Dictionary Python – Nice Studying


Dictionaries in Python come tremendous useful as they allow you to retailer and manage knowledge in a versatile approach. Consider it as a real-life dictionary the place you possibly can seek for phrases and discover their meanings. With dictionaries, you possibly can affiliate “keys” with “values.”  The keys are just like the phrases you’re trying up, and the values are the meanings that go together with these phrases. 

Dictionaries present quick and environment friendly knowledge retrieval primarily based on keys. Python makes use of hashing to shortly find the worth related to a given key, making dictionaries perfect for accessing particular knowledge shortly. Secondly, dictionaries help you manage and construction your knowledge logically. Moreover, you get a concise and readable technique to symbolize complicated relationships and mappings between totally different entities. 

Let’s study extra about creating, accessing, modifying, and updating dictionaries together with their operations and comprehensions. We’ll additionally study nested dictionaries, dictionary manipulation strategies, built-in capabilities and a lot extra.

Creating and Accessing Dictionaries

Let’s dive into creating and accessing dictionaries in Python. 

Dictionary Syntax and Construction

Dictionaries are outlined utilizing curly braces ({}) and include key-value pairs. The important thing-value pairs are separated by colons (:) and particular person pairs are separated by commas. The keys may be any immutable knowledge sort, corresponding to strings, numbers, or tuples, whereas the values may be any knowledge sort, together with lists, strings, numbers, and even different dictionaries.

Dictionary Creation and Initialization

Let’s say we wish to create a dictionary to retailer the ages of various folks. Right here’s the right way to do it:

ages = {"Alice": 25, "Bob": 30, "Charlie": 35}

Right here, we’ve a dictionary referred to as ages with three key-value pairs. The keys are the names of individuals, and the corresponding values are their ages.

Accessing Values Utilizing Keys

To entry the values in a dictionary, you should use the keys because the “index” to retrieve the related values. Let’s proceed with our ages dictionary instance:

print(ages["Alice"])  # Output: 25

print(ages["Bob"])    # Output: 30

print(ages["Charlie"])# Output: 35

Through the use of the respective keys in sq. brackets, we will entry the values related to these keys. On this case, we retrieve the ages of Alice, Bob, and Charlie.

Dealing with Lacking Keys and Default Values

Generally, it’s possible you’ll must deal with conditions the place a key doesn’t exist in a dictionary. To keep away from errors, you should use the get() technique or conditional statements. The get() technique lets you specify a default worth to return if the secret’s not discovered:

print(ages.get(“Dave”, “Unknown”))  # Output: Unknown

Right here, the important thing “Dave” doesn’t exist within the age dictionary. Through the use of get(), we offer a default worth of “Unknown” to be returned as an alternative.

Alternatively, you should use conditional statements to examine if a key exists in a dictionary earlier than accessing its worth:

if “Alice” in ages:

    print(ages["Alice"])  # Output: 25


    print("Alice's age shouldn't be out there.")

Right here, we examine if the important thing “Alice” is current within the ages dictionary earlier than accessing its worth. If the important thing exists, we print the related age; in any other case, we show a message indicating that the age shouldn’t be out there.

Modifying and Updating Dictionaries

Let’s discover ways to modify and replace dictionaries.

Including and Eradicating Key-Worth Pairs

Dictionaries are mutable, which means you possibly can modify them by including or eradicating key-value pairs. So as to add a brand new key-value pair, you possibly can merely assign a price to a brand new or current key:

pupil = {"title": "Alice", "age": 25}

pupil["grade"] = "A"

Right here, we’ve a dictionary referred to as pupil with two key-value pairs. We then add a brand new key referred to as “grade” and assign the worth “A” to it. The dictionary now has three key-value pairs.

To take away a key-value pair, you should use the del key phrase adopted by the dictionary title and the important thing you wish to take away:

del pupil["age"]

Right here, we take away the important thing “age” and its related worth from the scholar dictionary. After this, the dictionary solely incorporates the “title” and “grade” key-value pairs.

Updating Values for Present Keys

If you wish to replace the worth of an current key in a dictionary, you possibly can merely reassign a brand new worth to that key:

pupil["grade"] = "A+"

Right here, we replace the worth of the “grade” key to “A+”. The dictionary is modified to replicate the up to date worth for the important thing.

Merging Dictionaries utilizing the replace() Methodology

You may merge the contents of two dictionaries into one by utilizing the replace() technique. Let’s say we’ve two dictionaries, dict1 and dict2, and we wish to merge them into a brand new dictionary referred to as merged_dict:

dict1 = {"a": 1, "b": 2}

dict2 = {"c": 3, "d": 4}

merged_dict = {}



Right here, we create an empty dictionary referred to as merged_dict after which use the replace() technique so as to add the key-value pairs from dict1 and dict2. After executing this code, merged_dict will comprise all of the key-value pairs from each dict1 and dict2.

Widespread Dictionary Operations and Strategies

By mastering these widespread operations and strategies, you’ll be outfitted to work effectively with dictionaries in Python. Whether or not it is advisable to iterate over objects, examine for key existence, extract keys or values, or discover the size of a dictionary, these strategies will show helpful in varied programming eventualities.

Iterating over Dictionary Gadgets

It lets you entry each the keys and their corresponding values. You should utilize a loop, corresponding to a for loop, to iterate over the objects. Right here’s an instance:

pupil = {"title": "Alice", "age": 25, "grade": "A"}

for key, worth in pupil.objects():

    print(key, worth)

Right here, we iterate over the objects of the scholar dictionary utilizing the objects() technique. Throughout the loop, we entry every key-value pair and print them. This lets you carry out operations on every merchandise or extract particular info from the dictionary.

Checking for the Existence of Keys

Generally, it’s possible you’ll must examine if a selected key exists in a dictionary. You should utilize the in key phrase to carry out this examine. Let’s see an instance:

pupil = {"title": "Alice", "age": 25, "grade": "A"}

if "age" in pupil:

    print("Age exists within the dictionary.")


    print("Age doesn't exist within the dictionary.")

Right here, we examine if the important thing “age” exists within the pupil dictionary utilizing the in key phrase. If the secret’s current, we print a message indicating its existence; in any other case, we print a message indicating its absence.

Getting Keys, Values, or Each from a Dictionary

There are helpful strategies out there to extract keys, values, or each from a dictionary. Listed below are some examples:

pupil = {"title": "Alice", "age": 25, "grade": "A"}

keys = pupil.keys()

values = pupil.values()

objects = pupil.objects()

print(keys)   # Output: dict_keys(['name', 'age', 'grade'])

print(values) # Output: dict_values(['Alice', 25, 'A'])

print(objects)  # Output: dict_items([('name', 'Alice'), ('age', 25), ('grade', 'A')])

Right here, we use the keys(), values(), and objects() strategies to acquire the keys, values, and key-value pairs as separate objects. These strategies return particular views that help you entry the dictionary’s keys, values, or objects in a handy approach.

Discovering the Size of a Dictionary

To find out the variety of key-value pairs in a dictionary, you should use the len() operate. Right here’s an instance:

pupil = {"title": "Alice", "age": 25, "grade": "A"}

size = len(pupil)

print(size)  # Output: 3

Right here, we calculate the size of the scholar dictionary utilizing the len() operate. The operate returns the variety of key-value pairs within the dictionary.

Dictionary Comprehensions

Dictionary comprehensions are a concise and environment friendly technique to create dictionaries in Python. They observe the same idea to checklist comprehensions however help you create dictionaries with key-value pairs in a single line of code. Dictionary comprehensions present a clear and readable syntax for producing dictionaries primarily based on particular situations or transformations.

Creating Dictionaries Utilizing Comprehensions

To create a dictionary utilizing a comprehension, it is advisable to outline the key-value pairs inside curly braces ({}) and specify the key-value expression. 

squares = {x: x**2 for x in vary(1, 6)}

Right here, we create a dictionary referred to as squares utilizing a comprehension. The expression x: x**2 represents the key-value pairs, the place the secret’s x and the worth is x**2. We iterate over a spread from 1 to six and generate key-value pairs the place the keys are the numbers and the values are their squares. The ensuing dictionary will seem like this: {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}.

Benefits and Use Instances of Dictionary Comprehensions:

Dictionary comprehensions supply a number of benefits and can be utilized in varied eventualities, corresponding to:

  • Concise and Readable Code: Dictionary comprehensions allow you to categorical complicated logic or transformations in a single line of code, bettering code readability and making your intentions clear.
  • Filtering and Transformation: It may be used to filter or modify knowledge. This allows you to create dictionaries primarily based on particular necessities.
  • Environment friendly Information Era: You may generate dictionaries effectively, decreasing the quantity of code and bettering efficiency.
  • Information Restructuring: Dictionary comprehensions are useful when it is advisable to restructure knowledge from one format to a different. You may map current keys to new values and even swap keys and values inside the comprehension.

Nested Dictionaries

A nested dictionary is a dictionary that incorporates one other dictionary (or dictionaries) as its values. This enables for a hierarchical construction, the place you possibly can manage and retailer associated knowledge inside the nested ranges. In different phrases, the values of a dictionary may be dictionaries themselves.

Accessing and Modifying Values in Nested Dictionaries

To entry values in a nested dictionary, you should use a number of sq. brackets to specify the keys at every degree. Right here’s an instance:

college students = {

    "Alice": {

        "age": 25,

        "grade": "A"


    "Bob": {

        "age": 30,

        "grade": "B"



print(college students["Alice"]["age"])  # Output: 25

Right here, we’ve a dictionary referred to as college students, the place every key represents a pupil’s title, and the corresponding worth is a nested dictionary containing the scholar’s age and grade. Through the use of a number of sq. brackets, we will entry particular values inside the nested ranges.

To change values in a nested dictionary, you possibly can observe the same strategy. For instance:

college students["Alice"]["grade"] = "A+"

Right here, we replace the worth of the “grade” key for the scholar named “Alice” to “A+”. This modification applies on to the nested dictionary inside the principle dictionary.

Examples of Nested Dictionary

Nested dictionaries may be helpful in varied eventualities. Listed below are just a few examples:

  • Managing Pupil Data: You should utilize a nested dictionary construction to retailer pupil info, corresponding to names, ages, and grades. Every pupil’s particulars may be represented by a nested dictionary inside the principle dictionary.
  • Organizing Stock Information: If you happen to’re engaged on a listing administration system, nested dictionaries may be useful for organizing product particulars. Every product can have its personal dictionary containing attributes like title, value, amount, and so on.
  • Storing Multi-Stage Configuration Settings: When coping with configuration settings, you might have a number of ranges of settings, corresponding to sections and subsections. A nested dictionary can symbolize this hierarchical construction, permitting you to entry and modify settings at totally different ranges simply.

Dictionary Manipulation Methods

Let’s discover some useful strategies for manipulating dictionaries in Python.

Sorting Dictionaries by Keys or Values

Python supplies handy strategies to kind dictionaries primarily based on both their keys or values. Listed below are a few examples:

To kind a dictionary by its keys, you should use the sorted() operate together with the keys() technique. Right here’s an instance:

student_grades = {"Alice": 85, "Bob": 92, "Charlie": 78}

sorted_by_keys = {key: student_grades[key] for key in sorted(student_grades.keys())}

Right here, we create a brand new dictionary referred to as sorted_by_keys by iterating over the keys of the student_grades dictionary in sorted order. This may end in a dictionary with the keys sorted alphabetically: {“Alice”: 85, “Bob”: 92, “Charlie”: 78}.

To kind a dictionary by its values, you should use the sorted() operate with a lambda operate as the important thing parameter. Right here’s an instance:

student_grades = {"Alice": 85, "Bob": 92, "Charlie": 78}

sorted_by_values = {key: worth for key, worth in sorted(student_grades.objects(), key=lambda merchandise: merchandise[1])}

Right here, we create a brand new dictionary referred to as sorted_by_values by sorting the objects of the student_grades dictionary primarily based on their values utilizing a lambda operate. The ensuing dictionary might be sorted in ascending order by values: {“Charlie”: 78, “Alice”: 85, “Bob”: 92}.

Filtering Dictionaries Based mostly on Sure Standards

You may filter dictionaries primarily based on particular standards utilizing conditional statements and dictionary comprehensions. Right here’s an instance:

student_grades = {"Alice": 85, "Bob": 92, "Charlie": 78}

filtered_grades = {key: worth for key, worth in student_grades.objects() if worth >= 80}

Right here, we create a brand new dictionary referred to as filtered_grades by iterating over the objects of the student_grades dictionary and together with solely these with values larger than or equal to 80. The ensuing dictionary will comprise solely the key-value pairs that fulfill the given situation: {“Alice”: 85, “Bob”: 92}.

Making a Dictionary from Two Lists utilizing zip()

You may create a dictionary by combining two lists utilizing the zip() operate. Right here’s an instance:

names = ["Alice", "Bob", "Charlie"]

ages = [25, 30, 28]

combined_dict = {title: age for title, age in zip(names, ages)}

Right here, we use zip() to mix the names and ages lists, after which create a brand new dictionary referred to as combined_dict. Every title from the names checklist turns into key, and every corresponding age from the ages checklist turns into the respective worth within the dictionary: {“Alice”: 25, “Bob”: 30, “Charlie”: 28}.

Dictionary Strategies and Constructed-in Capabilities

Whether or not it is advisable to entry keys, values, or objects, retrieve particular values, take away entries, or carry out basic operations like discovering the size or most/minimal values, these strategies and capabilities have gotten you coated.

Generally Used Dictionary Strategies

  • keys(): It returns a view object that incorporates all of the keys of a dictionary. This lets you entry and iterate over the keys conveniently.
  • values(): It returns a view object that incorporates all of the values of a dictionary. It supplies a technique to entry and iterate over the values saved within the dictionary.
  • objects(): It returns a view object that incorporates all of the key-value pairs of a dictionary as tuples. It lets you entry and iterate over the key-value pairs collectively.
  • get(key, default): It retrieves the worth related to a selected key within the dictionary. If the secret’s not discovered, it returns a default worth as an alternative of elevating an error.
  • pop(key, default): It removes and returns the worth related to a selected key from the dictionary. If the secret’s not discovered, it returns a default worth or raises a KeyError if no default worth is offered.

Constructed-in Capabilities for Dictionaries

  • len(): It returns the variety of key-value pairs in a dictionary. It’s a handy technique to decide the scale or size of a dictionary.
  • max(): It may be used to search out the utmost key or worth in a dictionary, primarily based on their pure ordering. It’s helpful when it is advisable to discover the biggest key or worth in a dictionary.
  • min(): It really works equally to max(), however it finds the minimal key or worth in a dictionary primarily based on their pure ordering.

Superior Dictionary Methods

By understanding these superior strategies, you possibly can broaden your dictionary expertise and use dictionaries extra successfully in Python. 

Dealing with Dictionary Collisions and Hash Capabilities

In Python, dictionaries use hash capabilities to map keys to particular places inside the underlying knowledge construction. Sometimes, two keys might produce the identical hash worth, leading to a collision. Python handles these collisions routinely, however it’s useful to grasp the ideas.

Hash capabilities are answerable for producing hash codes, distinctive identifiers related to every key. Python’s built-in hash operate produces these hash codes. When a collision happens, Python makes use of a way referred to as open addressing or chaining to resolve it.

As a consumer, you don’t want to fret an excessive amount of about dealing with collisions or hash capabilities immediately. Python’s dictionary implementation takes care of this complexity behind the scenes, guaranteeing environment friendly key-value lookups and updates.

Working with Dictionaries as Perform Arguments and Return Values

Dictionaries are versatile knowledge buildings that may be handed as arguments to capabilities and returned as operate outcomes. This enables for versatile and dynamic interactions. 

  • Passing Dictionaries as Perform Arguments:

It allows you to present key-value pairs as inputs. That is significantly helpful when you will have a various variety of arguments or wish to bundle associated knowledge collectively. Capabilities can then entry and make the most of the dictionary’s contents as wanted.

  • Returning Dictionaries from Capabilities:

Capabilities also can return dictionaries as their outcomes. This lets you encapsulate and supply computed or processed knowledge in a structured method. The calling code can then entry and make the most of the returned dictionary to retrieve the specified info.

Working with dictionaries in operate arguments and return values promotes flexibility and modularity in your code. It permits for simple communication of knowledge between totally different elements of your program.

Customizing Dictionaries utilizing OrderedDict and defaultdict

Python supplies further dictionary variants that provide customization past the usual dictionary implementation. Let’s discover two such variants:

The OrderedDict class maintains the order wherein key-value pairs are inserted. Normal dictionaries don’t assure any particular order. Through the use of OrderedDict, you possibly can iterate over the key-value pairs within the order they had been added. This may be useful when order issues, corresponding to preserving the order of components in a configuration or processing steps.

The defaultdict class, out there within the collections module, supplies a default worth for keys that don’t exist within the dictionary. This eliminates the necessity for guide checks to deal with lacking keys. You may specify the default worth when making a defaultdict. That is significantly helpful when working with counters, frequency distributions, or grouping knowledge.

Actual-world Examples and Functions

Let’s discover some real-world examples and functions of dictionaries in Python. 

Information Manipulation

Dictionaries are glorious for organizing and manipulating knowledge. For example, think about you will have a dataset of scholars with their names, grades, and topics. You should utilize dictionaries to symbolize every pupil, the place the title is the important thing and the related values comprise their grade and topics. This lets you simply entry and replace particular person pupil information.

Configuration Settings

Dictionaries are generally used to retailer and handle configuration settings in functions. For example, you possibly can create a dictionary to carry varied settings, such because the database connection particulars, file paths, and consumer preferences. Through the use of key-value pairs, you possibly can simply entry and modify these settings all through your program.

Dictionaries will also be highly effective instruments for fixing programming issues. Listed below are just a few examples:

Counting and Frequency Evaluation

Dictionaries are sometimes employed for counting occurrences and performing frequency evaluation. For example, you should use a dictionary to depend the frequency of phrases in a textual content doc or monitor the incidence of characters in a string, which may be useful for varied textual content processing duties.

Grouping and Categorization

Dictionaries are helpful for grouping and categorizing knowledge primarily based on particular standards. For example, you should use dictionaries to group college students by their grades, staff by departments, or merchandise by classes. This enables for environment friendly knowledge group and retrieval.


Memoization is a way used to optimize operate calls by storing the outcomes of high-priced computations. Dictionaries are sometimes employed as a cache to retailer beforehand computed values. Through the use of the enter arguments as keys and the computed outcomes as values, you possibly can keep away from redundant computations and enhance the efficiency of your code.

Concluding Ideas

We’ve coated varied features of dictionaries in Python, exploring key ideas and demonstrating their sensible functions. We’ve seen the right way to create and entry dictionaries, modify and replace their contents, carry out widespread operations and strategies, make the most of superior strategies, and apply dictionaries to real-world eventualities and programming issues.

By now, you must have a stable understanding of how dictionaries work and their advantages. Nevertheless, there’s all the time extra to study and uncover! Dictionaries supply an unlimited array of potentialities, and we encourage you to proceed exploring and experimenting with them. Strive totally different strategies, mix dictionaries with different knowledge buildings, and apply them to unravel various challenges.


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