':600}
print("\nList of key value pair of dict_section_count ->", dict_section_count)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_section_count -> {'A': 100, 'B': 200, 'C': 300, 'D': 400, 'E': 500, 'F': 600}

In the above example, keys are string and values are integer.

# Dictionary data type example 6

dict_section_valid = {'A':True, 'B':True, 'C':False, 'D':True, 'E':False, 'F':True}
print("\nList of key value pair of dict_section_valid ->", dict_section_valid)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_section_valid -> {'A': True, 'B': True, 'C': False, 'D': True, 'E': False, 'F': True}

In the above example, keys are string and values are boolean.

NESTED DICTIONARIES

# Dictionary data type example 7

dict_class_student_list = {'A':100, 'B':[102, 104, 106], 'C':['John', 'Smith', 'Steve'], 'D':(110, 111, 112), 'E':115, 'F':{116:'Tom', 117:'Jerry'}}
print("\nList of key value pair of dict_class_student_list ->", dict_class_student_list)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_class_student_list -> {'A': 100, 'B': [102, 104, 106], 'C': ['John', 'Smith', 'Steve'], 'D': (110, 111, 112), 'E': 115, 'F': {116: 'Tom', 117: 'Jerry'}}

In the above example, we have used multiple complex data type as value. We have used integer list against key B, string list against key C, tuple against D and dictionary against key F.

DUPLICACY IN DICTIONARIES

Keys in the dictionaries can not be duplicate. But values can be duplicate. In case if we try to use duplicate keys in the dictionaries then python will use the last key value pair and others will be removed..

# Dictionary data type example 8

dict_section_count = {'A':100, 'B':200, 'C':300, 'D':400, 'E':500, 'F':600, 'C':700}
print("\nList of key value pair of dict_section_count ->", dict_section_count)

dict_year_count = {2020:100, 2021:200, 2022:300, 2023:400, 2024:500, 2025:600, 2023:700}
print("\nList of key value pair of dict_year_count ->", dict_year_count)

INTRODUCTION TO PYTHON DICTIONARIES : Output

List of key value pair of dict_section_count -> {'A': 100, 'B': 200, 'C': 700, 'D': 400, 'E': 500, 'F': 600}

List of key value pair of dict_year_count -> {2020: 100, 2021: 200, 2022: 300, 2023: 700, 2024: 500, 2025: 600}

In the above example, we have used duplicate key C for dictionary dict_section_count. But python has taken the last duplicate key that’s why the output is showing C:700. Similarly, we have used duplicate key 2023 for dictionary dict_year_count, but python has taken the last key value pair and output is showing 2023:700.

INTRODUCTION TO PYTHON DICTIONARIES : Output

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INTRODUCTION TO PYTHON DICTIONARIES