[Tutor] Re: parsing woes

[Vicki Stanfield]

> Okay, I didn't get an answer to this last time, so let me restate it and
> try again. I am attempting to parse a string which is in the form:
>
> 1 F 5
>
> I need to make parameter[0]= 1, parameter[1] = F, and parameter[2] = 5.
> The difficulty is that there might be no parameters or any number up to 3.
> They won't always be a single digit or letter but they will always be
> space-delimited. My problem is that when I try to display them, I get an
> error if there are not 3 parameters.
>
>     if parameters[2]:
> IndexError: list index out of range
>
> when I try to run this code to see what the values are:
>     if parameters[0]:
>          print parameters[0]
>     if parameters[1]:
>          print parameters[1]
>     if parameters[2]:
>          print parameters[2]
>
> I am parsing them this way:
>
> if arguments:
>     parameters=arguments.split(" ")
> else: parameters = ""
>
>
> Can someone tell me what I am doing wrong? I just want the if
> parameters[2] to be bypassed if there isn't a third parameter.
>
> --vicki
>
>
Okay I finally got it figured out. I had to change the if statements to
try statements and deal with the index error. The code looks like this
now:

            if arguments:
                parameters=arguments.split(" ")
                i=0
                for a in parameters:
                    print "parameter[" + str(i) + "] = " + a + "\n"
                    i+=1

and then:

            try:
                parameters[0]
            except IndexError:
                print "parameters[0] undefined"
            else:
                print parameters[0]
            try:
                parameters[1]
            except IndexError:
                print "parameters[1] undefined"
            else:
                print parameters[1]
            try:
                parameters[2]
            except IndexError:
                print "parameters[2] undefined"
            else:
                print parameters[2]

--vicki