new dictionary in python assignment expert

• How it works
• Homework answers

Answer to Question #288912 in Python for sai krishna

New Dictionary

Peter is making a new dictionary. He wants to arrange the words in the ascending order of their length and later arrange the ones with the same length in lexicographic order. Each word is given a serial number according to its position. Find the word according to the serial number.

The serial number of words in Peter's dictionary is as follows

Serial Number

Need a fast expert's response?

and get a quick answer at the best price

for any assignment or question with DETAILED EXPLANATIONS !

Leave a comment

Ask your question, related questions.

• 1. a class of students p gave a science viva their final results are listed out in the order of their r
• 2. A credit card company calculates a customer's "minimum payment" according to the foll
• 3. smallest amoung three numbers input = 6,5, 4 and -1000, - 1000, -1000
• 4. Find the closest pairs (excluding self pairs) on the basis of both the distance measures
• 5. b) Define the find_max_gap function which will take as a parameter a list of values, sort it in asce
• 6. A program is asked to execute a text that is given as a multi-line string, and then returns statisti
• 7. Assume that you have to create such an application for maintaining a database of book titles and the
• Programming
• Engineering

Create a Dictionary in Python – Python Dict Methods

In this article, you will learn the basics of dictionaries in Python.

You will learn how to create dictionaries, access the elements inside them, and how to modify them depending on your needs.

You will also learn some of the most common built-in methods used on dictionaries.

Here is what we will cover:

• Define an empty dictionary
• Define a dictionary with items
• An overview of keys and values 1. Find the number of key-value pairs contained in a dictionary 2. View all key-value pairs 3. View all keys 4. View all values
• Access individual items
• Add new items
• Update items
• Delete items

How to Create a Dictionary in Python

A dictionary in Python is made up of key-value pairs.

In the two sections that follow you will see two ways of creating a dictionary.

The first way is by using a set of curly braces, {} , and the second way is by using the built-in dict() function.

How to Create An Empty Dictionary in Python

To create an empty dictionary, first create a variable name which will be the name of the dictionary.

Then, assign the variable to an empty set of curly braces, {} .

Another way of creating an empty dictionary is to use the dict() function without passing any arguments.

It acts as a constructor and creates an empty dictionary:

How to Create A Dictionary With Items in Python

To create a dictionary with items, you need to include key-value pairs inside the curly braces.

The general syntax for this is the following:

Let's break it down:

• dictionary_name is the variable name. This is the name the dictionary will have.
• = is the assignment operator that assigns the key:value pair to the dictionary_name .
• You declare a dictionary with a set of curly braces, {} .
• Inside the curly braces you have a key-value pair. Keys are separated from their associated values with colon, : .

Let's see an example of creating a dictionary with items:

In the example above, there is a sequence of elements within the curly braces.

Specifically, there are three key-value pairs: 'name': 'Dionysia' , 'age': 28 , and 'location': 'Athens' .

The keys are name , age , and location . Their associated values are Dionysia , 28 , and Athens , respectively.

When there are multiple key-value pairs in a dictionary, each key-value pair is separated from the next with a comma, , .

Let's see another example.

Say that you want to create a dictionary with items using the dict() function this time instead.

You would achieve this by using dict() and passing the curly braces with the sequence of key-value pairs enclosed in them as an argument to the function.

It's worth mentioning the fromkeys() method, which is another way of creating a dictionary.

It takes a predefined sequence of items as an argument and returns a new dictionary with the items in the sequence set as the dictionary's specified keys.

You can optionally set a value for all the keys, but by default the value for the keys will be None .

The general syntax for the method is the following:

Let's see an example of creating a dictionary using fromkeys() without setting a value for all the keys:

Now let's see another example that sets a value that will be the same for all the keys in the dictionary:

An Overview of Keys and Values in Dictionaries in Python

Keys inside a Python dictionary can only be of a type that is immutable .

Immutable data types in Python are integers , strings , tuples , floating point numbers , and Booleans .

Dictionary keys cannot be of a type that is mutable, such as sets , lists , or dictionaries .

So, say you have the following dictionary:

The keys in the dictionary are Boolean , integer , floating point number , and string data types, which are all acceptable.

If you try to create a key which is of a mutable type you'll get an error - specifically the error will be a TypeError .

In the example above, I tried to create a key which was of list type (a mutable data type). This resulted in a TypeError: unhashable type: 'list' error.

When it comes to values inside a Python dictionary there are no restrictions. Values can be of any data type - that is they can be both of mutable and immutable types.

Another thing to note about the differences between keys and values in Python dictionaries, is the fact that keys are unique . This means that a key can only appear once in the dictionary, whereas there can be duplicate values.

How to Find the Number of key-value Pairs Contained in a Dictionary in Python

The len() function returns the total length of the object that is passed as an argument.

When a dictionary is passed as an argument to the function, it returns the total number of key-value pairs enclosed in the dictionary.

This is how you calcualte the number of key-value pairs using len() :

How to View All key-value Pairs Contained in a Dictionary in Python

To view every key-value pair that is inside a dictionary, use the built-in items() method:

The items() method returns a list of tuples that contains the key-value pairs that are inside the dictionary.

How to View All keys Contained in a Dictionary in Python

To see all of the keys that are inside a dictionary, use the built-in keys() method:

The keys() method returns a list that contains only the keys that are inside the dictionary.

How to View All values Contained in a Dictionary in Python

To see all of the values that are inside a dictionary, use the built-in values() method:

The values() method returns a list that contains only the values that are inside the dictionary.

How to Access Individual Items in A Dictionary in Python

When working with lists, you access list items by mentioning the list name and using square bracket notation. In the square brackets you specify the item's index number (or position).

You can't do exactly the same with dictionaries.

When working with dictionaries, you can't access an element by referencing its index number, since dictionaries contain key-value pairs.

Instead, you access the item by using the dictionary name and square bracket notation, but this time in the square brackets you specify a key.

Each key corresponds with a specific value, so you mention the key that is associated with the value you want to access.

The general syntax to do so is the following:

Let's look at the following example on how to access an item in a Python dictionary:

What happens though when you try to access a key that doesn't exist in the dictionary?

It results in a KeyError since there is no such key in the dictionary.

One way to avoid this from happening is to first search to see if the key is in the dictionary in the first place.

You do this by using the in keyword which returns a Boolean value. It returns True if the key is in the dictionary and False if it isn't.

Another way around this is to access items in the dictionary by using the get() method.

You pass the key you're looking for as an argument and get() returns the value that corresponds with that key.

As you notice, when you are searching for a key that does not exist, by default get() returns None instead of a KeyError .

If instead of showing that default None value you want to show a different message when a key does not exist, you can customise get() by providing a different value.

You do so by passing the new value as the second optional argument to the get() method:

Now when you are searching for a key and it is not contained in the dictionary, you will see the message This value does not exist appear on the console.

How to Modify A Dictionary in Python

Dictionaries are mutable , which means they are changeable.

They can grow and shrink throughout the life of the program.

New items can be added, already existing items can be updated with new values, and items can be deleted.

How to Add New Items to A Dictionary in Python

To add a key-value pair to a dictionary, use square bracket notation.

First, specify the name of the dictionary. Then, in square brackets, create a key and assign it a value.

Say you are starting out with an empty dictionary:

Here is how you would add a key-value pair to my_dictionary :

Here is how you would add another new key-value pair:

Keep in mind that if the key you are trying to add already exists in that dictionary and you are assigning it a different value, the key will end up being updated.

Remember that keys need to be unique.

If you want to prevent changing the value of an already existing key by accident, you might want to check if the key you are trying to add is already in the dictionary.

You do this by using the in keyword as we discussed above:

How to Update Items in A Dictionary in Python

Updating items in a dictionary works in a similar way to adding items to a dictionary.

When you know you want to update one existing key's value, use the following general syntax you saw in the previous section:

To update a dictionary, you can also use the built-in update() method.

This method is particularly helpful when you want to update more than one value inside a dictionary at the same time.

Say you want to update the name and age key in my_dictionary , and add a new key, occupation :

The update() method takes a tuple of key-value pairs.

The keys that already existed were updated with the new values that were assigned, and a new key-value pair was added.

The update() method is also useful when you want to add the contents of one dictionary into another.

Say you have one dictionary, numbers , and a second dictionary, more_numbers .

If you want to merge the contents of more_numbers with the contents of numbers , use the update() method.

All the key-value pairs contained in more_numbers will be added to the end of the numbers dictionary.

How to Delete Items from A Dictionary in Python

One of the ways to delete a specific key and its associated value from a dictionary is by using the del keyword.

The syntax to do so is the following:

For example, this is how you would delete the location key from the my_information dictionary:

If you want to remove a key, but would also like to save that removed value, use the built-in pop() method.

The pop() method removes but also returns the key you specify. This way, you can store the removed value in a variable for later use or retrieval.

You pass the key you want to remove as an argument to the method.

Here is the general syntax to do that:

To remove the location key from the example above, but this time using the pop() method and saving the value associated with the key to a variable, do the following:

If you specify a key that does not exist in the dictionary you will get a KeyError error message:

A way around this is to pass a second argument to the pop() method.

By including the second argument there would be no error. Instead, there would be a silent fail if the key didn't exist, and the dictionary would remain unchanged.

The pop() method removes a specific key and its associated value – but what if you only want to delete the last key-value pair from a dictionary?

For that, use the built-in popitem() method instead.

This is general syntax for the popitem() method:

The popitem() method takes no arguments, but removes and returns the last key-value pair from a dictionary.

Lastly, if you want to delete all key-value pairs from a dictionary, use the built-in clear() method.

Using this method will leave you with an empty dictionary.

And there you have it! You now know the basics of dictionaries in Python.

I hope you found this article useful.

To learn more about the Python programming language, check out freeCodeCamp's Scientific Computing with Python Certification .

You'll start from the basics and learn in an interacitve and beginner-friendly way. You'll also build five projects at the end to put into practice and help reinforce what you've learned.

Thanks for reading and happy coding!

Read more posts .

If this article was helpful, share it .

Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started

The ultimate guide to Python Dictionary comprehension

Tabnine Team | 5 min read | July 21, 2021

Python dictionaries — or dict in Python — is a way of storing elements similar to a Python list . However, rather than accessing elements through an index, accessibility is achieved through a pre-assigned fixed key. In a way, a dictionary is like a mini on-site database that can be queried using a “key-value” pair. This method of structuring data lets you create more complex structures and may be more suitable to your needs than a simple, flat, and potentially mutable list.

Dictionaries are something that comes up in spaces like data science, due to their ability to hold multiple dimensions and nested data . In this tutorial, we will go over the following:

• what a Python dictionary is and how to effectively use it
• what Python dictionary comprehension is and why it is an important alternative to loops and lambdas

Without further ado, let’s get started.

What is a Python dictionary and how to use one

A Python dictionary is a collection of items that’s accessible by a specific key rather than an index . This key can be one of the following types:

• floating point
• fronzensets

This is because a Python dictionary key needs to be hashable. Hashing is a process of putting a specific variable through a type of function called a “hash function” to return a unique output.

Here is an example of how to initialize a Python dictionary:

To add to the Python dictionary:

Now, if we print it out:

This will return:

However, if it was a list, we’d use the following syntax:

But this will not work and will return a KeyError . This is because the key 0 doesn’t exist. Querying Python dictionaries is done through the key rather than an index.

Each item in the dictionary can have any data type and isn’t confined to a string as per the example above. It is also good to note that the key has to be unique in a Python dictionary. This means that no duplicates are allowed. However, if there are duplicate keys, Python will not throw an error. Instead, the last instance of the key will be the valid value.

For example:

So when you run print(a['Luxembourg']) , the returned result will be Luxembourg City rather than Western Europe .

And that’s basically creating a Python dictionary in a nutshell.

What is Python Dictionary Comprehension?

Dictionary comprehension is a process of transforming one dictionary into another . The items in the original dictionary can be conditionally included and each item transformed as necessary.

In a way, it’s like copying your original dictionary and doing what you need to do with the values before your final dictionary is set. To do this, you will need to be able to access the key and the value within each dictionary object. This is achievable using .keys() and .values() .

.keys() will return a list of keys contained in your dictionary. For example:

The same is applied to .values() . Here is an example of what it looks like:

Now that you’ve created these lists, you can now pair them up using items() . This will give you access to each key-value pair. Here is an example:

Using keys() , values() and items() sets you up with the ability to create dictionary comprehensions in Python. The general syntax structure for creating a new dictionary is as follows:

For a direct copy of the dictionary through Python dictionary comprehension, here is an example of the syntax:

The first v is representative of any transformations you may want your values to be. You can also make transformations to the key as well by modifying the first instance of the k.

So when we use print(double_dictionary) , we will get the following results:

Why Use Dictionary Comprehension?

As shown in the process above, we don’t have to loop or use lambda functions in order to create copies of a dictionary. During the copying process, dictionary comprehension also lets us create transformations easily.

The thing with loops is that they are used to repeat a block of instructions for a given number of iterations. But things can get complicated for nested loops, which can create confusion and unnecessary complexity.

Dictionary comprehensions are a better alternative to writing loops due to simplification of the ‘looping’ process and therefore readability. For example, rather than writing something like this:

You can simply write the following using Python dictionary comprehension:

Python dictionary comprehension is also a good alternative to lambda functions . A lambda function is a way of creating small anonymous functions. They are considered throwaway functions and are nameless. Their existence only lasts as long as they are needed. lambda functions tend to also include other functions such as filter() , map() , and reduce() to achieve its desired outcome.

For example, let’s create a new dictionary using lambda and map() function.

However, converting Fahrenheit to Celsius is much simpler using a dictionary comprehension. Here is the refactored code:

Overall, there are less lines involved with a dictionary comprehension and informs the developer exactly what the expected end result is to be — another dictionary with the values translated and transformed from the original dictionary.

This is the barebones basics of python dictionary comprehension. The next step is to explore conditions, such as if conditions and using multiple if conditions. Beyond this is nested dictionary comprehension — which poses its challenges due to the nested nature. This is where loops can come into play and help.

Overall, dictionary comprehension is the easiest way to work with sets of data concisely and succinctly . It’s not hard once you get your head around the idea and the techniques above are more than enough to get you started.

The following article is brought to you by Tabnine - an AI-powered tool that uses generative models to improve software development

Get started for free

Related Posts

Tabnine now has over a million users and over 500k active monthly users. As a…

Native apps are all the rage, but web apps are better for accessibility and for…

Digitalization is at the forefront of every industry. As more innovative companies compete to produce…

Learn Python practically and Get Certified .

Popular Tutorials

Popular examples, reference materials, learn python interactively, python introduction.

• Getting Started
• Keywords and Identifier
• Python Comments
• Python Variables

Python Data Types

• Python Type Conversion
• Python I/O and Import
• Python Operators
• Python Namespace

Python Flow Control

• Python if...else
• Python for Loop
• Python while Loop
• Python break and continue
• Python Pass

Python Functions

• Python Function
• Function Argument
• Python Recursion
• Anonymous Function
• Global, Local and Nonlocal
• Python Global Keyword
• Python Modules
• Python Package

Python Datatypes

• Python Numbers
• Python List
• Python Tuple
• Python String

Python Dictionary

Python files.

• Python File Operation
• Python Directory
• Python Exception
• Exception Handling
• User-defined Exception

Python Object & Class

• Classes & Objects
• Python Inheritance
• Multiple Inheritance
• Operator Overloading

Python Advanced Topics

• Python Iterator
• Python Generator
• Python Closure
• Python Decorators
• Python Property
• Python RegEx

Python Date and time

• Python datetime Module
• Python datetime.strftime()
• Python datetime.strptime()
• Current date & time
• Get current time
• Timestamp to datetime
• Python time Module
• Python time.sleep()

Python Tutorials

Python Dictionary clear()

Python Dictionary items()

• Python Dictionary keys()

Python Dictionary fromkeys()

• Python Nested Dictionary
• Python Dictionary update()

A Python dictionary is a collection of items, similar to lists and tuples. However, unlike lists and tuples, each item in a dictionary is a key-value pair (consisting of a key and a value).

• Create a Dictionary

We create a dictionary by placing key: value pairs inside curly brackets {} , separated by commas. For example,

• Dictionary keys must be immutable, such as tuples, strings, integers, etc. We cannot use mutable (changeable) objects such as lists as keys.
• We can also create a dictionary using a Python built-in function dict() . To learn more, visit Python dict() .

Valid and Invalid Dictionaries

Immutable objects can't be changed once created. Some immutable objects in Python are integer, tuple and string.

In this example, we have used integers, tuples, and strings as keys for the dictionaries. When we used a list as a key, an error message occurred due to the list's mutable nature.

Note: Dictionary values can be of any data type, including mutable types like lists.

The keys of a dictionary must be unique. If there are duplicate keys, the later value of the key overwrites the previous value.

Here, the key Harry Potter is first assigned to Gryffindor . However, there is a second entry where Harry Potter is assigned to Slytherin .

As duplicate keys are not allowed in a dictionary, the last entry Slytherin overwrites the previous value Gryffindor .

• Access Dictionary Items

We can access the value of a dictionary item by placing the key inside square brackets.

Note: We can also use the get() method to access dictionary items.

• Add Items to a Dictionary

We can add an item to a dictionary by assigning a value to a new key. For example,

• Remove Dictionary Items

We can use the del statement to remove an element from a dictionary. For example,

Note : We can also use the pop() method to remove an item from a dictionary.

If we need to remove all items from a dictionary at once, we can use the clear() method.

• Change Dictionary Items

Python dictionaries are mutable (changeable). We can change the value of a dictionary element by referring to its key. For example,

Note : We can also use the update() method to add or change dictionary items.

• Iterate Through a Dictionary

A dictionary is an ordered collection of items (starting from Python 3.7), therefore it maintains the order of its items.

We can iterate through dictionary keys one by one using a for loop .

• Find Dictionary Length

We can find the length of a dictionary by using the len() function.

• Python Dictionary Methods

Here are some of the commonly used dictionary methods .

• Dictionary Membership Test

We can check whether a key exists in a dictionary by using the in and not in operators.

Note: The in operator checks whether a key exists; it doesn't check whether a value exists or not.

Table of Contents

Video: python dictionaries to store key/value pairs.

Sorry about that.

Related Tutorials

Python Library

Python Tutorial

Python dict() — A Simple Guide with Video

Python’s built-in dict() function creates and returns a new dictionary object from the comma-separated argument list of key = value mappings. For example, dict(name = 'Alice', age = 22, profession = 'programmer') creates a dictionary with three mappings: {'name': 'Alice', 'age': 22, 'profession': 'programmer'} . A dictionary is an unordered and mutable data structure, so it can be changed after creation.

Read more about dictionaries in our full tutorial about Python Dictionaries .

Learn by example! Here are some examples of how to use the dict() built-in function :

You can pass an arbitrary number of those comma-separated key = value pairs into the dict() constructor.

Video dict()

Syntax dict()

You can use the dict() method with an arbitrary number of key=value arguments, comma-separated.

Interactive Shell Exercise: Understanding dict()

Consider the following interactive code:

Exercise : Guess the output before running the code.

Check out my new Python book Python One-Liners (Amazon Link).

If you like one-liners, you’ll LOVE the book. It’ll teach you everything there is to know about a single line of Python code. But it’s also an introduction to computer science , data science, machine learning, and algorithms. The universe in a single line of Python!

The book was released in 2020 with the world-class programming book publisher NoStarch Press (San Francisco).

Publisher Link : https://nostarch.com/pythononeliners

The dict() function has many different options to be called with different types of arguments. You’ll learn different ways to use the dict() function next.

How to Create an Empty Dictionary?

You can create an empty d i ctionary by using Python’s built-in dict() function without any argument. This returns an empty dictionary. As the dictionary is a mutable data structure, you can add more mappings later by using the d[key] = value syntax.

How to Create a Dictionary Using Only Keyword Arguments?

You can create a dictionary with initial key: value mappings by using a list of comma-separated arguments such as in dict(name = 'Alice', age = 22) to create the dictionary {'name': 'Alice', 'age': 22} . These are called keyword arguments because each argument value has its associated keyword.

How to Create a Dictionary Using an Iterable?

You can initialize your new dictionary by using an iterable as an input for the dict(iterable) function. Python expects that the iterable contains (key, value) pairs. An example iterable is a list of tuples or a list of lists. The first values of the inner collection types are the keys and the second values of the inner collection types are the values of the new dictionary.

Note that you can use inner tuples, inner lists, outer tuples or outer lists—as long as each inner collection contains exactly two values. If it contains more, Python raises an ValueError: dictionary update sequence element .

You can fix this ValueError by passing only two values in the inner collections. For example use a list of tuples with only two but not three tuple elements.

How to Create a Dictionary Using an Existing Mapping Object?

If you already have a mapping object such as a dictionary mapping keys to values, you can pass this object as an argument into the dict() function. Python will then create a new dictionary based on the existing key: value mappings in the argument. The resulting dictionary will be a new object so if you change it, the changes are not reflected in the original mapping object.

If you now change the original dictionary, the change is not reflected in the new dictionary d2 .

How to Create a Dictionary Using a Mapping Object and Keyword Arguments?

Interestingly, you can also pass a mapping object into the dict() function and add some more key: value mappings using keyword arguments after the first mapping argument. For example, dict({'Alice': 22}, Bob = 23) creates a new dictionary with both key:value mappings {'Alice': 22, 'Bob': 23} .

How to Create a Dictionary Using an Iterable and Keyword Arguments?

Similarly, you can also pass an iterable of (key, value) tuples into the dict() function and add some more key: value mappings using keyword arguments after the first mapping argument. For example, dict([('Alice', 22)], Bob = 23) creates a new dictionary with both key:value mappings {'Alice': 22, 'Bob': 23} .

Python’s built-in dict() function creates and returns a new dictionary object from the comma-separated argument list of key = value mappings.

For example, dict(name = 'Alice', age = 22, profession = 'programmer') creates a dictionary with three mappings: {'name': 'Alice', 'age': 22, 'profession': 'programmer'} .

A dictionary is an unordered and mutable data structure, so it can be changed after creation.

I hope you enjoyed the article! To improve your Python education, you may want to join the popular free Finxter Email Academy :

Do you want to boost your Python skills in a fun and easy-to-consume way? Consider the following resources and become a master coder!

Where to Go From Here?

Enough theory. Let’s get some practice!

Coders get paid six figures and more because they can solve problems more effectively using machine intelligence and automation.

To become more successful in coding, solve more real problems for real people. That’s how you polish the skills you really need in practice. After all, what’s the use of learning theory that nobody ever needs?

You build high-value coding skills by working on practical coding projects!

Do you want to stop learning with toy projects and focus on practical code projects that earn you money and solve real problems for people?

🚀 If your answer is YES! , consider becoming a Python freelance developer ! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.

If you just want to learn about the freelancing opportunity, feel free to watch my free webinar “How to Build Your High-Income Skill Python” and learn how I grew my coding business online and how you can, too—from the comfort of your own home.

Join the free webinar now!

While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.

To help students reach higher levels of Python success, he founded the programming education website Finxter.com that has taught exponential skills to millions of coders worldwide. He’s the author of the best-selling programming books Python One-Liners (NoStarch 2020), The Art of Clean Code (NoStarch 2022), and The Book of Dash (NoStarch 2022). Chris also coauthored the Coffee Break Python series of self-published books. He’s a computer science enthusiast, freelancer , and owner of one of the top 10 largest Python blogs worldwide.

His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.

Effortlessly Add Keys to Python Dictionaries: A Complete Guide

Dictionaries are a built-in data structure in Python used for mapping keys to values. They are similar to lists, but instead of using indices to access values, you use keys. In this article, we’ll explore how to add keys to dictionary in Python and how to use them effectively in your code.

Creating a Dictionary

The syntax for creating a dictionary in Python is straightforward. You enclose a comma-separated list of key-value pairs within curly braces:

Adding Keys to a Dictionary

There are several ways to add keys to a dictionary in Python. One common method is to use square brackets and assignment:

Another way to add keys to a dictionary in Python is to use the update() method:

Updating Existing Keys

If you add a key to a dictionary that already exists, the value associated with that key will be updated:

Using the get() Method

When you’re working with dictionaries, it’s important to be able to access the values associated with specific keys. One way to do this is to use square brackets:

However, this approach can cause an error if you try to access a key that doesn’t exist in the dictionary. To avoid this, you can use the get() method instead:

The get() method takes two arguments: the first is the key you want to access, and the second is an optional default value to return if the key doesn’t exist.

Add keys to a dictionary using for loop

You can add keys to a dictionary within a loop by using the dictionary’s bracket notation to access and add items. Here’s an example:

In this example, we first define an empty dictionary called my_dict . We also define a list of keys ( keys ) and a list of values ( values ). We then loop through the keys and values using a for loop that goes through the range of the length of the keys list.

Within the loop, we use the bracket notation to access the key at the current index of the keys list ( keys[i] ) and add the corresponding value from the values list ( values[i] ) as the value for that key in the dictionary ( my_dict[keys[i]] = values[i] ).

After the loop, we print the resulting dictionary, which should contain the key-value pairs from the keys and values lists.

Add keys to dictionary if not exists

To add keys to a dictionary only if they don’t already exist, you can use the setdefault() method of the dictionary. This method sets a key to a default value if the key is not already in the dictionary. Here’s an example:

In this example, we first define a dictionary called my_dict with some initial keys and values. We also define a list of keys ( keys ) and a list of values ( values ). We then loop through the keys and values using a for loop that goes through the range of the length of the keys list.

Within the loop, we use the setdefault() method to add the key-value pair to the dictionary only if the key doesn’t already exist in the dictionary. If the key already exists, the setdefault() method returns the current value for that key without changing it.

After the loop, we print the resulting dictionary, which should contain all the original keys and values from the dictionary, as well as any new key-value pairs that were added from the keys and values lists.

Add tuple as key to dictionary

You can use a tuple as a key for a dictionary in Python. Here’s an example:

we define a dictionary called my_dict with a tuple key ('a', 1) and a corresponding value 'apple' . We can access the value for this key using the bracket notation my_dict[('a', 1)] .

To add a new key-value pair with a tuple key, we can simply use the bracket notation to assign a value to a new tuple key ('b', 2) like so: my_dict[('b', 2)] = 'banana' .

Add key to dictionary using list comprehension

You can add keys to a dictionary using a list comprehension by creating a dictionary with the key-value pairs and then using dictionary comprehension to filter and add keys to the original dictionary. Here’s an example:

In this example, we define the original dictionary my_dict , and a list of keys to add keys_to_add , and a value for the new keys value .

We create a new dictionary new_dict with the key-value pairs to add, using a dictionary comprehension to create a dictionary with keys from the keys_to_add list, and a value of value .

We then use the ** operator to unpack both dictionaries ( my_dict and new_dict ) into a new dictionary. This is done in a dictionary comprehension to add the new keys to the original dictionary and any existing keys in my_dict will be overwritten with the new value of value .

Finally, we print the updated dictionary with the new keys added.

Yes, you can add a key with multiple values to a dictionary by assigning a list or another dictionary as the value.

Yes, you can add a key with a value of any data type to a dictionary, including strings, integers, floating-point numbers, lists, dictionaries, and more.

Dictionaries are a powerful tool for mapping keys to values in Python. By adding keys to dictionaries, you can store and retrieve information in a flexible and efficient way. Whether you’re using square brackets and assignment, the update() method, or the get() method, there are many ways to work with dictionaries in Python.

It’s important to keep in mind that dictionaries are unordered, which means that the keys and values may not be stored in the order you expect. However, you can use the sorted() function to sort the keys in a dictionary, or you can use the collections module to create an ordered dictionary that preserves the order of the keys.

Whether you’re a beginner or an experienced programmer, understanding dictionaries and how to add keys to them is a valuable skill to have. Try incorporating dictionaries into your own projects, and see how they can simplify your code and improve your workflow.

Trending Python Articles

• Free Python 3 Tutorial
• Control Flow
• Exception Handling
• Python Programs
• Python Projects
• Python Interview Questions
• Python Database
• Data Science With Python
• Machine Learning with Python
• How to create a Dictionary in Python
• Get length of dictionary in Python
• Python - Value length dictionary
• Python - Dictionary values String Length Summation
• Python - Dictionary value lists lengths product
• Access Dictionary Values | Python Tutorial
• Python - Dictionary items in value range
• Python | Ways to change keys in dictionary
• Python Program to Swap dictionary item's position
• Python | Merging two Dictionaries
• How to Compare Two Dictionaries in Python?
• Python Dictionary Comprehension
• How to add values to dictionary in Python

Python | Add new keys to a dictionary

• Python - Add item after given Key in dictionary
• Python | Ways to remove a key from dictionary
• Python | Removing dictionary from list of dictionaries
• Python | Remove item from dictionary when key is unknown
• Python - Test if all Values are Same in Dictionary
• Python | Test if element is dictionary value
• Why is iterating over a dictionary slow in Python?
• Iterate over a dictionary in Python
• Python - How to Iterate over nested dictionary ?
• Python | Delete items from dictionary while iterating
• Python Dictionary Methods

Before learning how to add items to a dictionary, let’s understand in brief what a  dictionary is. A Dictionary in Python is an unordered collection of data values, used to store data values like a map, unlike other data types that hold only a single value as an element, a Dictionary holds a key: value pair. 

Key-value is provided in the dictionary to make it more optimized. A colon separates each key-value pair in a Dictionary: whereas each key is separated by a ‘comma’. 

The keys of a Dictionary must be unique and of immutable data types such as Strings, Integers, and tuples, but the key values can be repeated and be of any type. In this article, we will cover how to add to a Dictionary in Python .

How to Add Keys and Values to a Dictionary

To add a new item in the dictionary, you need to add a new key and insert a new value respective to it. There are various methods to add items to a dictionary in Python here we explain some generally used methods to add to a dictionary in Python. 

• Using Subscript notation 
• Using update() Method
• Using __setitem__ Method
• Using the  ** operator 
• Using If statements
• Using enumerate() Method
• Using a Custom Class
• Using Merge | Operator

Add to a Python Dictionary using the Subscript Notation

This method will create a new key/value pair on a dictionary by assigning a value to that key. If the key doesn’t exist, it will be added and point to that value. If the key exists, its current value will be overwritten. 

Add to a Python Dictionary using update() Method

When we have to update/add a lot of keys/values to the dictionary, the update() method is suitable. The update() method inserts the specified items into the dictionary.

Add to Python Dictionary using the __setitem__ Method

The __setitem__ method is used to add a key-value pair to a dictionary. It should be avoided because of its poor performance (computationally inefficient).

Add to Python Dictionary using the ** Operator

We can merge the old dictionary and the new key/value pair in another dictionary. Using ** in front of key-value pairs like  **{‘c’: 3} will unpack it as a new dictionary object.

Add to Python Dictionary using the “in” operator and IF statements

If the key is not already present in the dictionary, the key will be added to the dictionary using the if statement . If it is evaluated to be false, the “ Dictionary already has a key ” message will be printed.

Add to Python Dictionary using enumerate() Method

Use the enumerate() method to iterate the list, and then add each item to the dictionary by using its index as a key for each value.

Add Multiple Items to a Python Dictionary with Zip

In this example, we are using a zip method of Python for adding keys and values to an empty dictionary python . You can also use an in the existing dictionary to add elements in the dictionary in place of a dictionary = {}.

Add New Keys to Python Dictionary with a Custom Class

At first, we have to learn how we create dictionaries in Python. It defines a class called my_dictionary that inherits from the built-in dict class. The class has an __init__ method that initializes an empty dictionary, and a custom add method that adds key-value pairs to the dictionary.

Add New Keys to a Dictionary using the Merge | Operator

In this example, the below Python code adds new key-value pairs to an existing dictionary using the `|=` merge operator. The `my_dict` dictionary is updated to include the new keys and values from the `new_data` dictionary.

In this tutorial, we have covered multiple ways to add items to a Python dictionary. We have discussed easy ways like the update() method and complex ways like creating your own class. Depending on whether you are a beginner or an advanced programmer, you can choose from a wide variety of techniques to add to a dictionary in Python. 

You can read more informative articles on how to add to a dictionary:

• Append Dictionary Keys and Values in Python
• Add a key:value pair to dictionary in Python
• Add item after given Key in dictionary

Please Login to comment...

Similar reads.

• Python dictionary-programs
• python-dict
• How to Use ChatGPT with Bing for Free?
• 7 Best Movavi Video Editor Alternatives in 2024
• How to Edit Comment on Instagram
• 10 Best AI Grammar Checkers and Rewording Tools
• 30 OOPs Interview Questions and Answers (2024)

Improve your Coding Skills with Practice

What kind of Experience do you want to share?