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tuple


A tuple is another sequence data type that is similar to the list. A tuple consists of a number of values separated by commas. Unlike lists, however, tuples are enclosed within parentheses.
The main differences between lists and tuples are: Lists are enclosed in brackets ( [ ] ) and their elements and size can be changed, while tuples are enclosed in parentheses ( ( ) ) and cannot be updated. Tuples can be thought of as read-only lists.

For example − 
tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 )
tinytuple = (123, 'john')
 
print tuple # Prints complete list
print tuple[0] # Prints first element of the list
print tuple[1:3] # Prints elements starting from 2nd till 3rd
print tuple[2:] # Prints elements starting from 3rd element
print tinytuple * 2 # Prints list two times
print tuple + tinytuple # Prints concatenated lists
 
This produce the following result −
('abcd', 786, 2.23, 'john', 70.200000000000003)
abcd
(786, 2.23)
(2.23, 'john', 70.200000000000003)
(123, 'john', 123, 'john')
('abcd', 786, 2.23, 'john', 70.200000000000003, 123, 'john')
 
The following code is invalid with tuple, because we attempted to update a tuple, which is not allowed. Similar case is possible with lists −
tuple = ( 'abcd', 786 , 2.23, 'john', 70.2 )
list = [ 'abcd', 786 , 2.23, 'john', 70.2 ]
tuple[2] = 1000 # Invalid syntax with tuple
list[2] = 1000 # Valid syntax with list


 

Accessing Values in Tuples

To access values in tuple, use the square brackets for slicing along with the index or indices to obtain value available at that index. For example −
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 −
tup1 = (12, 34.56);
tup2 = ('abc', 'xyz');
# Following action is not valid 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 individual tuple elements is not possible. There is, of course, nothing wrong with putting together another tuple with the undesired elements discarded.
To explicitly remove an entire tuple, just use the del statement. For example:
tup = ('physics', 'chemistry', 1997, 2000);
print tup
del tup;
print "After deleting tup : "
print tup
 
This produces the following result. Note an exception raised, this is because after del tup tuple does not exist any more −
('physics', 'chemistry', 1997, 2000)
After deleting tup :
Traceback (most recent call last):
File "test.py", line 9, in <module>
print tup;
NameError: name 'tup' is not defined

 

 

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 −
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 the following result −
abc -4.24e+93 (18+6.6j) xyz
Value of x , y : 1 2

 

 

Built-in Tuple Functions

Function with Description

cmp(tuple1, tuple2)

Compares elements of both tuples.

len(tuple)

Gives the total length of the tuple.

max(tuple)

Returns item from the tuple with max value.

min(tuple)

Returns item from the tuple with min value.

tuple(seq)

Converts a list into tuple.

 

 

 

 
         
 
 
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