Python put into dict

Python Dictionary Append: How to Add Key/Value Pair

Dictionary is one of the important data types available in Python. The data in a dictionary is stored as a key/value pair. It 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.

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 = ;. 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 = ;Only thing that is not allowed is, you cannot defined a key in square brackets for example my_dict = ;

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.

my_dict = <"Name":[],"Address":[],"Age":[]>; my_dict["Name"].append("Guru") my_dict["Address"].append("Mumbai") my_dict["Age"].append(30) print(my_dict)

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.

my_dict = print("username :", my_dict['username']) print("email : ", my_dict["email"]) print("location : ", my_dict["location"])

username : XYZ email : xyz@gmail.com location : Mumbai

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

my_dict = print("name :", my_dict['name'])

Traceback (most recent call last): File "display.py", line 2, in print("name :", my_dict['name']) KeyError: 'name'

Deleting element(s) in a dictionary

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

del dict['yourkey'] # This will remove the element with your key.

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

del my_dict # this will delete the dictionary with name my_dict

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.

my_dict = del my_dict['username'] # it will remove "username": "XYZ" from my_dict print(my_dict) my_dict.clear() # till will make the dictionarymy_dictempty print(my_dict) delmy_dict # this will delete the dictionarymy_dict print(my_dict)

 <> Traceback (most recent call last): File "main.py", line 7, in print(my_dict) NameError: name 'my_dict' is not defined

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.

my_dict = my_dict.pop("username") print(my_dict)

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:

my_dict = my_dict['name']='Nick' print(my_dict)

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.

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

my_dict = my_dict["username"] = "ABC" print(my_dict)

Insert a dictionary into another dictionary

Consider you have two dictionaries as shown below:

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.

my_dict = my_dict1 = my_dict["name"] = my_dict1 print(my_dict)

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

Summary

• 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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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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Словари (dict) и работа с ними. Методы словарей

Сегодня я расскажу о таком типе данных, как словари, о работе со словарями, операциях над ними, методах, о генераторах словарей.

Словари в Python — неупорядоченные коллекции произвольных объектов с доступом по ключу. Их иногда ещё называют ассоциативными массивами или хеш-таблицами.

Чтобы работать со словарём, его нужно создать. Сделать это можно несколькими способами. Во-первых, с помощью литерала:

Во-вторых, с помощью функции dict:

В-третьих, с помощью метода fromkeys:

В-четвертых, с помощью генераторов словарей, которые очень похожи на генераторы списков.

Теперь попробуем добавить записей в словарь и извлечь значения ключей:

  : Как видно из примера, присвоение по новому ключу расширяет словарь, присвоение по существующему ключу перезаписывает его, а попытка извлечения несуществующего ключа порождает исключение. Для избежания исключения есть специальный метод (см. ниже), или можно перехватывать исключение.

Что же можно еще делать со словарями? Да то же самое, что и с другими объектами: встроенные функции, ключевые слова (например, циклы for и while), а также специальные методы словарей.

Методы словарей

dict.clear() — очищает словарь.

dict.copy() — возвращает копию словаря.

classmethod dict.fromkeys(seq[, value]) — создает словарь с ключами из seq и значением value (по умолчанию None).

dict.get(key[, default]) — возвращает значение ключа, но если его нет, не бросает исключение, а возвращает default (по умолчанию None).

dict.items() — возвращает пары (ключ, значение).

dict.keys() — возвращает ключи в словаре.

dict.pop(key[, default]) — удаляет ключ и возвращает значение. Если ключа нет, возвращает default (по умолчанию бросает исключение).

dict.popitem() — удаляет и возвращает пару (ключ, значение). Если словарь пуст, бросает исключение KeyError. Помните, что словари неупорядочены.

dict.setdefault(key[, default]) — возвращает значение ключа, но если его нет, не бросает исключение, а создает ключ со значением default (по умолчанию None).

dict.update([other]) — обновляет словарь, добавляя пары (ключ, значение) из other. Существующие ключи перезаписываются. Возвращает None (не новый словарь!).

dict.values() — возвращает значения в словаре.

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