[Tutor] help with exercise 15 of zed shaw's LPTHW

[lohecn at tuta.io]

hey everyone. this is my first time trying this -- actually, I've been 
studying python only for some days now, and I'm afraid my questions are going 
to be reeeeally simple, but I can't seem to understand this piece of code and 
thus can't move on.

you probably know the book, so you know that zed always makes us write code 
so that then we can understand how it works, and it's great, but in this 
exercise there are just too many new functions and without explanation they 
are a bit hard to understand... so I'm having trouble with most of the lines 
here.

it's not that I want the full explanation to that code, but since I'm 
unfamiliar with some of its concepts, I'm just going to tell you all the 
things that I don't understand (sorry for it being a lot):
1. the need to put script into an estipulation for argv (line 3)
2. the what is txt and why it has to be used there (line 4)
3. txt.read() -- which are all new functions(? I dont even know what they 
are)  (line 7)
4. file_again (line 10)
5. txt_again (line 12)
and line 14.

as you can see, it's pretty much everything. sorry about that.
I'd really appreciate any help at all!
thanks a lot,

heloisa