Declaration of an array of unspecified size

[Ulrich Petri]

"Bertel Lund Hansen" <nospamius at lundhansen.dk> schrieb im Newsbeitrag
news:m814lvc8h44vbd5g1m2iv05r33qg8ag9ta at news.stofanet.dk...
> Hi all
>
> I am relatively new to Python but have som programming
> experience. I am experimenting wit a POP3-program and it's fairly
> easy.
>
> I want to read the mails into an array of lists so I later can
> choose which one to display. But I need to declare an array of
> unknown size before I can use it in the code. How do I manage
> that?

You don't. Python doesn't have the concept of declaring variables.

>
> class PopMailServer:
>   host = ""
>   user = ""
>   password = "*"
>   mails = 0
>   mail[] # This is wrong but what do I do?
mail = [] #would work

But you are creating class-variables here. Are you sure thats what you want?

>   def __init__ (self):
>     pop=poplib.POP3(self.host)
>     pop.user(self.user)
>     pop.pass_(self.password)
>     self.mails=len(pop.list()[1])
>     for i in range(self.mails):
>       self.mail[i]=pop.retr(i+1)[1] # This is also wrong.
>     pop.quit()
>     print "Antal mails: %d\n" % self.mails

you can skip the "mails" variable. len(mail) will give the same.

An optimzed (untested) version:

class PopMailServer:
    def __init__(self, host, user, pass):
        self.host = host
        self.user = user
        self.password = pass
        self.mail = []

    def action(self):
        pop = poplib.POP3(self.host)
        pop.user(self.user)
        pop.pass_(self.password)
        for x in p.list()[1]:
            num, len = x.split()
            self.mail.append(pop.retr(num)[1])
        pop.quit()
        print "Total mails: %d" % len(self.mail)

of course this lacks exception handling...

HTH

Ciao Ulrich