Find Key by Value in Python Dictionary

Introduction

Dictionaries are a powerful data structure in Python that allow you to store key-value pairs. Sometimes, you may need to find the key associated with a particular value in a dictionary. In this challenge, you will write a function that takes a dictionary and a value as input, and returns the first key in the dictionary that has the given value.

Find the Key of a Value in a Dictionary

Write a function find_key(dict, val) that finds the first key in the provided dictionary that has the given value.

Your function should:

• Take a dictionary dict and a value val as input.
• Use dictionary.items() and next() to return the first key that has a value equal to val.
• Return the key as output.

def find_key(dict, val):
  return next(key for key, value in dict.items() if value == val)

ages = {
  'Peter': 10,
  'Isabel': 11,
  'Anna': 9,
}
find_key(ages, 11) ## 'Isabel'

Summary

In this challenge, you learned how to find the key associated with a particular value in a dictionary. You used the dictionary.items() method to iterate over the key-value pairs in the dictionary, and the next() function to return the first key that has a value equal to the input value.