Python add elements to dict python

Python Add to Dictionary – Adding an Item to a Dict

Ihechikara Vincent Abba

Data structures help us organize and store collections of data. Python has built-in data structures like Lists, Sets, Tuples and Dictionaries.

Each of these structures have their own syntax and methods for interacting with the data stored.

In this article, we’ll talk about Dictionaries, their features, and how to add items to them.

How to Create a Dictionary in Python

Dictionaries are made up of key and value pairs nested in curly brackets. Here’s an example of a Dictionary:

In the code above, we created a dictionary called devBio with information about a developer – the developer’s age is quite overwhelming.

Each key in the dictionary – name , age and language – has a corresponding value. A comma separates each key and value pair from another. Omitting the comma throws an error your way.

Before we dive into how we can add items to our dictionaries, let’s have a look at some of the features of a dictionary. This will help you easily distinguish them from other data structures in Python.

Features of a Dictionary

Here are some of the features of a dictionary in Python:

Duplicate Keys Are Not Allowed

If we create a dictionary that has two or multiple identical keys in it, the last key out of them will override the rest. Here’s an example:

We created three keys with an identical key name of name . When we printed our dictionary to the console, the last key having a value of «Chikara» overwrote the rest.

Let’s see the next feature.

Items in a Dictionary Are Changeable

After assigning an item to a dictionary, you can change its value to something different.

devBio = < "name": "Ihechikara", "age": 120, "language": "JavaScript" >devBio["age"] = 1 print(devBio) #

In the example above, we reassigned a new value to age . This will override the initial value we assigned when the dictionary was created.

We can also use the update() method to change the value of items in our dictionary. We can achieve the same result in the last example by using the update() method – that is: devBio.update() .

Items in a Dictionary Are Ordered

By being ordered, this means that the items in a dictionary maintain the order in which they were created or added. That order cannot change.

Prior to Python 3.7, dictionaries in Python were unordered.

In the next section, we will see how we can add items to a dictionary.

How to Add an Item to a Dictionary

The syntax for adding items to a dictionary is the same as the syntax we used when updating an item. The only difference here is that the index key will include the name of the new key to be created and its corresponding value.

Here’s what the syntax looks like: devBio[newKey] = newValue .

We can also use the update() method to add new items to a dictionary. Here’s what that would look like: devBio.update(newKey«: newValue>) .

devBio = < "name": "Ihechikara", "age": 120, "language": "JavaScript" >devBio["role"] = "Developer" print(devBio) #

Above, using the index key devBio[«role»] , we created a new key with the value of Developer .

In the next example, we will use the update() method.

devBio = < "name": "Ihechikara", "age": 120, "language": "JavaScript" >devBio.update() print(devBio) #

Above, we achieved the same result as in the last example by passing in the new key and its value into the update() method – that is: devBio.update() .

Conclusion

In this article, we learned what dictionaries are in Python, how to create them, and some of their features. We then saw two ways through which we can add items to our dictionaries.

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Как добавить элемент в словарь

Перед тем как начинать, попробуйте решить задачку по словарям, чтобы освежить знания, или пропустите этот блок.

Словари — структура данных. Внутри нее хранятся элементы по принципу «ключ-значение».

При работе со словарями у вас, возможно, возникал вопрос — а как добавить элемент в словарь. В этой статье вы найдете ответ.

Также мы поговорим об основах, о том, как словари работают. И конечно же, разберем, как добавить элемент в словарь. К концу статьи вы станете экспертом в этом деле!

Словари. Краткое введение

Структура словаря позволяет вам привязывать ключи к значениям. Это довольно полезно — можно использовать ключ как ярлык. То есть, если вы хотите получить доступ к какому-то значению, вам нужно просто указать соответствующий ключ.

Словари обычно используются для данных, которые связаны друг с другом. Например, журнал посещаемости студента или цвета ковров, которые вы бы хотели купить.

Словарь выглядит следующим образом:

В этом словаре содержится четыре ключа и четыре значения. Ключи хранятся в виде строки и находятся в левом столбце. Значения же хранятся в правом столбце и привязаны к соответствующим ключам.

И все же — как добавить элемент в словарь? Давайте разберемся.

Как добавить элемент в словарь

Чтобы добавить элемент в словарь, вам нужно привязать значение к новому ключу.

В отличие от списков и кортежей, в работе со словарями методы add() , insert() и append() вам не помощники. Тут необходимо создать новый ключ. Позже он будет использоваться для хранения значения.

Добавляются элементы в словарь так:

dictionary_namePython add elements to dict python = value

Рассмотрим пример, чтобы разобраться. В нашем словаре было четыре пары ключ-значение. Этот словарь отражает количество булочек, которые продаются в кафе.

Допустим, мы испекли 10 вишневых булочек. Теперь нам нужно внести их в словарь. Сделать это можно так:

scones = < "Фрукты": 22, "Пустая": 14, "Корица": 4, "Сыр": 21 >scones["Вишня"] = 10 print(scones)

Как видите, мы добавили в словарь ключ Вишня и присвоили ему значение 10.

Сперва мы объявили словарь scones , хранящий информацию о булочках, которые доступны к заказу в нашем кафе. Потом мы добавили в наш словарь ключ Вишня и присвоили ему значение 10:

И, наконец, мы вывели в консоль обновленную версию словаря.

Заметьте, что в выводе наш словарь не упорядочен. Это происходит из-за того, что данные, хранящиеся в словаре, в отличие от списка, не упорядочены.

Совет: добавление и обновление происходит одинаково

Тем же способом мы можем обновить значение ключа. Допустим, мы испекли еще 10 булочек с корицей. Обновить значение этого ключа можно так:

scones = < "Фрукты": 22, "Пустая": 14, "Корица": 4, "Сыр": 21 >scones["Корица"] = 14 print(scones)

То есть, тем же способом мы можем установить новое значение какому-либо ключу. В нашем случае мы присвоили Корица значение 14.

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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 elements to dict python = [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 elements to dict python] = 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 elements to dict python = 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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