Add only numeric values present in a list in Python

We have a Python list which contains both strings and numbers. In this article we will see how to sum up the numbers present in such list by ignoring the strings.

Using filter() and isinstance()

The isinstance() function can be used to filter out only the numbers from the elements in the list. Then we apply the sum() function to get the final result.

Example

mixed_data = [1, 14, 'Mon', 'Tue', 23, 'Wed', 14, -4]

# Given list
print("Given list:", mixed_data)

# Add the numeric values using filter
result = sum(filter(lambda i: isinstance(i, int), mixed_data))
print("Sum of numbers in mixed_data:", result)

The output of the above code is −

Given list: [1, 14, 'Mon', 'Tue', 23, 'Wed', 14, -4]
Sum of numbers in mixed_data: 48

Using List Comprehension

This approach uses list comprehension with the isinstance() condition to filter numeric values, then applies the sum() function ?

Example

mixed_data = [1, 14, 'Mon', 'Tue', 23, 'Wed', 14, -4]

# Given list
print("Given list:", mixed_data)

# Add the numeric values using list comprehension
result = sum([x for x in mixed_data if isinstance(x, int)])
print("Sum of numbers in mixed_data:", result)

The output of the above code is −

Given list: [1, 14, 'Mon', 'Tue', 23, 'Wed', 14, -4]
Sum of numbers in mixed_data: 48

Using try-except Block

Another approach is to use exception handling to catch non-numeric values and skip them ?

Example

mixed_data = [1, 14, 'Mon', 'Tue', 23, 'Wed', 14, -4]

# Given list
print("Given list:", mixed_data)

# Add the numeric values using try-except
total = 0
for item in mixed_data:
    try:
        total += item
    except TypeError:
        pass  # Skip non-numeric values

print("Sum of numbers in mixed_data:", total)

The output of the above code is −

Given list: [1, 14, 'Mon', 'Tue', 23, 'Wed', 14, -4]
Sum of numbers in mixed_data: 48

Comparison

Conclusion

List comprehension with isinstance() is the most Pythonic approach for summing numeric values in mixed lists. Use filter() for functional programming style or try-except when dealing with complex data types.