python int( ) function

Question

The code below shows error if a decimal (eg. 49.9) is sent to next variable. Can you please tell me why? Why does int() converts it into an in

Answer 1

As the other answers have mentioned, the int operation will crash if the string input is not convertible to an int (such as a float or characters). What you can do is use a little helper method to try and interpret the string for you:

def interpret_string(s):
    if not isinstance(s, basestring):
        return str(s)
    if s.isdigit():
        return int(s)
    try:
        return float(s)
    except ValueError:
        return s

So it will take a string and try to convert it to int, then float, and otherwise return string. This is more just a general example of looking at the convertible types. It would be an error for your value to come back out of that function still being a string, which you would then want to report to the user and ask for new input.

Maybe a variation that returns None if its neither float nor int:

def interpret_string(s):
    if not isinstance(s, basestring):
        return None
    if s.isdigit():
        return int(s)
    try:
        return float(s)
    except ValueError:
        return None

val=raw_input("> ")
how_much=interpret_string(val)
if how_much is None:
    # ask for more input? Error?