dbushenko/python.org

## python.org

      
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    Python programming exampleh

Org-mode formatting utilities

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My email: d.bushenko@gmail.com
02.09.2013

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This link will point to org-mode home site: http://orgmode.org
http://orgmode.org
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. Following is a simple 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 them or change values of tuple elements. But we able to take portions of an existing tuples to create a new tuples as follows. Following is a simple example:
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. Following is a simple example:
tup = ('physics', 'chemistry', 1997, 2000);

print tup;
del tup;
print "After deleting tup : "
print tup;
This will produce 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
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