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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

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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.

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Python Dictionary Modification

A dictionary in Python is an unordered collection of key-value pairs. It is a mutable data type, which means that we can modify its contents by adding, changing, or removing elements

To add a new key-value pair to a dictionary, we can use the assignment operator =. For example:

We can also add multiple key-value pairs at once using the update() method:

Change Items

To change the value associated with a particular key in a dictionary, we can simply reassign the value using the assignment operator =. For example:

Remove Items

There are several ways to remove elements from a dictionary in Python.

Using the del Statement

We can use the del statement to remove a specific key-value pair from a dictionary:

Using the pop() Method

We can use the pop() method to remove a specific key-value pair from a dictionary and return its value:

Using the popitem() Method

We can use the popitem() method to remove and return a randomly chosen key-value pair from a dictionary:

Combine Dictionaries

There are several ways to combine (or merge) dictionaries in Python.

Using the update() Method

We can use the update() method to add the key-value pairs from one dictionary to another:

Best Practices

When adding multiple key-value pairs to a dictionary at once, consider using the update() method instead of repeatedly using the assignment operator =. This is more efficient and easier to read.

When changing the value associated with a particular key in a dictionary, be sure to use the correct key. A KeyError exception will be raised if the key does not exist in the dictionary.

When using the del statement or the pop() method to remove a key-value pair from a dictionary, be sure to use the correct key. A KeyError exception will be raised if the key does not exist in the dictionary.

Consider using the pop() method instead of the del statement if you need to store the value of the removed key-value pair.

When combining dictionaries, consider the order in which the key-value pairs are added. If a key exists in both dictionaries, the value from the second dictionary will overwrite the value from the first dictionary.

Consider using the update() method or the {**dict1, **dict2} syntax to create a new dictionary that contains all of the key-value pairs from both dictionaries. This is more efficient and easier to read than using a loop to manually add the key-value pairs.

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A Python dictionary is a collection of items that allows us to store data in key: value pairs.

  • Create a Dictionary

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

Key Value Pairs in a Dictionary

  • 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.

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Python Create Dictionary – The Ultimate Guide

Introduction to python dictionaries.

A Python dictionary is a built-in data structure that allows you to store data in the form of key-value pairs. It offers an efficient way to organize and access your data.

In Python, creating a dictionary is easy. You can use the dict() function or simply use curly braces {} to define an empty dictionary.

For example:

This will create an empty dictionary called my_dictionary . To add data to the dictionary, you can use the following syntax:

In this case, "key1" and "key2" are the keys, while "value1" and "value2" are the corresponding values. Remember that the keys must be unique, as duplicate keys are not allowed in Python dictionaries .

One of the reasons why dictionaries are important in programming projects is their efficient access and manipulation of data. When you need to retrieve a value, simply provide the corresponding key:

This will return the value associated with "key1" , in this case, "value1" . If the key does not exist in the dictionary, Python will raise a KeyError .

Dictionaries also support various methods for managing the data, such as updating the values, deleting keys, or iterating through the key-value pairs.

Basic Dictionary Creation

In this section, we will discuss the basic methods of creating dictionaries.

To create an empty dictionary, you can use a pair of curly braces, {} . This will initialize an empty dictionary with no elements. For example:

Another method to create an empty dictionary is using the dict() function:

Once you have an empty dictionary, you can start populating it with key-value pairs. To add elements to your dictionary, use the assignment operator = and square brackets [] around the key:

Alternatively, you can define key-value pairs directly in the dictionary using the curly braces {} method. In this case, each key is separated from its corresponding value by a colon : , and the key-value pairs are separated by commas , :

The dict() function can also be used to create a dictionary by passing a list of tuples , where each tuple is a key-value pair:

Creating Dictionaries from Lists and Arrays

Python create dict from list.

To create a dictionary from a list, first make sure that the list contains mutable pairs of keys and values. One way to achieve this is by using the zip() function. The zip() function allows you to combine two lists into a single list of pairs.

Next, use the dict() function to convert the combined list into a dictionary:

Python Create Dict From Two Lists

To create a dictionary from two separate lists, you can utilize the zip() function along with a dictionary comprehension. This method allows you to easily iterate through the lists and create key-value pairs simultaneously:

The How to Create a Dictionary from two Lists post provides a detailed explanation of this process.

Python Create Dict From List Comprehension

List comprehension is a powerful feature in Python that allows you to create a new list by applying an expression to each element in an existing list or other iterable data types. You can also use list comprehension to create a dictionary:

Python Create Dict From List in One Line

To create a dictionary from a list in just one line of code, you can use the zip() function and the dict() function:

Python Dictionary Comprehension - A Powerful One-Liner Tutorial

πŸ’‘ Recommended : Python Dictionary Comprehension: A Powerful One-Liner Tutorial

Python Create Dict From a List of Tuples

If you have a list of tuples, where each tuple represents a key-value pair, you can create a dictionary using the dict() function directly:

Python Create Dict From Array

To create a dictionary from an array or any sequence data type, first convert it into a list of tuples, where each tuple represents a key-value pair. Then, use the dict() function to create the dictionary:

Note that the values in this example are strings because the NumPy array stores them as a single data type. You can later convert these strings back to integers if needed.

Creating Dictionaries from Strings and Enumerations

Python create dict from string.

To create a dictionary from a string, you can use a combination of string manipulation and dictionary comprehension . This method allows you to extract key-value pairs from the given string, and subsequently populate the dictionary.

The following example demonstrates how to create a dictionary from a string:

In this example, the input string is split into a list of smaller strings using , as the separator. Then, a dictionary comprehension is used to split each pair by the = sign, creating the key-value pairs.

Python Create Dict from Enumerate

The enumerate() function can also be used to create a dictionary. This function allows you to create key-value pairs, where the key is the index of a list item, and the value is the item itself.

Here is an example of using enumerate() to create a dictionary:

In this example, the enumerate() function is used in a dictionary comprehension to create key-value pairs with the index as the key and the list item as the value.

Python Create Dict From Enum

Python includes an Enum class, which can be used to create enumerations. Enumerations are a way to define named constants that have a specific set of values. To create a dictionary from an enumeration, you can loop through the enumeration and build key-value pairs.

Here’s an example of creating a dictionary from an enumeration:

In this example, an enumeration called Color is defined and then used in a dictionary comprehension to create key-value pairs with the color name as the key and the color value as the value.

When working with dictionaries in Python, it’s essential to be aware of potential KeyError exceptions that can occur when trying to access an undefined key in a dictionary. This can be handled using the dict.get() method, which returns a specified default value if the requested key is not found.

Also, updating the dictionary’s key-value pairs is a simple process using the assignment operator, which allows you to either add a new entry to the dictionary or update the value for an existing key.

Creating Dictionaries from Other Dictionaries

In this section, you’ll learn how to create new dictionaries from existing ones. We’ll cover how to create a single dictionary from another one, create one from two separate dictionaries, create one from multiple dictionaries, and finally, create one from a nested dictionary.

Python Create Dict From Another Dict

To create a new dictionary from an existing one, you can use a dictionary comprehension. The following code snippet creates a new dictionary with keys and values from the old one, in the same order.

If you want to modify the keys or values in the new dictionary, simply apply the modifications within the comprehension:

Python Create Dict From Two Dicts

Suppose you want to combine two dictionaries into one. You can do this using the update() method or union operator | . The update() method can add or modify the keys from the second dictionary in the first one.

Here’s an example:

If you’re using Python 3.9 or later, you can utilize the union operator | to combine two dictionaries:

Keep in mind that in case of overlapping keys, the values from the second dictionary will take precedence.

πŸ’« Master Tip: Python Create Dict From Multiple Dicts

If you want to combine multiple dictionaries into one, you can use the ** unpacking operator in a new dictionary:

The combined_dict will contain all the keys and values from dict1 , dict2 , and dict3 . In case of overlapping keys, the values from later dictionaries will replace those from the earlier ones.

Python Create Dict From Nested Dict

When working with a nested dictionary , you might want to create a new dictionary from a sub-dictionary. To do this, use the key to access the nested dictionary, and then make a new dictionary from the sub-dictionary:

In the code above, the new_dict will be created from the sub-dictionary with the key 'a' .

Creating Dictionaries from Files and Data Formats

In this section, we will explore ways to create Python dictionaries from various file formats and data structures. We will cover the following topics:

Python Create Dict From CSV

Creating a dictionary from a CSV file can be achieved using Python’s built-in csv module. First, open the CSV file with a with statement and then use csv.DictReader to iterate over the rows, creating a dictionary object for each row:

Python Create Dict From Dataframe

When working with Pandas DataFrames, you can generate a dictionary from the underlying data using the to_dict() method:

This will create a dictionary where the DataFrame index is set as keys and the remaining data as values.

Python Create Dict From Dataframe Columns

To create a dictionary from specific DataFrame columns, use the zip function and the to_dict() method:

Python Create Dict From Excel

Openpyxl is a Python library that helps you work with Excel ( .xlsx ) files. Use it to read the file, iterate through the rows, and add the data to a dictionary:

Python Create Dict From YAML File

To create a dictionary from a YAML file, you can use the PyYAML library. Install it using pip install PyYAML . Then read the YAML file and convert it into a dictionary object:

Python Create Dict From Json File

To generate a dictionary from a JSON file, use Python’s built-in json module to read the file and decode the JSON data:

Python Create Dict From Text File

To create a dictionary from a text file, you can read its contents and use some custom logic to parse the keys and values:

Modify the parsing logic according to the format of your input text file. This will ensure you correctly store the data as keys and values in your dictionary.

Advanced Dictionary Creation Methods

Python create dict from variables.

You can create a dictionary from variables using the dict() function. This helps when you have separate variables for keys and values. For example:

Python Create Dict From Arguments

Another way to create dictionaries is by using the **kwargs feature in Python. This allows you to pass keyword arguments to a function and create a dictionary from them. For example:

Python Create Dict From Iterator

You can also create a dictionary by iterating over a list and using list comprehensions, along with the get() method. This is useful if you need to count occurrences of certain elements:

Python Create Dict From User Input

To create a dictionary from user input, you can use a for loop. Prompt users to provide input and create the dictionary with the key-value pairs they provide:

Python Create Dict From Object

You can create a dictionary from an object’s attributes using the built-in vars() function. This is helpful when converting an object to a dictionary. For example:

Python Create Dict Zip

Lastly, you can create a dictionary using the zip() function and the dict() constructor. This is useful when you have two lists β€” one representing keys and the other representing values:

Frequently Asked Questions

How do you create an empty dictionary in python.

To create an empty dictionary in Python, you can use either a set of curly braces {} or the built-in dict() function. Here are examples of both methods:

What are common ways to create a dictionary from two lists?

To create a dictionary from two lists, you can use the zip function in combination with the dict() constructor. Here’s an example:

In this example, my_dict will be {'a': 1, 'b': 2, 'c': 3} .

What are the key dictionary methods in Python?

Some common dictionary methods in Python include:

  • get(key, default) : Returns the value associated with the key if it exists; otherwise, returns the default value.
  • update(other) : Merges the current dictionary with another dictionary or other key-value pairs.
  • keys() : Returns a view object displaying all the keys in the dictionary.
  • values() : Returns a view object displaying all the values in the dictionary.
  • items() : Returns a view object displaying all the key-value pairs in the dictionary.

How do I create a dictionary if it does not exist?

You can use a conditional statement along with the globals() function to create a dictionary if it does not exist. Here’s an example:

In this case, my_dict will only be created if it does not already exist in the global namespace.

How can I loop through a dictionary in Python?

You can loop through a dictionary in Python using the items() method, which returns key-value pairs. Here’s an example:

This code will output:

What is an example of a dictionary in Python?

A dictionary in Python is a collection of key-value pairs enclosed in curly braces. Here’s an example:

In this example, the keys are fruit names, and the values are quantities.

πŸ’‘ Recommended : Python Dictionary – The Ultimate Guide

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  • 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 β€œin” 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

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Assign a dictionary Key or Value to variable in Python

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Last updated: Feb 21, 2023 Reading time Β· 4 min

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# Table of Contents

  • Assign a dictionary value to a Variable in Python
  • Assign dictionary key-value pairs to variables in Python
  • Assign dictionary key-value pairs to variables using exec()

# Assign a dictionary value to a Variable in Python

Use bracket notation to assign a dictionary value to a variable, e.g. first = my_dict['first_name'] .

The left-hand side of the assignment is the variable's name and the right-hand side is the value.

assign dictionary value to variable

The first example uses square brackets to access a dictionary key and assigns the corresponding value to a variable.

If you need to access the dictionary value using an index , use the dict.values() method.

The dict.values method returns a new view of the dictionary's values.

We had to use the list() class to convert the view object to a list because view objects are not subscriptable (cannot be accessed at an index).

You can use the same approach if you have the key stored in a variable.

If you try to access a dictionary key that doesn't exist using square brackets, you'd get a KeyError .

On the other hand, the dict.get() method returns None for non-existent keys by default.

The dict.get method returns the value for the given key if the key is in the dictionary, otherwise a default value is returned.

The method takes the following 2 parameters:

If a value for the default parameter is not provided, it defaults to None , so the get() method never raises a KeyError .

If you need to assign the key-value pairs of a dictionary to variables, update the locals() dictionary.

# Assign dictionary key-value pairs to variables in Python

Update the locals() dictionary to assign the key-value pairs of a dictionary to variables.

assign dictionary key value pairs to variables

The first example uses the locals() dictionary to assign the key-value pairs of a dictionary to local variables.

The locals() function returns a dictionary that contains the current scope's local variables.

The dict.update method updates the dictionary with the key-value pairs from the provided value.

You can access the variables directly after calling the dict.update() method.

The SimpleNamespace class can be initialized with keyword arguments.

The keys of the dictionary are accessible as attributes on the namespace object.

Alternatively, you can use the exec() function.

# Assign dictionary key-value pairs to variables using exec()

This is a three-step process:

  • Iterate over the dictionary's items.
  • Use the exec() function to assign each key-value pair to a variable.
  • The exec() function supports dynamic execution of Python code.

assign dictionary key value pairs to variables using exec

The dict.items method returns a new view of the dictionary's items ((key, value) pairs).

On each iteration, we use the exec() function to assign the current key-value pair to a variable.

The exec function supports dynamic execution of Python code.

The function takes a string, parses it as a suite of Python statements and runs the code.

Which approach you pick is a matter of personal preference. I'd go with the SimpleNamespace class to avoid any linting errors for trying to access undefined variables.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

  • Check if all values in a Dictionary are equal in Python
  • How to Replace values in a Dictionary in Python
  • Get multiple values from a Dictionary in Python
  • Get random Key and Value from a Dictionary in Python
  • Join the Keys or Values of Dictionary into String in Python
  • Multiply the Values in a Dictionary in Python
  • Print specific key-value pairs of a dictionary in Python
  • How to set all Dictionary values to 0 in Python
  • Sum all values in a Dictionary or List of Dicts in Python
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COMMENTS

  1. Answer in Python for Ram #296889

    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. Input

  2. Answer in Python for sai krishna #288912

    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 Word

  3. Create a 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, {}. #create an empty dictionary my_dictionary = {} print(my_dictionary) #to check the data type use the type () function print(type(my_dictionary)) #output # {} #<class 'dict'>

  4. Dictionaries in Python

    Here's what you'll learn in this tutorial: You'll cover the basic characteristics of Python dictionaries and learn how to access and manage dictionary data. Once you have finished this tutorial, you should have a good sense of when a dictionary is the appropriate data type to use, and how to do so.

  5. 12 Examples to Master Python Dictionaries

    5. Updating with a new dictionary. We can also pass a dictionary to the update function. The dictionary will be updated based on the items in the new dictionary. It will become more clear with an examples. Consider the following grades and grades_new dictionaries:

  6. Python Dictionary Modification (with Best Practices)

    This tutorial includes code examples and best practices to help you master dictionary modification in Python. Skip to content ... To add a new key-value pair to a dictionary, we can use the assignment operator =. ... **dict2} Syntax We can use the {**dict1, **dict2} syntax to merge two dictionaries into a new dictionary: ```python # Initialize ...

  7. Python Dictionary (With Examples)

    A Python dictionary is a collection of items that allows us to store data in key: value pairs. Create a Dictionary We create a dictionary by placing key: value pairs inside curly brackets {}, separated by commas. For example,

  8. Python Create Dictionary

    Introduction to Python Dictionaries. A Python dictionary is a built-in data structure that allows you to store data in the form of key-value pairs. It offers an efficient way to organize and access your data. In Python, creating a dictionary is easy. You can use the dict() function or simply use curly braces {} to define an empty dictionary.. For example:

  9. Creating a new dictionary in Python

    8 Answers Sorted by: 762 Call dict with no parameters new_dict = dict() or simply write new_dict = {} Share Improve this answer Follow edited Nov 8, 2015 at 3:49 poolie 9,319 1 48 74 answered Dec 8, 2011 at 1:13 Jan Vorcak 19.5k 15 54 90 50 Is there any difference between dict () and {}?

  10. How to create a Dictionary in Python

    In Python, a dictionary can be created by placing a sequence of elements within curly {} braces, separated by a 'comma'. Let us see a few examples to see how we can create a dictionary in Python. Define a Dictionary with Items

  11. Python

    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. Python3 dict = {'key1': 'geeks', 'key2': 'fill_me'} print("Current Dict is:", dict) dict['key2'] = 'for' dict['key3'] = 'geeks'

  12. Assign a dictionary Key or Value to variable in Python

    # Assign a dictionary value to a Variable in Python Use bracket notation to assign a dictionary value to a variable, e.g. first = my_dict['first_name'] . The left-hand side of the assignment is the variable's name and the right-hand side is the value.

  13. Python Dictionary Exercise with Solution [10 Exercise Questions]

    Exercise 1: Convert two lists into a dictionary Exercise 2: Merge two Python dictionaries into one Exercise 3: Print the value of key 'history' from the below dict Exercise 4: Initialize dictionary with default values Exercise 5: Create a dictionary by extracting the keys from a given dictionary Exercise 6: Delete a list of keys from a dictionary

  14. How do I assign a dictionary value to a variable in Python?

    There are various mistakes in your code. First you forgot the = in the first line. Additionally in a dict definition you have to use : to separate the keys from the values.. Next thing is that you have to define new_variable first before you can add something to it.. This will work:

  15. python

    2 Answers Sorted by: 17 You need to store a new dictionary inside of Data to make this work: Data [day1] = {} Data [day1] [e1] = 4 but normally you'd first test to see if that dictionary is there yet; using dict.setdefault () to make that a one-step process: if day1 not in Data Data [day1] = {} Data [day1] [e1] = 4

  16. Question about dictionary assignment in python

    1. id is not the identity function in Python. id (rec) returns the memory address of rec in CPython. This does not depend on the value or lifetime of rec. Similarly, releasing rec (via del) allows something else to be stored at that address. Whether this happens or not is an implementation detail of the memory management.