Python Programming Essentials - M13 - Tuples

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Python Tuples
Pavan Verma
@YinYangPavan
Python Programming Essentials

© SkillBrew http://skillbrew.com
What is a Tuple
 Tuple is a sequence of items, similar to a list
 The difference between list and tuple is:
tuple is immutable while list is mutable
2

Tuple example
 Lets say we want to represent number of
hits on blog on a particular date
3

Lets create a tuple
Myblog.com 100 20-Oct-2013
4
blog_hits = ['Myblog.com', 50, '20-Oct-2013']
blog_hits = ('Myblog.com', 50, '20-Oct-2013')
list
tuple

Packing a Tuple
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blog_hits = 'Myblog.com', 50, '20-Oct-2013'
print blog_hits
('Myblog.com', 50, '20-Oct-2013')

Unpacking a Tuple
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>> blog_name, hits, date = blog_hits
>> print blog_name, hits, date
'Myblog.com' 50 '20-Oct-2013'

Accessing Values in Tuples
Myblog.com 100 20-Oct-2013
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>>> blog_hits = ('Myblog.com', 50, '20-Oct-2013')
>>> blog_hits[0]
Myblog.com
>>> blog_hits[2]
20-Oct-2013
0 1 2

Tuple with a single element
>>> blog_hits = ('Myblog.com')
>>> type(blog_hits)
<type 'str'>
>>> blog_hits = ('Myblog.com', )
>>> type(blog_hits)
<type 'tuple'>
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Must have this comma

Common Operations on Tuples
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Python Expression Results Description
len(1, 2, 3) 3 Length
(1, 2, 3) + (4, 5, 6) (1, 2, 3, 4, 5, 6) Concatenation
a = (1, 2, 3, 4, 5, 6)
a[2:5]
(3, 4, 5) Slicing

How are Tuples different from Lists
 Apart from syntactical difference ( ) vs [ ], the real
difference is that lists are mutable whereas tuples
are not
 Tuples (generally) are sequences of different kinds
of stuff, and you deal with the tuple as a coherent
unit
 Lists (generally) are sequences of the same kind of
stuff, and you deal with the items individually
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Tuples are Immutable
>>> blog_hits[0] = 'yourblog.com'
Traceback (most recent call last):
File "<pyshell#3>", line 1, in <module>
blog_hits[0] = 'yourblog.com'
TypeError: 'tuple' object does not support item assignment
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Example of tuple and list usage
>>> colors = ['red', 'green', 'blue']
>>> colors = [
('red', '#FF0000'),
('green', '#00FF00'),
('blue', '#0000FF')
]
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• tuples are used in Python where a struct would be
used in C/C++
• Tuples usually heterogeneous data whereas lists
usually contain homogenous data

Converting a tuple to list
>>> blog_hits = ('Myblog.com', 50, '20-Oct-2013')
>>> list(blog_hits)
['Myblog.com', 50, '20-Oct-2013']
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Use list() function to convert
a tuple to a list

Use tuple to return multiple values from functions
Tuples are used to return multiple values from a function
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>>> def points(x):
y = 1 - x
return x, y
>>> points(.5)
(0.5, 0.5)
>>> t = points(.3)
>>> t
(0.3, 0.7)
>>> t[0]
0.3
>>> t[1]
0.7
>>>

Summary
 What is a tuple
 Packing/unpacking a tuple
 Accessing values in tuple
 Tuple with a single element
 Tuples are immutable
 How are tuples different form lists
 Converting between tuple and list
 Returning multiple values from functions
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References
 Tutorial on tuples
http://www.tutorialspoint.com/python/python_tuples.htm
 Basics tuple operation python documentation
http://docs.python.org/2/tutorial/datastructures.html#tuples-
and-sequences
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Python Programming Essentials - M13 - Tuples

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