Question

I am parsing a csv file where the first line is the header.
I want to sum the amount column according to dates, but am getting an error message.
To debug I am checking if the column is a digit as well as if it is a string according to the error message – and it is both.
What could be the reason for this?

def parseDataFromFile(self,f):
    fh = open(f,'r')
    s = 0
    for line in fh:
        #parsing the line according to comma and stripping the '\n' char
        year,month,day,amount = line.strip('\n').split(',')

        #checking the header row, could check if was first row as well - would be faster
        if (amount == "Amount"): continue

        #just for the debug checks
        #here is the question

        if isinstance(amount,str):
            print "amount is a string"
            #continue
        if amount.isdigit:
            print "amount is a digit"

        #sum on the amount column
        s = s + amount

Output:
amount is a string
amount is a digit
amount is a string
amount is a digit

Error:

s = s + amount 
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Answer 1

Your problem is that s is an integer, you initialize it to 0. Then you try to add a string to it. amount is always a string. You do nothing to turn your number-like data into actual numbers, it will always be a string.

If you expect amount to be a number, then use:

s += float(amount)

PS: you should use the csv module in the stdlib for reading CSV files.