Python program to find the sum of dictionary keys

In this article, we will learn different Python methods to find the sum of dictionary keys. Python provides several built-in functions that make this task efficient and straightforward.

Methods Overview

The following are the various methods to accomplish this task ?

• Using for loop

• Using dict.keys() and sum() functions

• Using reduce() function

• Using items() function

Example Input and Expected Output

Assume we have an input dictionary containing numeric keys. We will find the sum of all the keys using different methods ?

Input

inputDict = {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}

Output

Sum of keys of an input dictionary: 25

In the above example, the sum of keys is 4+1+10+2+8 = 25.

Method 1: Using For Loop

The most straightforward approach is to iterate through all keys using a for loop and accumulate their sum ?

# input dictionary
inputDict = {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}

# printing the input dictionary
print("Input Dictionary:", inputDict)

# storing the sum of keys of the input dictionary
keysSum = 0

# traversing through the keys of an input dictionary
for k in inputDict:
    # adding the current key to keysSum variable
    keysSum += k

# printing the sum of keys of an input dictionary
print("Sum of keys of an input dictionary:", keysSum)

Input Dictionary: {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
Sum of keys of an input dictionary: 25

Method 2: Using dict.keys() and sum() Functions

The dict.keys() function returns a view object containing all dictionary keys. We can pass this directly to sum() function for a more concise solution ?

# input dictionary
inputDict = {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
print("Input Dictionary:", inputDict)

# getting the sum of dictionary keys directly
keysSum = sum(inputDict.keys())
print("Sum of keys of an input dictionary:", keysSum)

Input Dictionary: {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
Sum of keys of an input dictionary: 25

Method 3: Using reduce() Function

The reduce() function from the functools module applies a function cumulatively to items in an iterable. We can use it with a lambda function to sum all keys ?

# importing reduce function from functools module
from functools import reduce

inputDict = {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
print("Input Dictionary:", inputDict)

# Add the keys and reduce it to a single number(sum) using reduce() function
keysSum = reduce(lambda p, q: p + q, inputDict)
print("Sum of keys of an input dictionary:", keysSum)

Input Dictionary: {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
Sum of keys of an input dictionary: 25

Method 4: Using items() Function

The items() function returns key-value pairs as tuples. We can iterate through these tuples and sum only the keys ?

inputDict = {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
print("Input Dictionary:", inputDict)

# storing the sum of keys of the input dictionary
keysSum = 0

# traversing through the keys and values of an input dictionary
for key, value in inputDict.items():
    # adding the current key to keysSum variable
    keysSum += key

print("Sum of keys of an input dictionary:", keysSum)

Input Dictionary: {4: 10, 1: 30, 10: 50, 2: 70, 8: 90}
Sum of keys of an input dictionary: 25

Comparison of Methods

Conclusion

The most efficient and readable approach is using sum(inputDict.keys()). Use the for loop method when you need additional processing logic, and consider reduce() for functional programming patterns.