Python and "with" statement

Question

I have recently seen a "with" statement used like so:

with open("file.txt","r") as f:
f.read()

As much as i understand it... this shortcuts come part of method or variable.
So in my thinking way this should work:

list = [1,2,3]

with list as l:
print(l[1])

But it gives me error... So what is "with" statement used for?

Answer 1

with - specifically for OS BIOS it is used opening files

with open('txt.js','r') as f:
# with helps name the file to a variable f
lines = f.readlines ()
if lines == None:
pass
else:
print(lines)

Answer 2

and calling a variable list is forbidden as it is a reserved word :)

Answer 3

So i'm unable to get variables or methods like that but in shorter form?

Answer 4

Thanks :)