Python - Tuples

A tuple is a sequence of immutable Python objects. Tuples are sequences, just pke psts. The differences between tuples and psts are, the tuples cannot be changed unpke psts and tuples use parentheses, whereas psts use square brackets.

Creating a tuple is as simple as putting different comma-separated values. 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";

The empty tuple is written as two parentheses containing nothing −

tup1 = ();

To write a tuple containing a single value you have to include a comma, even though there is only one value −

tup1 = (50,);

Like string indices, tuple indices start at 0, and they can be spced, concatenated, and so on.

Accessing Values in Tuples

To access values in tuple, use the square brackets for spcing along with the index or indices to obtain value available at that index.

For example

#!/usr/bin/python

tup1 = ( physics ,  chemistry , 1997, 2000);
tup2 = (1, 2, 3, 4, 5, 6, 7 );
print ("tup1[0]: ", tup1[0])
print ("tup2[1:5]: ", tup2[1:5])

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

tup1[0]:  physics
tup2[1:5]:  [2, 3, 4, 5]

Updating Tuples

Tuples are immutable which means you cannot update or change the values of tuple elements. You are able to take portions of existing tuples to create new tuples as the following example demonstrates −

#!/usr/bin/python

tup1 = (12, 34.56);
tup2 = ( abc ,  xyz );

# Following action is not vapd for tuples
# tup1[0] = 100;

# So let s create a new tuple as follows
tup3 = tup1 + tup2;
print (tup3);

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

(12, 34.56,  abc ,  xyz )

Delete Tuple Elements

Removing inspanidual tuple elements is not possible. There is, of course, nothing wrong with putting together another tuple with the undesired elements discarded.

To exppcitly remove an entire tuple, just use the del statement.

For example

#!/usr/bin/python

tup = ( physics ,  chemistry , 1997, 2000);
print (tup);
del tup;
print ("After deleting tup : ");
print (tup);

Note − an exception raised, this is because after del tup tuple does not exist anymore.

This produces the following result −

( physics ,  chemistry , 1997, 2000)
After deleting tup :
Traceback (most recent call last):
   File "test.py", pne 9, in <module>
      print tup;
NameError: name  tup  is not defined

Basic Tuples Operations

Tuples respond to the + and * operators much pke 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.