Find key for value python

How to find key from value in python dictionary

In the Python programming language, List, Tuple, and Set represent a group of individual objects as a single entity. If we want to represent a group of objects as key-value pairs then we should go for the Dictionary concept. In this tutorial, we will learn how to get keys from values in the python dictionary using the built-in functions such as items() function, comprehension method, and using the for loop by index() method. The items() method returns the list of tuples representing key-value pairs. [(k,v),(k,v),(k,v)].

Example: Find Dictionary Key using Value

The below example shows how to get keys from a specific value.

# dictionary with key value pairs dict_1 = print("Print only keys:") for i in dict_1: print("The key is:",i) print("Print only values:") for i in dict_1: print("Associated values with keys:",dict_1[i]) print("Getting keys from the specified value") for i in dict_1: if dict_1[i] == "Python": print("The keys associated with value", dict_1[i], "is:", i) 

Once we run the program, it shows the following result.

Print only keys:
The key is: 100
The key is: 200
The key is: 300
The key is: 400
The key is: 500
Print only values:
Associated values with keys: python
Associated values with keys: Java
Associated values with keys: Ruby
Associated values with keys: Python
Associated values with keys: Python
Getting keys from the specified value
The keys associated with value Python is: 400
The keys associated with value Python is: 500

Example: Using the Comprehension Method

The comprehension concept is also applicable to dictionary data types. This is a simple method, we can get keys from values in a single code.

dict_1= x= print("The keys associated with value:",x)

Once we run the code, it shows the following result.

The keys associated with value:

Example: Find key using the item() Method

The below example shows how to get keys from the values using the item() method.

dict_1= for k,v in dict_1.items(): if v=="Java": print("The keys are:",k)

The keys are: 100
The keys are: 200
The keys are: 400

Conclusion

In this tutorial, we learned how to get the keys from a value using the python built-in function, comprehension method, and using the for loop.

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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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  Как получить ключ по значению в словаре в Python

  В Python мы можем получить значения, присутствующие в словаре, по их ключам. Для этого используется синтаксис dict_nameFind key for value python . Но мы не можем таким же образом получить ключ по значению.

  В этой статье мы рассмотрим способы, с помощью которых мы можем получить ключ заданного значения в словаре.

  Как получить ключ из пары ключ-значение путем перебора элементов словаря

  Это самый простой способ извлечь ключ по значению. Мы проверяем каждую пару ключ-значение, чтобы найти ключ, связанный с текущим значением.

  Для этой задачи мы будем использовать метод items() . Этот словарный метод возвращает список кортежей, содержащих пары ключ-значение. В полученном списке мы проверим каждый кортеж, чтобы найти ключ, связанный с нашим значением.

  myDict = print("Dictionary is:") print(myDict) dict_items = myDict.items() print("Given value is:") myValue = "PT" print(myValue) print("Associated Key is:") for key, value in dict_items: if value == myValue: print(key)

  Dictionary is: Given value is: PT Associated Key is: acronym

  Мы создали список элементов в myDict с помощью myDict.items() , а затем проверили каждый элемент в списке, чтобы найти ключ для нашего значения.

  Как получить ключ по значению с помощью списков

  Мы можем создать отдельные списки из ключей и значений, а затем найти ключ нужного значения с помощью метода index() .

  Для этой задачи мы сначала создадим список ключей, имеющихся в словаре, используя метод keys() . Затем создадим список значений, используя метод values() . После этого мы получим индекс нужного значения из списка значений с помощью метода index() .

  Мы знаем, что список ключей имеет тот же порядок ключей, что и значения в списке значений. Поэтому индекс значения в списке значений будет таким же, как и индекс связанного с ним ключа в списке ключей. Таким образом, найдя индекс значения в списке значений, мы можем найти ключ в списке ключей по тому же индексу.

  Это можно сделать следующим образом:

  myDict = print("Dictionary is:") print(myDict) dict_keys = list(myDict.keys()) dict_values = list(myDict.values()) print("Given value is:") myValue = "PT" print(myValue) val_index = dict_values.index(myValue) print("Associated key is:") myKey = dict_keys[val_index] print(myKey)

  Dictionary is: Given value is: PT Associated key is: acronym

  Как получить ключ по значению с помощью list comprehension

  Для получения ключа, связанного с заданным значением, вместо метода index() можно использовать представление списка. О представлениях списков вы можете почитать в статье “List comprehensions и другие comprehensions в Python”.

  Чтобы найти ключ, мы создадим список ключей, значения которых равны заданному значению:

  myDict = print("Dictionary is:") print(myDict) dict_items = myDict.items() print("Given value is:") myValue = "PT" print(myValue) print("Associated key is:") myKey = Find key for value python print(myKey)

  Dictionary is: Given value is: PT Associated key is: ['acronym']

  Заключение

  В этой статье мы рассмотрели три способа получить из словаря Python ключ по значению: с помощью list comprehension , метода items() и метода index() .

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