Python add object to dictionary

Python Add to Dictionary: A Guide

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We’ll break down the basics of dictionaries, how they work, and how you can add an item to a Python dictionary. By the end of this tutorial, you’ll be an expert at adding items to Python dictionaries.

Python Dictionary: A Refresher

The dictionary data structure allows you to map keys to values. This is useful because keys act as a label for a value, which means that when you want to access a particular value, all you have to do is reference the key name for the value you want to retrieve.

Dictionaries generally store information that is related in some way, such as a record for a student at school, or a list of colors in which you can purchase a rug.

Consider the following dictionary:

This dictionary contains four keys and four values. The keys are stored as a string, and appear to the left of the colon; the values are stored to the right of the colons; bound to a particular key in the dictionary.

Now, how do we add an item to this dictionary? Let’s break it down.

Python Add to Dictionary

To add an item to a Python dictionary, you should assign a value to a new index key in your dictionary.

Unlike lists and tuples, there is no add() , insert() , or append() method that you can use to add items to your data structure. Instead, you have to create a new index key, which will then be used to store the value you want to store in your dictionary.

Here is the syntax for adding a new value to a dictionary:

dictionary_namePython add object to dictionary = value

Let’s use an example to illustrate how to add an item to a dictionary. In our dictionary from earlier, we stored four keys and values. This dictionary reflected the stock levels of different flavors of scones sold at a cafe.

Suppose we have just baked a batch of 10 new cherry scones. Now, we want to add these scones to our dictionary of scone types. To do so, we can use this code:

scones = < "Fruit": 22, "Plain": 14, "Cinnamon": 4, "Cheese": 21 >scones["Cherry"] = 10 print(scones)

As you can see, our code has added the “Cherry” key to our dictionary, which has been assigned the value 10.

In our code, we first declared a dictionary called “scones” which stores information on how many scones are available at a cafe to order. Next, we added the key “Cherry” to our dictionary and assigned it the value 10 by using the following code:

Finally, we printed out the updated version of our dictionary.

Notice that, in the output of our code, our dictionary is not ordered. This is because data stored in a dictionary, unlike data stored in a list, does not have any particular order.

Tip: Adding and Updating Use the Same Notation

The same notation can be used to update a value in a dictionary. Suppose we have just baked a new batch of 10 cinnamon scones. We could update our dictionary to reflect this using the following line of code:

scones = < "Fruit": 22, "Plain": 14, "Cinnamon": 4, "Cheese": 21 >scones["Cinnamon"] = 14 print(scones)

This line of code sets the value associated with the “Cinnamon” key in our dictionary to 14.

Conclusion

There is no add() , append() , or insert() method you can use to add an item to a dictionary in Python. Instead, you add an item to a dictionary by inserting a new index key into the dictionary, then assigning it a particular value.

This tutorial discussed, with an example, how to add an item to a Python dictionary. Now you’re ready to start adding items to dictionaries like a Python expert!

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James Gallagher is a self-taught programmer and the technical content manager at Career Karma. He has experience in range of programming languages and extensive expertise in Python, HTML, CSS, and JavaScript. James has written hundreds of programming tuto. read more

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Python: Add Key:Value Pair to Dictionary

In this tutorial, you’ll learn how to add key:value pairs to Python dictionaries. You’ll learn how to do this by adding completely new items to a dictionary, adding values to existing keys, and dictionary items in a for loop, and using the zip() function to add items from multiple lists.

What are Python dictionaries? Python dictionaries are incredibly helpful data types, that represent a hash table, allowing data retrieval to be fast and efficient. They consist of key:value pairs, allowing you to search for a key and return its value. Python dictionaries are created using curly braces, <> . Their keys are required to be immutable and unique, while their values can be any data type (including other dictionaries) and do not have to be unique.

The Quick Answer: Use dictPython add object to dictionary = [value] to Add Items to a Python Dictionary

Add an Item to a Python Dictionary

The easiest way to add an item to a Python dictionary is simply to assign a value to a new key. Python dictionaries don’t have a method by which to append a new key:value pair. Because of this, direct assignment is the primary way of adding new items to a dictionary.

Let’s take a look at how we can add an item to a dictionary:

# Add an Item to a Python Dictionary dictionary = dictionary['Evan'] = 30 print(dictionary) # Returns:

We can see here that we were able to easily append a new key:value pair to a dictionary by directly assigning a value to a key that didn’t yet exist.

What can we set as dictionary keys? It’s important to note that we can add quite a few different items as Python dictionary keys. For example, we could make our keys strings, integers, tuples – any immutable item that doesn’t already exist. We can’t, however, use mutable items (such as lists) to our dictionary keys.

In the next section, you’ll learn how to use direct assignment to update an item in a Python dictionary.

Update an Item in a Python Dictionary

Python dictionaries require their keys to be unique. Because of this, when we try to add a key:value pair to a dictionary where the key already exists, Python updates the dictionary. This may not be immediately clear, especially since Python doesn’t throw an error.

Let’s see what this looks like, when we add a key:value pair to a dictionary where the key already exists:

# Update an Item in a Python Dictionary dictionary = dictionary['Nik'] = 30 print(dictionary) # Returns:

We can see that when we try to add an item to a dictionary when the item’s key already exists, that the dictionary simply updates. This is because Python dictionaries require the items to be unique, meaning that it can only exist once.

In the next section, you’ll learn how to use a for loop to add multiple items to a Python dictionary.

Append Multiple Items to a Python Dictionary with a For Loop

There may be times that you want to turn two lists into a Python dictionary. This can be helpful when you get data from different sources and want to combine lists into a dictionary data structure.

Let’s see how we can loop over two lists to create a dictionary:

# Loop Over Two Lists to Create a Dictionary keys = ['Nik', 'Kate', 'Jane'] values = [32, 31, 30] dictionary = <> for i in range(len(keys)): dictionaryPython add object to dictionary] = values[i] print(dictionary) # Returns:

Here, we loop over each value from 0 through to the length of the list minus 1, to access the indices of our lists. We then access the i th index of each list and assign them to the keys and values of our lists.

There is actually a much simpler way to do this – using the Python zip function, which you’ll learn about in the next section.

Add Multiple Items to a Python Dictionary with Zip

The Python zip() function allows us to iterate over two iterables sequentially. This saves us having to use an awkward range() function to access the indices of items in the lists.

Let’s see what this looks like in Python:

# Loop Over Two Lists to Create a Dictionary using Zip keys = ['Nik', 'Kate', 'Jane'] values = [32, 31, 30] dictionary = <> for key, value in zip(keys, values): dictionaryPython add object to dictionary = value print(dictionary) # Returns:

The benefit of this approach is that it is much more readable. Python indices can be a difficult thing for beginner Python developers to get used to. The zip function allows us to easily interpret what is going on with our code. We can use the zip function to name our iterable elements, to more easily combine two lists into a dictionary.

If you’re working with a dictionary that already exists, Python will simply update the value of the existing key. Because Python lists can contain duplicate values, it’s important to understand this behaviour. This can often lead to unexpected results since the program doesn’t actually throw an error.

Conclusion

In this tutorial, you learned how to use Python to add items to a dictionary. You learned how to do this using direct assignment, which can be used to add new items or update existing items. You then also learned how to add multiple items to a dictionary using both for loops and the zip function.

To learn more about Python dictionaries, check out the official documentation here.

Additional Resources

To learn more about related topics, check out the articles below:

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How to add key,value pair to dictionary? [duplicate]

Thanks it’s working..I meant resultset of query. Do you know which are the concerns using python..i don’t know am new of this technology before i have worked in dotnet.

@Krishnasamy: If you have earlier worked on dotnet, Python will be a pleasure to work with. It is as versatile as dotnet and java, if not more

For quick reference, all the following methods will add a new key ‘a’ if it does not exist already or it will update the existing key value pair with the new value offered:

data['a']=1 data.update() data.update(dict(a=1)) data.update(a=1) 

You can also mixing them up, for example, if key ‘c’ is in data but ‘d’ is not, the following method will updates ‘c’ and adds ‘d’

Why is the down vote? The answer is trying to add useful info so viewers can have an alternative answer which IMHO is more comprehensive, could the gentleman/women who down voted pls clarify?

You don’t need to answer this question since its a duplicate — the appropriate way of handling it is by flagging it as a dupe — see more info there How should duplicate questions be handled?

SO really needs to figure out a way to make things surface better. This is down voted for being a duplicate. But it’s the first thing that appears when a user searches. The down vote then starts more conversation, which causes this answer to FURTHER rise in popularity, thereby hiding the original answer. I would have never have found the original answer had this one not existed. So why not just delete this qeustion completely?

I am not sure what you mean by «dynamic». If you mean adding items to a dictionary at runtime, it is as easy as dictionaryPython add object to dictionary = value .

If you wish to create a dictionary with key,value to start with (at compile time) then use (surprise!)

I got here looking for a way to add a key/value pair(s) as a group — in my case it was the output of a function call, so adding the pair using dictionaryPython add object to dictionary = value would require me to know the name of the key(s).

In this case, you can use the update method: dictionary.update(function_that_returns_a_dict(*args, **kwargs)))

Beware, if dictionary already contains one of the keys, the original value will be overwritten.

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