Python dict get any key

Python dictionary find a key by value

In this Python tutorial, we will learn about the Python dictionary to find a key by value. Also, we will discuss the below examples:

• Python dictionary find key by max value.
• Python dictionary get Key value by index
• Python dictionary find key using value
• Python dictionary get key value pair
• Python dictionary find key with maximum value
• Python dictionary get key if value exists

Python dictionary find a key by value

• Here we can see how to get the key by value in Python.
• We can perform this task by various methods, Here is the list of some that we can use.
  • By using list.index()
  • By using dict.items() method
  • By using list comprehension method

  By using list.index() method

  The index method always returns the index position in a list or dictionary.

  Source Code:

  to_dictionary = new_ke_lis = list(to_dictionary.keys()) new_val = list(to_dictionary.values()) new_pos = new_val.index(610) # value from dictionary print("Get a key by value:",new_ke_lis[new_pos])

  Here is the Screenshot of the following given code

  

  By using dict.items() method

  This method returns a dictionary view object that displays the list of a dictionary in the key-value pair form.

  my_dict= for key,value in my_dict.items(): if value==9: print("key by value:",key)

  

  By using list comprehension method

  In Python to get the key with the maximum value, we can use the list comprehension method. This method will help the user to execute each element along with the for loop to iterate each item.

  new_dictionary= t= print("key by value:",t)

  

  Python dictionary find key by max value

  • Let us see how to find the key by the maximum value.
  • By using the max() function we will find the key with maximum value in Dictionary.
  • To do this task first we will initialize a dictionary and assign them a key-value pairs element. Now use a max() function to get the key with maximum value.

  new_dict= new_ke = max(new_dict, key=new_dict.get) print("To get Key maxvalue:",new_ke)

  Here is the implementation of the following given code

  

  Another example to get the key with max value

  By using the itemgetter() function and operator module we can easily get the key. The itemgetter() function returns an object that collects an item from its operand using the operator module.

  Let’s take an example and check how to get the key by using the itemgetter() function.

  import operator my_dict1 = new_max_key = max(my_dict1.items(), key = operator.itemgetter(1))[0] print("key with highest value:\n",new_max_key)

  Here is the Screenshot of the following given code

  

  By using lambda function

  In Python, the lambda function did not need any name, they are nameless. They are used to declare a one-line function. In this example, you just need to give the function a value and then provide an expression.

  In this example, we have to check how to find a key with maximum value using the lambda function

  my_dict2 = ma_value = max(my_dict2, key= lambda i: my_dict2[i]) print(ma_value)

  

  Python dictionary get key value by index

  • Let us see how to get a key-value pair by index in the dictionary.
  • To perform this task we can use the enumerator method. This is an in-built function in Python that allows the user to check how many iterations have occurred. This method can be used directly for loops and convert them into a list.
  • Let’s take an example and check how to get key-value pair by index.

  my_new_dict = get_key = 'i' new_search_key='l' new_var = list(my_new_dict.items()) output = [ab for ab, new_key in enumerate(new_var) if new_key[0] == get_key] result2 = [ab for ab, new_key in enumerate(new_var) if new_key[0] == new_search_key] print("Get index value of key : ",output) print("Get index value of key : ",result2) 

  Here is the execution of the following given code

  

  Another example to check how to get key-value index by using dict() method

  Source Code:

  dict1 = ind_lis = list(dict1) new_key = ind_lis[1] print("Get key-value by index:",new_key)

  Here is the Output of the following given code

  

  Python dictionary find key using value

  In Python to find a key using the value, we can collect the key from a value by comparing all the values and get the specific key. In this example, we can use dict.items() method.

  Let’s take an example and check how to find a key by using the value.

  from typing import TextIO def new_ke(val): for k, new_va in to_dictionary.items(): if val == new_va: return k return to_dictionary = print("Key exist in dictionary:",new_ke(72)) print("key doesnot contain in dictionary:",new_ke(48))

  Here is the Screenshot of the following given code

  

  Python dictionary get key value pair

  • To get key-value pair in the dictionary we can easily use the enumerator method.
  • This method helps the user to access the named index of the position of the key-value element in the dictionary.

  dictionary1 = for x in enumerate(dictionary1.items()): print("key-value pair in dictionary:",x)

  Here is the implementation of the following given code

  

  Another example to check how to get key value pair

  To perform this particular task we can easily use the list comprehension method. This method returns the elements in the form of key-value pairs and it will display the result as tuples of key and value in the list.

  you_dictionary = print ("key-value pairs are : ") print([(m, you_dictionary[m]) for m in you_dictionary])

  Here is the Screenshot of the following given code

  

  Python dictionary find key with maximum value

  To find the key with the maximum value we can easily use the function values() and keys().

  to_dict2 = new_value = list(to_dict2.values()) new_key = list(to_dict2.keys()) print(new_key[new_value.index(max(new_value))])

  Here is the execution of the following given code

  

  Python dictionary get key if value exist

  from typing import TextIO def exe_ke(val): for x, new_va in your_dict.items(): if val == new_va: return x return your_dict = print("Value exist in dictionary:",exe_ke(149)) print("value doesnot exist in dictionary:",exe_ke(456))

  

  You may also like reading the following articles.

  In this Python tutorial, we have learned about the Python dictionary to find a key by value. Also, we have also discussed the below examples:

  • Python dictionary find key by max value.
  • Python dictionary get Key value by index
  • Python dictionary find key using value
  • Python dictionary get key value pair
  • Python dictionary find key with maximum value

  I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.

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  Get key from value in dictionary in Python

  This article explains how to get the key from the value in a dictionary ( dict ) in Python.

  To get the value by the key, simply specify the key as follows.

  d = 'key1': 'aaa', 'key2': 'aaa', 'key3': 'bbb'> value = d['key1'] print(value) # aaa 

  You can also use the get() method to get the value by the key. When using the get() method, no error will be raised even if you specify a non-existent key. See the following article.

  You can also use the keys() method to get a list of all keys.

  Get key from value with list comprehension and items()

  To get the key from the value in the dictionary, use list comprehension and the items() method.

  For more information on list comprehensions and using for loops with dictionaries, refer to the following articles.

  The following sample code demonstrates how to get a list of keys associated with a specified value. If no key with the specified value exists, an empty list is returned.

  d = 'key1': 'aaa', 'key2': 'aaa', 'key3': 'bbb'> 

  keys = [k for k, v in d.items() if v == 'aaa'] print(keys) # ['key1', 'key2'] keys = [k for k, v in d.items() if v == 'bbb'] print(keys) # ['key3'] keys = [k for k, v in d.items() if v == 'xxx'] print(keys) # [] 

  To get the key itself instead of the list, you can access the first element of the list using [0] .

  Note that if no key with the specified value exists, it will be an empty list, so specifying [0] will raise IndexError .

  key = [k for k, v in d.items() if v == 'aaa'][0] print(key) # key1 key = [k for k, v in d.items() if v == 'bbb'][0] print(key) # key3 # key = [k for k, v in d.items() if v == 'xxx'][0] # print(key) # IndexError: list index out of range 

  If you need to perform the same operation multiple times, it’s helpful to create a function.

  def get_keys_from_value(d, val): return [k for k, v in d.items() if v == val] keys = get_keys_from_value(d, 'aaa') print(keys) # ['key1', 'key2'] 

  The following function can also be used for dictionaries without duplicate values.

  If a key with the specified value exists, that key is returned; otherwise, None is returned. If the values are duplicated, one of the keys is returned.

  def get_key_from_value(d, val): keys = [k for k, v in d.items() if v == val] if keys: return keys[0] return None key = get_key_from_value(d, 'aaa') print(key) # key1 key = get_key_from_value(d, 'bbb') print(key) # key3 key = get_key_from_value(d, 'xxx') print(key) # None 

  Sample codes to extract keys with various conditions

  In the examples above, keys with values equal to the specified value are extracted.

  To extract keys under different conditions, modify the conditional expression in the list comprehension.

  d_num = 'key1': 1, 'key2': 2, 'key3': 3> keys = [k for k, v in d_num.items() if v >= 2] print(keys) # ['key2', 'key3'] keys = [k for k, v in d_num.items() if v % 2 == 1] print(keys) # ['key1', 'key3'] d_str = 'key1': 'aaa@xxx.com', 'key2': 'bbb@yyy.net', 'key3': 'ccc@zzz.com'> keys = [k for k, v in d_str.items() if v.endswith('com')] print(keys) # ['key1', 'key3'] 

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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.

  Для вставки кода на Python в комментарий заключайте его в теги

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