Python Dictionary With Advanced Examples

Python Dictionary With Advanced Examples

This article entitle Python Dictionary is a continuation of the previous article entitled Python Tuple.

Dictionary in Python is a collection ordered that start from the 3.7 Python version each item stores key-value pairs and these keys are unique identifiers which is associated with each value.

What is a Python dictionary?

In Python, the dictionary is an implementation of the data structure that is well known to be an associative array.

Further, a dictionary consists of a key-value pairs collection and each key-value pair maps each key to its associated array value.

Example

For instance, we want to create and store information about countries and their capitals. That’s the point that we need to create the Python Dictionary with the specific country names as the keys and the capital will be the values.

KeysValues
FranceParis
GermanyBerlin
NorwayOslo
PhilippinesManila
IndiaNew Delhi

Create a Python dictionary

The following is a Python program to create the dictionary.

cityCapital = {"France": "Paris", "Germany": "Berlin", "Norway": "Oslo", "Philippines": "Manila", "India": "New Delhi"}
print(cityCapital)

Output

{'France': 'Paris', 'Germany': 'Berlin', 'Norway': 'Oslo', 'Philippines': 'Manila', 'India': 'New Delhi'}

We can also create a dictionary with different data types lists.

Example

# dictionary with keys and values of different data types
numberKeys = {100: "One Hundred", 200: "Two Hundred", 300: "Three Hundred"}
print(numberKeys)

Output

{100: 'One Hundred', 200: 'Two Hundred', 300: 'Three Hundred'}

Add elements in the Python dictionary

We can add items to a Python dictionary method with the use of the name of the dictionary with the square brackets [] symbol.

Example

cityCapital = {"France": "Paris", "Germany": "Berlin", "Norway": "Oslo", "Philippines": "Manila", "India": "New Delhi"}
print("Initial Dictionary: ",cityCapital)

cityCapital["Qatar"] = "Doha"

print("Updated Dictionary: ",cityCapital)

Output

Initial Dictionary:  {'France': 'Paris', 'Germany': 'Berlin', 'Norway': 'Oslo', 'Philippines': 'Manila', 'India': 'New Delhi'}
Updated Dictionary:  {'France': 'Paris', 'Germany': 'Berlin', 'Norway': 'Oslo', 'Philippines': 'Manila', 'India': 'New Delhi', 'Qatar': 'Doha'}

Update value in Python dictionary

To update an item in the dictionary we can use the curly braces {} and square brackets [] symbol with an associated value with a particular dict key.

Example

studentIdentification = {1111: "Jude", 1112: "Glenn", 1113: "Paul", 1114: "Adones"}
print("Initial Dictionary: ", studentIdentification)

studentIdentification[1112] = "Adones"

print("Updated Dictionary: ", studentIdentification)

Output

Initial Dictionary:  {1111: 'Jude', 1112: 'Glenn', 1113: 'Paul', 1114: 'Adones'}

Updated Dictionary:  {1111: 'Jude', 1112: 'Adones', 1113: 'Paul', 1114: 'Adones'}

Accessing elements in a dictionary in Python

To access the value in the dictionary we use the keys to access the corresponding values.

Example

studentIdentification = {1111: "Jude", 1112: "Glenn", 1113: "Paul", 1114: "Adones"}

print(studentIdentification[1112])
print(studentIdentification[1113])

Output

Glenn
Paul

Removing elements from a dictionary

To remove or delete a key-value pair in the element from a dictionary we can use the (del statement).

Example

studentIdentification = {1111: "Jude", 1112: "Glenn", 1113: "Paul", 1114: "Adones"}

print("Initial Dictionary: ", studentIdentification)

del studentIdentification[1111]

print("Updated Dictionary ", studentIdentification)

Output

Initial Dictionary:  {1111: 'Jude', 1112: 'Glenn', 1113: 'Paul', 1114: 'Adones'}

Updated Dictionary  {1112: 'Glenn', 1113: 'Paul', 1114: 'Adones'}

Iterating through a dictionary

To iterate through each key in the dictionary we can use the (for loop).

Example

# Iterating through a Dictionary
iterate = {1: 5, 3: 19, 5: 65, 7: 78, 9: 111}
for i in iterate:
    print(iterate[i])

Output

5
19
65
78
111

Python dictionary membership test

To test if the existent key is in the dictionary or not we can use the (in) keyword. Take Note that the membership test is for only the keys and not for values in the dictionary elements.

Example

# Membership Test for Dictionary Keys
iterate = {1: 5, 3: 19, 5: 65, 7: 78, 9: 111}

# Output: True
print(1 in iterate) # prints True

print(2 not in iterate) # prints True

# membership tests for key only not value
print(49 in iterate) # prints false

Output

True
True
False

Methods of Python dictionary

The following table below is the list of methods in the dictionary

Function Description
all()It will return True if all the keys in the dictionary are TRUE or the dictionary is empty.
any()It will return TRUE if any key in the dictionary is TRUE and if the dictionary is empty it will return FALSE.
len()It will return the length or the number of items in the dictionary in Python.
sorted()It will return a new set of a sorted list of keys in the dictionary
clear()It will remove all the items or elements from the dictionary
keys()It will return a new set of objects in dictionary keys.
values()It will return a new set of objects in dictionary values.

Summary

In summary, you have read about Python Dictionary. We also discussed in this article what is a Python dictionary, create a dictionary, add elements, update value, access elements, remove elements, iterate through the dictionary, and the methods of a dictionary.

I hope this article could help you a lot to continue pursuing learning this powerful programming language.

If you want to learn more check out my previous and latest articles for more career-changing articles.

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