How to find key by value python

Python Dictionary Search by value

In this Python tutorial, we will study the implementation of Python Dictionary Search by value. Here we will see how to search for a value in Dictionary using some examples in python.

In Python, dictionaries are built-in data structure that stores key-value pairs. The keys in a dictionary must be unique, while the values can be of any data type.

There are a few different ways to get the key by value in a Python dictionary, depending on your specific use case.

• Using the items()method
• Using the list comprehension
• Using the index() method
• Using the filter() and lambda function

Method-1: Using the items() method

To get the key by value in a python dictionary is using the items() method and a for loop, items() method returns a view object that contains the key-value pairs of the dictionary, as tuples in a list.

# This code creates a dictionary called "countries" that contains the keys "USA", "Germany", and "France" # and the respective values 56, 25, and 78. countries = # The for loop iterates through the items in the dictionary, where "key" represents the key of each item # and "value" represents the value of each item. for key, value in countries.items(): # The if statement checks if the value of each item is equal to 56. if value == 56: # If the value is equal to 56, the key of that item is printed. print(key)

The above code outputs the USA as it is the key which has a value of 56.

Method 2: Using the list comprehension

This method iterates over the key-value pairs in the dictionary and uses a list comprehension to find the first key whose associated value is equal to the value you’re looking for.

# This code creates a dictionary called "my_dictionary" that contains keys and values # representing countries and their respective values. my_dictionary = # The variable new_val is set to 456 new_val = 456 # A list comprehension is used to iterate through the items in the dictionary and check if the value of each item is equal to new_val. # If the value is equal to new_val, the key of that item is added to the list. result=[new_k for new_k in my_dictionary.items() if new_k[1] == new_val][0][0] # The result is printed print(result) 

The code outputs “United Kingdom” as it is the key which have value 456.

Method-3: Using the index() method

The index() method is a built-in method in Python that is used to find the index of an element in a list. It takes a single argument, which is the element you want to find the index of and returns the index of the first occurrence of that element in the list.

# This code creates a dictionary called "my_dictionary" that contains keys and values # representing countries and their respective values. my_dictionary = # Get the values from the dictionary as a list values = list(my_dictionary.values()) # The variable new_val is set to 456 new_val = 456 # Find the index of the value in the list index = values.index(new_val) # Get the key from the dictionary using the index result = list(my_dictionary.keys())[index] # The result is printed print(result) 

The above code outputs “United Kingdom” as it is the key which has value 456 but uses the index() method of the list.

Method-4: Using the filter() and lambda function

The lambda function is a small anonymous function that can be used to perform a certain operation, and the filter() function is used to filter a sequence of elements based on a certain condition.

# my_dictionary is a dictionary that contains keys as countries and values as their population my_dictionary = # new_val is the population value for which we want to find the corresponding country new_val = 456 # Using lambda and filter() functions to filter the items of the dictionary # and only the items with the value of new_val are returned result = list(filter(lambda x: x[1] == new_val, my_dictionary.items()))[0][0] # The result is printed print(result)

The above code outputs “United Kingdom” as it is the key that has value 456 but uses the filter() and lambda function.

You may also like to read the following Python tutorials.

In this Python tutorial, we have covered how to get a key using the value of the dictionary by following the below methods.

• Python Dictionary Search by value using the items() method
• Python Dictionary Search by value using the list comprehension
• Python Dictionary Search by value using the index() method
• Python Dictionary Search by value using the filter() and lambda function

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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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.

  Источник