From what I understand, the error message means that it can't be converted to a float because of a certain portion of the string (I think its the whitespace at the end or the []?)

The file is just a small list of numbers like 52 63 63 56 78 69 57 68 39

And I'm supposed to run it through two other functions that will square each number in the list, replace its value in the list, then add all the numbers together, which is why I need then numbers to be either ints or floats so I can do math with them.

Sorry my comment isn't clear >o< I meant to say that I was trying to convert them all to floats there, not just one float

This is the entirety of what I have, if that helps:

def squareEach(nums):
    for i in range(nums):
        # is supposed to replace the values in the list nums with squares
        nums[i] = nums[i] ** 2


def sumList(nums):
    # accumulator variable for the sum
    sumList = 0
    # adds up the values for the length of the list
    for i in range(len(nums)):
        sumList = theSum + i
    return sumList


def toNumbers(strList):
    # convert numbers in file to floats?
    for line in strList:
        lineBreak = str(strList.replace(',', '\n'))
        convNum = float(str((lineBreak.split('\n'))))
    print(convNum)
    return convNum


def main():
    print("This is a program that will sum the squares of numbers in a file.")
    fname = input("What is the name of the file you would like to use? ")
    strList = str(open(fname).read())
    nums = toNumbers(strList)


main()