Understanding some Python code

Question

I'm working my way through Gmail access using imaplib and came across:

# Count the unread emails
status, response = imap_server.status('INBOX', "(UNSEEN)")
unreadcount = int(response[0].split()[2].strip(').,]'))
print unreadcount

I just wish to know what:

status,

does in front of the "response =". I would google it, but I have no idea what I'd even ask to find an answer for that :(.

Thanks.

Answer 1

When a function returns a tuple, it can be read by more than one variable.

def ret_tup():
    return 1,2 # can also be written with parens

a,b = ret_tup()

a and b are now 1 and 2 respectively

Answer 2

See this page: http://docs.python.org/tutorial/datastructures.html

Section 5.3 mentions 'multiple assignment' aka 'sequence unpacking'

Basically, the function imap_server returns a tuple, and python allows a shortcut that allows you to initialize variables for each member of the tuple. You could have just as easily done

tuple = imap_server.status('INBOX', "(UNSEEN)")
status = tuple[0]
response = tuple[1]

So in the end, just a syntactic shortcut. You can do this with any sequence-like object on the right side of an assignment.

Answer 3

Though the answers given are certainly sufficient, an quick application of this python feature is the ease of swapping values.

In a normal language, to exchange the values of variables x and y, you would need a temporary variable

z = x
x = y
y = z

but in python, we can instead shorten this to

x, y = y, x