Tuple

Tuple

What is Tuple?

                A tuple is a sequence of immutable Python objects. Tuples are sequences, just like lists. The only difference is that tuples can't be changed ie. tuples are immutable and tuples use parentheses and lists use square brackets.

Creating a tuple is as simple as putting different comma-separated values and optionally you can put these comma-separated values between parentheses also. For example:

tup1 = ('physics', 'chemistry', 1997, 2000);

tup2 = (1, 2, 3, 4, 5 );

tup3 = "a", "b", "c", "d";

           Tuples are pretty easy to make. You give your tuple a name, then after that the list of values it will carry. For example, the months of the year:

Code Example 1 - creating a tuple

months = ('January','February','March','April','May','June',\

'July','August','September','October','November','  December')

Ø  Note that the '\' thingy at the end of the first line carries over that line of code to the next line. It is useful way of making big lines more readable.

Ø  Technically, you don't have to put those parentheses there (the '(' and ')' thingies), but it stops Python from getting things confused.

Ø   You may have spaces after the commas if you feel it necessary - it doesn't really matter.

                Python then organises those values in a handy, numbered index - starting from zero, in the order that you entered them in. It would be organised like this:

Table 1 - tuple indicies
Index	Value
0	January
1	February
2	March
3	April
4	May
5	June
6	July
7	August
8	September
9	October
10	November
11	December

Basic Tuples Operations:

                Tuples respond to the + and * operators much like strings; they mean concatenation and repetition here too, except that the result is a new tuple, not a string.

                In fact, tuples respond to all of the general sequence operations we used on strings in the prior chapter :

Python Expression	Results	Description
len((1, 2, 3))	3	Length
(1, 2, 3) + (4, 5, 6)	(1, 2, 3, 4, 5, 6)	Concatenation
['Hi!'] * 4	('Hi!', 'Hi!', 'Hi!', 'Hi!')	Repetition
3 in (1, 2, 3)	True	Membership
for x in (1, 2, 3): print x,	1 2 3	Iteration

 

Indexing, Slicing, and Matrixes:

                Because tuples are sequences, indexing and slicing work the same way for tuples as they do for strings. Assuming following input:

L = ('spam', 'Spam', 'SPAM!')

Python Expression	Results	Description
L[2]	'SPAM!'	Offsets start at zero
L[-2]	'Spam'	Negative: count from the right
L[1:]	['Spam', 'SPAM!']	Slicing fetches sections

 

No Enclosing Delimiters:

Any set of multiple objects, comma-separated, written without identifying symbols, i.e., brackets for lists, parentheses for tuples, etc., default to tuples, as indicated in these short examples:

#!/usr/bin/python

print 'abc', -4.24e93, 18+6.6j, 'xyz';

x, y = 1, 2;

print "Value of x , y : ", x,y;

When the above code is executed, it produces following result:

abc -4.24e+93 (18+6.6j) xyz

Value of x , y : 1 2

 

Built-in Tuple Functions:

Python includes following tuple functions

SN	Function with Description
1	cmp(tuple1, tuple2) Compares elements of both tuples.
2	len(tuple) Gives the total length of the tuple.
3	max(tuple) Returns item from the tuple with max value.
4	min(tuple) Returns item from the tuple with min value.
5	tuple(seq) Converts a list into tuple.