[Tutor] FW: find() problem
Evert Rol
evert.rol at gmail.com
Tue Aug 24 17:44:22 CEST 2010
> > > > > def find(strng, ch, start, step=1):
> > > > > index = start
> > > > The problem lies here, if you do a print on index, it never gets past
> > > > the first index of the number, so
> > > > your while loop below goes into an infinite loop.
> > > >
> > > > For example:
> > > > find('starfruit','t',0) <- First time will return 1
> > > > find('starfruit','t',1) <- Still returns 1. Infinite loop
> > > >
> > > > > while 0 <= index < len(strng):
> > > > > if strng[index] == ch:
> > > > > return index
> > > > > index += step
> > > > > return -1
Why are you returning -1 here?
-1 is a valid list index.
And with your last change, it makes your main condition valid.
> > > > >
> > > > > fruit=""
> > > > > letter=""
> > > > > fruit= raw_input("Enter a sort of fruit: ")
> > > > > letter = raw_input("Enter the character which must be counted: ")
> > > > > start=0
> > > > > aantal=0
> > > > > while 0 <=start < len(fruit):
> > > > > x=find (fruit,letter, start)
> > > > > aantal +=1
> > > > > start=x
> > > > > print "De letter", letter , "komt", aantal , "maal voor in het woord", fruit
> > > > >
> > > >
> > > > HTH,
> > > > Tino
> > >
> > > Hello,
> > >
> > > Your right. index get never past 1
> > > But in my opinion when something is found then x will be the place where the character is be found.
> > > After that the counter is increased and start gets the value of x.
> > > So start should change.
> > >
> > > Now finding out why this is not happening.
> >
> > You're including the previous found index; so it will just find the character at that same index again. You need to start the next search one index further down the word.
>
>
> Hello Evert.
>
> Stupid mistake.
> I change start=x to start=x+1
> But still it's not working properly.
>
> I can see that on this example.
>
> Fruit : banaan
> letter : a
>
> That a is being found at 2,4,5 which is correct but the programm don't end.
> So there's another error somewhere,
>
> Roelof
>
> >
> >
> > >
> > > But thanks for the help.
> > >
> > > Roelof
> > >
> > > _______________________________________________
> > > Tutor maillist - Tutor at python.org
> > > To unsubscribe or change subscription options:
> > > http://mail.python.org/mailman/listinfo/tutor
> >
>
> _______________________________________________
> Tutor maillist - Tutor at python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor
More information about the Tutor
mailing list