assign key to value python

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How can I assign a value of a existing key in a dictionary?

I have to check if a key is in the dictionary or not. if it is there I have to assign at the variable the value of the key otherwise create a new key with a value for a raw_input. I write the code below but it doesn't work. I have to check if the key is in the dictionary or not.

For example I have a database of food recipe. "Oil" is almost in all recipes so i can't insert a raw_input for all a row of database. So I want to create a dictionary and select the value there.

For example in the database i have 100 row with ingredient "oil". I match this database with another. The key is the name of ingredient (in this case "oil") and the value is the characteristic (corn oil). Each row with the key "oil" must have the value "corn oil". Can i make this using a dictionary?

Can you help me, please? Thank you very much.

• Currently your code just inserts value into the dict regardless of whether the key exists or not. What is your issue? What do you expect to happen and what is actually happening? Please, clarify. –  Назар Топольський Nov 9, 2016 at 9:53
• You're doing the same thing in the if and the else, what do you expect to happen ? –  polku Nov 9, 2016 at 9:53
• I have to check if the key is in the dictionary or not. If the key is in the dictionary i have to assing the same value at the new variable otherwise i have to key a couple {key: value}. For example i have a database of food recipe. Salt is almost in all so i can't insert a raw_input for all a row of database. I want to create a dictionary and select the value there. –  kyle1009 Nov 9, 2016 at 9:56
• 1 Indeed, both if branches do same thing. To check if key item is present in dict_ write if item in dict_: . Also, don't redefine built-in names: dict is type name. –  George Sovetov Nov 9, 2016 at 9:59
• 2 It would be great if you can give the example with the sample list and the dict that you want as final result. Because what you are asking is unclear to me –  Moinuddin Quadri Nov 9, 2016 at 10:06

7 Answers 7

In my opinion, you always do dict[item] = value for any case, both if exists the item at the dictionary or not, then you have to create a new variable, for the dictionary, but I don't know that method you want to use, or what it will be the new key if the key already exists.

Sorry for my poor english if you don't understand something, write it!

Item assignment will in both cases replace any existing value with the new one; there is no need to check if the key already exists.

I think this would help. You assign a new value if key is not present, else don't since the key already exist

• If the key exists, i have to assing the value to the new variable. For example in the database i have 100 row with ingredient "oil". I match this database with another. The key is the name of ingredient (in this case "oil") and the value is the characteristic (corn oil). Each row with the key "oil" must have the value "corn oil". Can i make this using a dictionary? –  kyle1009 Nov 9, 2016 at 10:12
• This is what I understood. Correct me if I am wrong. You have two tables where one table has ingredients in each single row and the other has columns such as | oil | corn oil | , if you find palm oil in the ingredients, you want to store it as | oil | palm oil| in that table, right? –  Vaulstein Nov 9, 2016 at 10:23

One way of doing it:

If item is not present in dictionary's keys, just create one with None as starting value. Then, assign value to key (now You're sure it is there).

execute this it will return what you want..

output for this :

How about this,

check if item in dict else input()

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Python: How to Add Keys to a Dictionary

• Introduction

A dictionary in Python is a collection of items that store data as key-value pairs. We can access and manipulate dictionary items based on their key. Dictionaries are mutable and allow us to add new items to them.

The quickest way to add a single item to a dictionary is by using a dictionary's index with a new key and assigning a value. For example, we add a new key-value pair like this:

Python allows adding multiple items to dictionaries as well. In this tutorial, we'll take a look at how to add keys to a dictionary in Python .

• Add Key to a Python Dictionary

There are multiple ways to add a new key-value pair to an existing dictionary. Let's have a look at a few common ways to do so.

• Add Key with Value

We can add a new key to a dictionary by assigning a value to it. If the key is already present, it overwrites the value it points to. The key has to be written in subscript notation to the dictionary like this:

This key-value pair will be added to the dictionary. If you're using Python 3.6 or later, it will be added as the last item of the dictionary.

Let's make a dictionary, and then add a new key-value pair with this approach:

This will result in:

• Add Key to Dictionary without Value

If you'd just like to add a key, without a value, you can simply put None instead of the value, with any of the methods covered in this article:

This results in:

• Add Multiple Key-Value Pairs with update()

In Python, we can add multiple key-value pairs to an existing dictionary. This is achieved by using the update() method. This method takes an argument of type dict or any iterable that has the length of two - like ((key1, value1),) , and updates the dictionary with new key-value pairs.

If the key is already present in the dictionary, it gets overwritten with the new value.

The keys can also be passed as keyword arguments to this method with their corresponding values, like dictionary.update(new_key=new_value) .

Note: This is arguably the most popular method of adding new keys and values to a dictionary.

Let's use the update() method to add multiple key-value pairs to a dictionary:

Running this code will produce the following output:

• Using Merge Operator (Python 3.9+)

From Python version 3.9, Merge ( | ) and Update ( |= ) operators have been added to the built-in dict class.

These are very convenient methods to add multiple key-value pairs to a dictionary. The Merge ( | ) operator creates a new dictionary with the keys and values of both of the given dictionaries. We can then assign this result to a new dictionary.

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Whereas the Update ( |= ) operator, adds the key-value pairs of the second dictionary into the first dictionary. So, the existing dictionary gets updated with multiple key-value pairs from another dictionary.

Here's an example of using Merge ( | ) and Update ( |= ) operators to add new keys to a dictionary:

This code will produce the following output on the Python(3.9+) interpreter:

In this tutorial, we learned how we can add a new key to a dictionary. We first added the key-value pair using subscript notation - we added a key to a dictionary by assigning a value to it. We then looked at the update() method to add multiple key-value pairs to a dictionary. We've also used the update() method with parameters of type dictionary, tuple, and keyword arguments. Lastly, we probed into the Merge and Update operators available from Python versions 3.9 onwards.

The update() method of dictionary proves to be the most popular way to add new keys to an existing dictionary.

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Python – Assign values to initialized dictionary keys

Sometimes, while working with python dictionaries, we can have a problem in which we need to initialize dictionary keys with values. We save a mesh of keys to be initialized. This usually happens during web development while working with JSON data. Lets discuss certain ways in which this task can be performed. 

Method #1 : Using dict() + zip() The combination of above methods can be used to perform this task. In this, we allot the list values to already constructed mesh and zip() helps in mapping values as per list index. 

Time Complexity: O(n), where n is the number of elements in the dictionary. Auxiliary Space: O(n), as we are using a dictionary and a list to store the values.

Method #2 : Using loop + zip() This is extended way in which this task can be performed. In this, we iterate through the zipped list and assign value to dictionary. 

Time Complexity: O(n) Auxiliary Space: O(n)

Method #3: Using keys() and for loop

Time Complexity: O(n), where n is the length of the list test_dict Auxiliary Space: O(n) additional space of size n is created where n is the number of elements in the res list

Method #4: Using dictionary comprehension

Use dictionary comprehension to create a new dictionary where the keys are the same as the original dictionary and the values are taken from the test_list. The enumerate() function is used to get the index of each key in the original dictionary, which is used to get the corresponding value from the test_list.

• Initialize a dictionary with some keys and empty values.
• Create a list of values that need to be assigned to the keys of the dictionary.
• Print the original dictionary to verify the initial state.
• Use any of the provided methods (or the new method) to assign the values to the keys of the dictionary.
• Print the updated dictionary to verify the assigned values.

Time complexity: O(n), where n is the number of keys in the dictionary Auxiliary space: O(n), where n is the number of keys in the dictionary

Method #5: Using dictionary.update() method

• Initialize the dictionary test_dict with 3 keys and empty values.
• Initialize the list test_list with 3 elements.
• Print the original dictionary test_dict.
• Loop through the keys in test_dict using enumerate() to get the index i and the key itself key.
• Update the value of the key in test_dict using update() method with a new dictionary containing only the key-value pair key: test_list[i].
• Print the resulting dictionary test_dict with assigned values.

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Add a key value pair to dictionary in Python

Python dictionaries are an unordered collection of key value pairs. In this tutorial we will see how we can add new key value pairs to an already defined dictionary. Below are the two approaches which we can use.

Assigning a new key as subscript

We add a new element to the dictionary by using a new key as a subscript and assigning it a value.

Running the above code gives us the following result −

Using the update() method

The update() method directly takes a key-value pair and puts it into the existing dictionary. The key value pair is the argument to the update function. We can also supply multiple key values as shown below.

By merging two dictionaries

We can also append elements to a dictionary by merging two dictionaries. Here again, we use the update() method but the argument to the method is a dictionary itself.

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Python dictionary append: How to Add Key/Value Pair?

• Dictionary in Python
• Restrictions on Key Dictionaries
• Creating a Dictionary
• Dictionary with integer keys
• Accessing elements of a dictionary
• Deleting element(s) in a dictionary
• Deleting Element(s) from dictionary using pop() method
• Appending element(s) to a dictionary
• Updating existing element(s) in a dictionary
• Insert a dictionary into another dictionary
• Quick Programs on Python Dictionary Append

Python is a popular programming language that offers a wide range of built-in data structures, including lists, tuples, sets, and dictionaries. Among these, dictionaries are one of the most commonly used data structures in Python due to their ability to store data in a key-value pair format.

Python dictionaries are a powerful data structure that allows you to store and manipulate data in a key-value pair format. One common task when working with dictionaries is to append new values to an existing dictionary. While Python dictionaries do not have an append() method like lists do, there are several ways to add new key-value pairs to a dictionary. In this blog post, we will explore some of these methods and discuss when to use each one. So, let’s dive in!

A dictionary is an important data type in Python programming. It is a collection of data values that are unordered. Python dictionary is used to store items in which each item has a key-value pair. The dictionary is made up of these key-value pairs, and this makes the dictionary more optimized. 

For example –

Here, 

The colon is used to pair keys with the values.

The comma is used as a separator for the elements. 

The output is:

{1: ‘Learnings’, 2: ‘For’, 3: ‘Life’}

Python dictionary append is simply used to add key/value to the existing dictionary. The dictionary objects are mutable. Unlike other objects, the dictionary simply stores a key along with its value. Therefore, the combination of a key and its subsequent value represents a single element in the Python dictionary.  

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Below are enlisted some restrictions on the key dictionaries –

• A given key appears only once in a dictionary. Duplicates of keys are not allowed. 
• It won’t make sense if you map a particular key more than once. This is so because the dictionary will map each key to its value.
• In case of a duplication of a key, the last one will be considered.
• If a key is specified a second time after the creation of a dictionary, then the second time will be considered as it will override the first time.
• The key must be immutable, which means that the data type can be an integer, string, tuple, boolean, etc. Therefore, lists or another dictionary can not be used as they are changeable.  

How to append an element to a key in a dictionary with Python?

In Python, you can create a dictionary easily using fixed keys and values. The sequence of elements is placed within curly brackets, and key: values are separated by commas. It must be noted that the value of keys can be repeated but can not have duplicates. Also, keys should have immutable data types such as strings, tuples, or numbers. 

Here’s an example –

The output is :

Dictionary with the use of Integer Keys: 

{1: ‘Learning’, 2: ‘For’, 3: ‘Life’}

Dictionary with the use of Mixed Keys: 

{‘Name’: ‘GreatLearning’, 1: [1, 2, 3, 4]}

Here’s how to create a dictionary using the integer keys –

Dictionary ‘dict_a’ is…

{1: ‘India’, 2: ‘USA’, 3: ‘UK’, 4: ‘Canada’}

Dictionary ‘dict_a’ keys…

Dictionary ‘dict_a’ values…

Dictionary ‘dict_a’ keys & values…

Key names are used to access elements of a dictionary. To access the elements, you need to use square brackets ([‘key’]) with the key inside it. 

Accessing an element using key:

Alternative method 

There’s another method called get() that is used to access elements from a dictionary. In this method, the key is accepted as an argument and returned with a value. 

Accessing an element using get:

You can delete elements in a dictionary using the ‘del’ keyword.

The syntax is –

Use the following syntax to delete the entire dictionary –

Another alternative is to use the clear() method. This method helps to clean the content inside the dictionary and empty it. The syntax is –

Let us check an example of the deletion of elements that result in emptying the entire dictionary –

{’email’: ‘[email protected]’, ‘location’: ‘Gurgaon’}

Traceback (most recent call last):

  File “main.py”, line 7, in <module>

    print(my_dict)

NameError: name ‘my_dict’ is not defined

The dict.pop() method is also used to delete elements from a dictionary. Using the built-in pop() method, you can easily delete an element based on its given key. The syntax is:

The pop() method returns the value of the removed key. In case of the absence of the given key, it will return the default value. If neither the default value nor the key is present, it will give an error. 

Here’s an example that shows the deletion of elements using dict.pop() –

It is easy to append elements to the existing dictionary using the dictionary name followed by square brackets with a key inside it and assigning a value to it. 

Here’s an example:

{‘username’: ‘ABC’, ’email’: ‘[email protected]’, ‘location’: ‘Gurgaon’, ‘name’: ‘Nick’}

For updating the existing elements in a dictionary, you need a reference to the key whose value needs to be updated. 

In this example, we will update the username from ABC to XYZ. Here’s how to do it:

{‘username’: ‘XYZ’, ’email’: ‘[email protected]’, ‘location’: ‘Gurgaon’}

Let us consider an example with two dictionaries – Dictionary 1 and Dictionary 2 as shown below –

Dictionary 1:

my_dict = {“username”: “ABC”, “email”: “abc@gmail.com”, “location”:”Gurgaon”}

Dictionary 2:

my_dict1 = {“firstName” : “Nick”, “lastName”: “Jonas”}

Now we want to merge Dictionary 1 into Dictionary 2. This can be done by creating a key called “name” in my_dict and assigning my_dict1 dictionary to it. Here’s how to do it:

{‘username’: ‘ABC’, ’email’: ‘[email protected]’, ‘location’: ‘Gurgaon’, ‘name’: {‘firstName’: ‘Nick’, ‘lastName’: Jonas}}

As observed in the output, the key ‘name’ has the dictionary my_dict1. 

• Restrictions on Key Dictionaries:

Python dictionaries have some restrictions on their keys. Here are some examples of invalid dictionary keys:

• How to append an element to a key in a dictionary with Python:

You can append an element to a list that is a value associated with a key in a dictionary like this:

• Accessing elements of a dictionary:

You can access elements in a dictionary using their keys like this:

You can also use the get() method to access dictionary elements. This method returns None if the key is not present in the dictionary:

• Deleting element(s) in a dictionary:

You can delete an element from a dictionary using the del keyword like this:

• Deleting Element(s) from dictionary using pop() method:

You can also delete an element from a dictionary using the pop() method. This method removes the key-value pair from the dictionary and returns the value:

• Appending element(s) to a dictionary:

You can append a new key-value pair to a dictionary like this:

• Updating existing element(s) in a dictionary:

You can update an existing element in a dictionary by assigning a new value to its key like this:

• Insert a dictionary into another dictionary:

You can insert a dictionary into another dictionary by using the update() method like this:

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Yes, you can append to a dictionary in Python. It is done using the update() method. The update() method links one dictionary with another, and the method involves inserting key-value pairs from one dictionary into another dictionary. 

You can add data or values to a dictionary in Python using the following steps: First, assign a value to a new key. Use dict. Update() method to add multiple values to the keys. Use the merge operator (I) if you are using Python 3.9+  Create a custom function 

Yes, append works for dictionaries in Python. This can be done using the update() function and [] operator. 

To append to a dictionary key in Python, use the following steps: 1. Converting an existing key to a list type to append value to that key using the append() method. 2. Append a list of values to the existing dictionary’s keys.

Appending an empty dictionary means adding a key-value pair to that dictionary. This can be done using the dict[key] method.  Here’s how to do it: a_dict = {} a_dict[“key”] = “value” print(a_dict) The output is: {‘key’: ‘value’}

Using the update() function and [] operator, you can add or append a new key value to the dictionary. This method can also be used to replace the value of any existing key or append new values to the keys. 

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Assign a dictionary Key or Value to variable in Python

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

# 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.

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.

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.

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
• Divide each value in a Dictionary by total value 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
• Swap the keys and values in a Dictionary in Python

Borislav Hadzhiev

Web Developer

Copyright © 2023 Borislav Hadzhiev

Python Dictionary Append: How to Add Key/Value Pair

The keys in a dictionary are unique and can be a string, integer, tuple, etc. The values can be a list or list within a list, numbers, string, etc.

Here is an example of a dictionary:

Restrictions on Key Dictionaries

Here is a list of restrictions on the key in a dictionary:

• If there is a duplicate key defined in a dictionary, the last is considered. For example consider dictionary my_dict = {“Name”:”ABC”,”Address”:”Mumbai”,”Age”:30, “Name”: “XYZ”};. It has a key “Name” defined twice with value as ABC and XYZ. The preference will be given to the last one defined, i.e., “Name”: “XYZ.”
• The data-type for your key can be a number, string, float, boolean, tuples, built-in objects like class and functions. For example my_dict = {bin:”001″, hex:”6″ ,10:”ten”, bool:”1″, float:”12.8″, int:1, False:’0′};Only thing that is not allowed is, you cannot defined a key in square brackets for example my_dict = {[“Name”]:”ABC”,”Address”:”Mumbai”,”Age”:30};

How to append an element to a key in a dictionary with Python?

We can make use of the built-in function append() to add elements to the keys in the dictionary. To add element using append() to the dictionary, we have first to find the key to which we need to append to.

Consider you have a dictionary as follows:

The keys in the dictionary are Name, Address and Age. Usingappend() methodwe canupdate the values for the keys in the dictionary.

When we print the dictionary after updating the values, the output is as follows:

Accessing elements of a dictionary

The data inside a dictionary is available in a key/value pair. To access the elements from a dictionary, you need to use square brackets ([‘key’]) with the key inside it.

Here is an example that shows to accesselements from the dictionary by using the key in the square bracket.

If you try to use a key that is not existing in the dictionary , it will throw an error as shown below:

Deleting element(s) in a dictionary

To delete an element from a dictionary, you have to make use of the del keyword.

The syntax is :

To delete the entire dictionary, you again can make use of the del keyword as shown below:

To just empty the dictionary or clear the contents inside the dictionary you can makeuse of clear() method on your dictionaryas shown below:

Here is a working example that shows the deletion of element, to clear the dict contents and to delete entire dictionary.

Deleting Element(s) from dictionary using pop() method

In addition to the del keyword, you can also make use of dict.pop() method to remove an element from the dictionary. The pop() is a built-in method available with a dictionary that helps to delete the element based on the key given.

The pop() method returns the element removed for the given key, and if the given key is not present, it will return the defaultvalue. If the defaultvalue is not given and the key is not present in the dictionary, it will throw an error.

Here is a working example that shows using of dict.pop() to delete an element.

Appending element(s) to a dictionary

To append an element to an existing dictionary, you have to use the dictionary name followed by square brackets with the key name and assign a value to it.

Here is an example of the same:

Updating existing element(s) in a dictionary

To update the existing elements inside a dictionary, you need a reference to the key you want the value to be updated.

So we have a dictionary my_dict = {“username”: “XYZ”, “email”: “xyz@gmail.com”, “location”:”Mumbai”}.

We would like to update the username from XYZ to ABC . Here is an example that shows how you can update it.

Insert a dictionary into another dictionary

Consider you have two dictionaries as shown below:

Dictionary 1:

Dictionary 2:

Now I want my_dict1 dictionary to be inserted into my_dict dictionary. To do that lets create a key called “name” in my_dict and assign my_dict1 dictionary to it.

Here is a working example that shows inserting my_dict1 dictionary into my_dict.

Now if you see the key “name”, it has the dictionary my_dict1.

• Dictionary is one of the important data types available in Python. The data in a dictionary is stored as a key/value pair. The key/value is separated by a colon(:), and the key/value pair is separated by comma(,). The keys in a dictionary are unique and can be a string, integer, tuple, etc. The values can be a list or list within a list, numbers, string, etc. When working with lists, you might want to sort them. In that case, you can learn more about Python list sorting in this informative article.

Important built-in methods on a dictionary:

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• Write For US

Python Add keys to Dictionary

• Post author: AlixaProDev
• Post category: Python / Python Tutorial
• Post last modified: February 24, 2023

Python provides several ways to add new keys to a dictionary. Dictionaries are data type in python, that allows you to store key-value pairs. To add keys to the dictionary in Python, you can use the square bracket notation, the update() method, the dict.setdefault() method, and dictionary unpacking. In this article, we’ll explain these methods with examples.

Methods to Add Keys to Dictionary

• Using the [] Notation
• Using the update() Method
• Using the setdefault() Method
• Using the dict() Constructor
• Using Dictionary Comprehension
• Comparision – The Best Method
• Summary and Conclusion

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1. Quick Examples to Add New Keys to Dictionary

Before we explore the various ways to add new keys to a dictionary in Python, let’s take a quick look at some examples.

2. Using the [] Notation

One of the simplest and most commonly used approaches to add new keys to a Python dictionary is using the [] notation. The advantage of this approach is its simplicity and readability. It is a very efficient method in terms of performance, as it does not require the use of any additional functions or methods.

Yields the following output:

It is worth noting that if the key already exists in the dictionary, it will overwrite the existing key with the new value.

3. Using the update() Method

The update() method is another commonly used approach to add new keys to a Python dictionary. This method takes a dictionary as an argument and adds the key-value pairs from that dictionary to the original dictionary.

If a key already exists in the original dictionary, its value will be updated with the value from the argument dictionary. One advantage of the update() method is that it allows for the addition of multiple key-value pairs at once.

It is important to note that the update() method modifies the original dictionary in place, which may not always be desirable.

4. Using the setdefault() Method

The setdefault() method is a dictionary method that provides a convenient way to add new keys to a dictionary without overwriting existing keys. This method takes two arguments: the first argument is the key that you want to add, and the second argument is the default value for that key.

If the key is already in the dictionary, setdefault() will simply return the existing value.

5. Using the dict() Constructor

The dict() constructor in Python can also be used to add new keys to a dictionary. This method creates a new dictionary object and allows you to specify key-value pairs using keyword arguments.

If you pass in a key that already exists in the dictionary, its value will be updated. Otherwise, a new key-value pair will be added to the dictionary.

6. Using Dictionary Comprehension

Dictionary comprehension is a concise and elegant way to create dictionaries in Python. It is a one-liner for-loop that iterates over a sequence of items and creates a dictionary based on the key-value pairs returned by the loop.

Using dictionary comprehension, you can also add new key-value pairs to an existing dictionary. To do this, you simply add a conditional expression to the comprehension that specifies the new key-value pairs.

You can create a new dictionary from an iterable object like a list, and specify the key-value pairs using a simple expression. You can then merge this new dictionary with an existing dictionary using the unpacking operator ** .

7. Comparision – The Best Method

Adding new keys to a dictionary in Python, there are several methods available, each with its own advantages and disadvantages. After running multiple tests on different methods to add new keys to a dictionary, the [] notation method was found to be the fastest.

This is because it involves a direct reference to the dictionary and a simple assignment statement, which is a straightforward and efficient operation.

Yields the following output on my system but it may vary on your system.

8. Summary and Conclusion

Adding new keys to a Python dictionary is a common task in many programs. We discussed [] notation, update() method, setdefault() method, dict() constructor, and dictionary comprehension. I hope this article has provided you with a good understanding of how to add new keys to a dictionary in Python using different methods. If you have any further questions comment below.

Happy coding!

You may also like reading:

• Python Iterate Over A Dictionary
• Python Dictionary Comprehension Explained
• How to Create Nested Dictionary in Python
• Python Sort Dictionary by Key
• Get All Keys from Dictionary in Python
• Python Remove Element from Dictionary
• Append Item to Dictionary in Python
• Sort Python Dictionary Explained with Examples
• Convert Two Lists into Dictionary in Python
• Copy the Dictionary and edit it in Python

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