Author Dusty Phillips Reviewers

>>> stock = "FB", 75.00, 75.03, 74.90
>>> stock2 = ("FB", 75.00, 75.03, 74.90)
If we're grouping a tuple inside of some other object, such as a function call, list 
comprehension, or generator, the parentheses are required. Otherwise, it would 
be impossible for the interpreter to know whether it is a tuple or the next function 
parameter. For example, the following function accepts a tuple and a date, and returns 
a tuple of the date and the middle value between the stock's high and low value:
import datetime
def middle(stock, date):
symbol, current, high, low = stock
return (((high + low) / 2), date)
mid_value, date = middle(("FB", 75.00, 75.03, 74.90),
datetime.date(2014, 10, 31))
The tuple is created directly inside the function call by separating the values with 
commas and enclosing the entire tuple in parenthesis. This tuple is then followed
by a comma to separate it from the second argument.
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Python Data Structures
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This example also illustrates tuple unpacking. The first line inside the function 
unpacks the 
stock
parameter into four different variables. The tuple has to be 
exactly the same length as the number of variables, or it will raise an exception. We 
can also see an example of tuple unpacking on the last line, where the tuple returned 
inside the function is unpacked into two values, 
mid_value
and 
date
. Granted, this 
is a strange thing to do, since we supplied the date to the function in the first place, 
but it gave us a chance to see unpacking at work.
Unpacking is a very useful feature in Python. We can group variables together to 
make storing and passing them around simpler, but the moment we need to access 
all of them, we can unpack them into separate variables. Of course, sometimes we 
only need access to one of the variables in the tuple. We can use the same syntax 
that we use for other sequence types (lists and strings, for example) to access an 
individual value: