[Tutor] Program Problems

[Magnus Lyckå]

At 02:40 2004-07-16 +0000, mandy bowen wrote:
>If you see a problem, can you tell me?
>
>http://rafb.net/paste/results/88yf5V76.html
>
>I cannot figure out the errors.

The syntax error on the print statement at

         if option == 1:
             Account.deposit(input("Deposit amount:$")
             print "TRANSACTION COMPLETED"

is because you lack a ")" on the previous line. A logical
line in Python extends through several physical lines in
Python while you are inside {}, [] or (), so that you can
write things like:

def func(parameter1, parameter2, parameter3, parameter4,
          parameter5, parameter6, parameter7, parameter8,
          parameter9, parameter10, parameter11, parameter12):

This means that *your* code is interpreted as

         if option == 1:
             Account.deposit(input("Deposit amount:$") print "TRANSACTION 
COMPLETED" [...rest of program]

Of course, you can't have a print statement inside the method
call to Account.deposit().

It's very common that errors found by interpreters and
compilers are actually caused by something on the line above.
Python can't start complaining about the line where you
forgot the ), since it's correct to write your code like that.

A "smarter" compiler could have see that there aren't matching
) in the rest of the file, and given a proper diagnostic
message for that, but the current approach of going through the
code linearly and stopping at the first encountered error, has
some advantages from a debugging point of view, and it's probably
much easier to maintain the code and to keep the performance up
with this simple approach.

Of course, the error message could hint about the possibility
of this problem, but this is such a common thing that most
programmers (in all languages I've coded in) will check for
a thing like that on reflex when they see an error message like
that. The fact that it complained about something else when
you removed the print statements must in hindsight be seen as
a hint that your problem was actually somewhat earlier in the
code, but I've certainly been confused about that kind of error
myself in some long forgotten past. (Probably while coding
Pascal.)

>  Or this list.

Are you saying that you can't figure out the list or that the
list can't figure out the errors? ;)


--
Magnus Lycka (It's really Lyckå), magnus at thinkware.se
Thinkware AB, Sweden, www.thinkware.se
I code Python ~ The Agile Programming Language