I am trying to implement a function in Python that will take a list of integers as an input and retu-CodePudding

"I am trying to implement a function in Python that will take a list of integers as an input and return the sum of all the even numbers in the list. I have written the following code, but it is giving me an error when I try to run it.

def sum_evens(numbers):
    result = 0
    for num in numbers:
        if num % 2 == 0:
            result  = num
    return result

print(sum_evens([1, 2, 3, 4, 5]))

The error message I am getting is: 'TypeError: unsupported operand type(s) for =: 'int' and 'str'.

Can someone please help me understand why this error is occurring and how I can fix it?"

CodePudding user response：

Your code works fine on my computer. However, guessing by your error message, num must be a string. You can fix this by converting it to an integer beforehand:

def sum_evens(numbers):
    result = 0
    for num in numbers:
        # convert to integer
        num = int(num)

        if num % 2 == 0:
            result  = num
    return result

CodePudding user response：

This error is occurring because you are attempting to add a string ('str') to an integer ('int'). This is not allowed in Python, and so the interpreter raises a TypeError to indicate that the operation is not supported.

The most likely cause of this error is that one or more of the elements in the numbers list are strings, rather than integers. For example, if the list contains the elements ['1', '2', '3', '4', '5'] instead of [1, 2, 3, 4, 5], the function will try to add the string '2' to the integer 0, which will cause the TypeError to be raised.

To fix this error, you will need to make sure that all the elements in the numbers list are integers, rather than strings. You can do this by using the int() function to convert any string elements to integers before trying to add them to the result variable.

Here is an example of how you could modify the code to handle this issue:

def sum_evens(numbers):
    result = 0
    for num in numbers:
        if num % 2 == 0:
            result  = int(num)
    return result

print(sum_evens([1, 2, 3, 4, 5]))

With this change, the function will first convert any string elements to integers before adding them to the result variable, which should allow the code to run without raising a TypeError.

CodePudding user response：

Another alternative using the list comprehension concept (functional paradigm):

def sum_events(numbers):
  return sum(num for num in numbers if int(num) % 2 == 0)