Python dict values to dictionary

Python – Update dictionary with other dictionary

Sometimes, while working with Python dictionaries, we can have problem in which we need to perform the update of dictionary with other keys of dictionary. This can have applications in domains in which we need to add certain records to previously captured records. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using loop This is a brute force way in which this task can be performed. In this, we check for keys in other dictionary, and add the items in new dictionary.

Python3

The original dictionary 1 is : The original dictionary 2 is : The updated dictionary is :

Method #2 : Using dictionary comprehension This is yet another way in which this task can be performed. In this, we iterate for dictionary and perform update in single line using comprehension.

Python3

The original dictionary 1 is : The original dictionary 2 is : The updated dictionary is :

The time complexity of the given program is O(N), where N is the total number of keys in both the dictionaries.

The space complexity of the program is also O(N), where N is the number of keys in test_dict1.

Method #3 : Using update() method

Python3

The original dictionary 1 is : The original dictionary 2 is : The updated dictionary is :

Time Complexity : O(N)

Auxiliary Space : O(N)

Method #4: Using the’ **’ operator: The ‘**’ operator

1. Define the two dictionaries:
2. Print the original dictionaries to verify their contents:
3. Use the “**” operator to combine the dictionaries into a new dictionary:
4. Print the updated dictionary to verify the combination:
5. The output should show the updated dictionary with the combined key-value pairs:

Python3

# The «**» operator is used to unpack dictionaries and pass the key-value pairs as separate arguments to a function

# In this case, we are using the «**» operator to unpack the dictionaries and add their key-value pairs to a new dictionary

The original dictionary 1 is : The original dictionary 2 is : The updated dictionary is :

Time Complexity: Creating the DataFrame object takes O(n) time, where n is the length of the first list.
Extracting the values from the first list corresponding to the indices in the second list using the loc[] function takes O(m) time, where m is the length of the second list.

Converting the resulting series object to a list takes O(m) time.
Therefore, the overall time complexity of the algorithm is O(n+m).

Auxiliary Space Complexity: The algorithm uses O(n) auxiliary space to store the DataFrame object and O(m) auxiliary space to store the resulting list. Therefore, the overall auxiliary space complexity of the algorithm is O(n+m). Note that this assumes that the length of the resulting list is at most min(n,m); if the length of the resulting list can be greater than min(n,m), then the overall auxiliary space complexity would be O(max(n,m)).

Method #6: Using the dict() constructor and the update() method

Use the dict() constructor to create a copy of the first dictionary and then updates it with the second dictionary using the update() method.

Python3

The original dictionary 1 is : The original dictionary 2 is : The updated dictionary is :

Time complexity: O(N), where N is the total number of key-value pairs in both dictionaries.
Auxiliary space: O(N)

Method #7: Using reduce():

1. Import the reduce() function from the functools module.
2. Initialize the two dictionaries to be merged.
3. Define a lambda function that takes two arguments: an accumulator dictionary and the next dictionary to merge, and returns a new dictionary that is the result of merging the accumulator dictionary with the next dictionary using the unpacking syntax **.
4. Use the reduce() function to apply the lambda function to each dictionary in the list of dictionaries to be merged, starting with the first dictionary as the initial accumulator value.
5. Return the final merged dictionary.

Python3

The original dictionary 1 is : The original dictionary 2 is : The updated dictionary is :

Time complexity:

The reduce() function is applied to each dictionary in the list, so the time complexity of the reduce() function is O(N), where N is the number of dictionaries in the list.
Merging two dictionaries using the unpacking syntax ** takes O(M) time, where M is the number of key-value pairs in the smaller dictionary.
Therefore, the total time complexity of the algorithm is O(N * M), where N is the number of dictionaries in the list and M is the maximum number of key-value pairs in any dictionary.

Auxiliary Space:

The space complexity of the algorithm depends on the size of the dictionaries being merged and the number of dictionaries in the list.
Since the lambda function returns a new dictionary every time it is called, the space complexity is proportional to the total size of the merged dictionary.
Therefore, the space complexity of the algorithm is O(K), where K is the total number of key-value pairs in all the dictionaries being merged.

Method #8: Using heapq:

1. Create two dictionaries test_dict1 and test_dict2.
2. Convert both dictionaries into tuples of (value, key) pairs with the help of a list comprehension.
3. Create a list of the two tuple lists created above.
4. Use the heapq.merge() function to merge the tuple lists.
5. The merged tuples will be in ascending order of values, so we negate the values while merging to get the desired descending order.
6. Convert the merged tuples back to a dictionary with the key as the second element of each tuple and the value as the negation of the first element of each tuple.
7. Print the updated dictionary.

Источник

Python | Add dictionary to dictionary without overwriting

In this article, we will discuss how to add the contents of a dictionary to another dictionary without overwriting values of similar keys.

Suppose we have two dictionaries with some similar keys. Like this,

dict_1 and dict_2 have following common keys – ‘test’, ‘at’, ‘Hello’. Now we want to add the contents of a dictionary dict_2 to dictionary dict_1. But instead of overwriting values for common keys, we want to merge the values of common keys while adding. For example, after adding the contents of dict_2 to dict_1, the final content of dict_1 should be like this,

Values of similar keys from both the dictionaries should persist in a list after merging. Let’s see how to do that,

Add dictionary to dictionary without overwriting in Python.

Directly calling the dictionary’s update() function with another dictionary as a argument i.e. dict_1.update(dict_2), will update the existing values of common key. So, instead of it, we will do the following steps,

Frequently Asked:

• Iterate over all key-value pairs of dictionary dict_2 in a loop
• During iteration, for each key-value pair, check if key already exist in dictionary dict_1 or not.
  • If the key already exists in dict_1 and the value for that key is not of list type, create a list and add both values of that key from dict_1 & dict_2 to it. Then replace the current value of that key in dict_1 with this list.
  • If the key already exists in dict_1 and it is has a value of list type. Then append the value of this key from dict_2 to that list value in dict_1.
  • If the key doesn’t exist in dict_1, then add this key-value pair to dict_1.

  Let’s understand by an example,

  dict_1 = < "Hello": 56, "at": 23, "test": 43, "this": 12 >dict_2 = < 'test': 4, 'at': 5, 'why': 6, 'Hello': 20 >for key, value in dict_2.items(): if key in dict_1: if isinstance(dict_1Python dict values to dictionary, list): dict_1Python dict values to dictionary.append(value) else: temp_list = [dict_1Python dict values to dictionary] temp_list.append(value) dict_1Python dict values to dictionary = temp_list else: dict_1Python dict values to dictionary = value print(dict_1)

  Here, we added all the key-value pairs of dictionary dict_2 to another dictionary dict_1. Both dict_1 and dict_2 had similar keys, and for those keys, the values from dict_2 got added along with the existing values from dict_1. So, nothing got overwritten while adding a dictionary to another dictionary.

  We learned a way to all contents of a dictionary to another dictionary without overwriting the values of similar keys.

  Related posts:

  Share your love

  Leave a Comment Cancel Reply

  This site uses Akismet to reduce spam. Learn how your comment data is processed.

  Terms of Use

  Disclaimer

  Copyright © 2023 thisPointer

  To provide the best experiences, we and our partners use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us and our partners to process personal data such as browsing behavior or unique IDs on this site and show (non-) personalized ads. Not consenting or withdrawing consent, may adversely affect certain features and functions.

  Click below to consent to the above or make granular choices. Your choices will be applied to this site only. You can change your settings at any time, including withdrawing your consent, by using the toggles on the Cookie Policy, or by clicking on the manage consent button at the bottom of the screen.

  The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.

  The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.

  The technical storage or access that is used exclusively for statistical purposes. The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.

  The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.

  Источник

  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.

  Для вставки кода на Python в комментарий заключайте его в теги

  Источник

  Читайте также:  Meta name html function