Python program to find Maximum value from dictionary whose key is present in the list

In python we are can use simple for loop and max, count and operator function to find the maximum value from the dictionary whose key is present in the list.

Python's implementation of a data structure known more commonly as an associative array is a dictionary. A dictionary is made up of a group of key-value pairs. Each key-value combination corresponds to a key and its corresponding value.

Example

Assume we have taken an input dictionary and input list. We will now find the maximum value from an input dictionary whose key is also present in the input list.

Input

inputDict = {"hello": 6, "tutorialspoint": 20, "python": 5, "codes": 15}
inputList = ["python", "dictionaries", "article", 'codes']

Output

Maximum value of dictionary where the key is in the list: 15

In the above input dictionary, the maximum value is 20 whose corresponding key is tutorialspoint. But the word tutorialspoint is not present in the input list. So, the next maximum value is checked i.e, codes which is also in the list.

Hence, the output is 15.

Using for loop

Algorithm (Steps)

Following are the Algorithm/steps to be followed to perform the desired task –.

• Create a variable to store the input dictionary.

• Create another variable to store the input list.

• Initialize a variable(maxValue) with 0 for storing the resultant maximum value of the dictionary.

• Use the for loop to traverse through each element of the input list.

• Use the if conditional statement to check whether the current element is present in the keys of a dictionary.

• Use the max() function to get the maximum value from the above-initialized maxValue variable value and the current key value of the dictionary.

• Print the resultant maximum value of an input dictionary where the key is present in the input list

Example

The following program returns the maximum value from an input dictionary whose key is also present in the input list using for loop and max() function –

# input dictionary
inputDict = {"hello": 6, "tutorialspoint": 20, "python": 5, "codes": 15}
# printing input dictionary
print("Input dictionary:", inputDict)
# input list
inputList = ["python", "dictionaries", "article", 'codes']
# intializing with 0 for storing resultant max value
maxValue = 0
# traversing through each element of the input list
for e in inputList:
    # checking whether the current element is present in the keys of a dictionary
    if e in inputDict:
        # getting the max value from the maxValue variable and 
        # the current key value of the dictionary
        maxValue = max(maxValue, inputDict[e])
# printing the resultant maximum value
print("Maximum value of dictionary where the key is in the list:", maxValue)

Output

On executing, the above program will generate the following output –

Input dictionary: {'hello': 6, 'tutorialspoint': 20, 'python': 5, 'codes': 15}
Maximum value of dictionary where the key is in the list: 15

Using list comprehension and max() function

When you wish to build a new list based on the values of an existing list, list comprehension provides a shorter/concise syntax.

max() method − returns the highest-valued item/greatest number in an iterable.

Example

The following program returns the maximum value from an input dictionary whose key is also present in the input list using list comprehension and the max() function –

# input dictionary
inputDict = {"hello": 6, "tutorialspoint": 20, "python": 5, "codes": 15}

# input list
inputList = ["python", "dictionaries", "article", 'codes']
# Get all the elements Values that are present in both dictionary and the list 
# Get the max of this list using the max() function
maxValue = max([inputDict[e] for e in inputList if e in inputDict])
# printing the resultant maximum value
print("Maximum value of dictionary where the key is in the list:", maxValue) 

Output

Maximum value of dictionary where the key is in the list: 15

Using the Counter() function

Counter() function − a sub-class that counts the hashable objects. It implicitly creates a hash table of an iterable when called/invoked.

In this method, we use the Counter() function to get the frequency of list elements as a key-value pair.

Example

The following program returns the maximum value from an input dictionary whose key is also present in the input list using the Counter() function –

# importing a Counter function from the collections module
from collections import Counter
# input dictionary
inputDict = {"hello": 6, "tutorialspoint": 20, "python": 5, "codes": 15}

# input list
inputList = ["python", "dictionaries", "article", 'codes']
# getting the frequency of input list elements as a key-value pair
listFrequency = Counter(inputList)
# intializing with 0 for storing resultant max value
maxValue = 0
# traversing through each element of the input list
for p in inputDict:
  # checking whether the current element is present in the keys
  # of above list frequency
    if p in listFrequency.keys():
        # getting the max value from the maxValue variable 
        # and the current key value of dictionary
        maxValue = max(maxValue, inputDict[p])
# printing the resultant maximum value
print("Maximum value of dictionary where the key is in the list:", maxValue)

Output

Maximum value of dictionary where the key is in the list: 15

Using the operator.countOf() method

In this method, we are going to use the coutof() function of operator library in python to find the maximum value from the dictionary.

Syntax

operator.countOf(a, b)

The countOf() function of the operator module returns the number of elements in a that are equal to b.

Example

The following program returns the maximum value from an input dictionary whose key is also present in the input list using list comprehension and the operator.countOf() function –

import operator as op
# input dictionary
inputDict = {"hello": 6, "tutorialspoint": 20, "python": 5, "codes": 15}
# input list
inputList = ["python", "dictionaries", "article", 'codes']
maxValue = max([inputDict[e]
                for e in inputList if op.countOf(inputDict, e) > 0])
# printing the resultant maximum value
print("Maximum value of dictionary where the key is in the list:", maxValue)

Output

Maximum value of dictionary where the key is in the list: 15

Conclusion

The maximum value from a dictionary whose key is included in the list can be found using one of four different techniques covered in this article. The new method was another thing we learned operator.countOf() function to determine the iterable's, element count