Question

So I have the code:

def logdata(x, y):
    try:
        f = open('multlog.txt', 'a')
        f.write("{0:g} * {1:g} = {2:g}\n".format(x,y, (x*y)))
    except ValueError:
        f.write("Error, you tried to multiply by something that wasn't a number")
        raise
    finally:
        f.close()
print("This is a test program, it logs data in a text file, 'multlog.txt'")
fn = input("Enter the first number you'd like to multiply by: ")
sn = input("Enter the second number you'd like to multiply by: ")
logdata(int(fn), int(sn))

And what I want it to do, is when it reaches a value error, for it to write to the file,”Error, you tried to multiply by something that wasn’t a number”. But, if the file reaches a value error if the user inputs a letter, say “j”,ValueError: invalid literal for int() with base 10: 'j', it doesn’t write to the file!

Answer 1

At least two problems:

1. The file is not open for writing (or appending) in the except block.
2. As @DSM points out in a comment, the ValueError is being raised when you call int()

I would rewrite to something like the below example.
If you use the with statement then you can do without the finally block.

def logdata(x, y):
    with open('multlog.txt', 'a') as f:
        try:
            x = int(x); y = int(y)
            f.write("{0:g} * {1:g} = {2:g}\n".format(x,y, (x*y)))
        except ValueError:
            f.write("Error")

print("This is a test program, it logs data in a text file, 'multlog.txt'")
fn = input("Enter the first number you'd like to multiply by: ")
sn = input("Enter the second number you'd like to multiply by: ")
logdata(fn, sn)