prices = {'milk': 1.00, 'wine': 2.50, 'apples': 0.6}

def sum_bill(purchase):
    """Calculate the total amount to pay"""
    total = 0
    for item, quantity in purchase:
        total += prices[item]*quantity
    return total

#Testing the code
if __name__=='__main__':
    my_purchase = [('milk', 2), ('wine', 1),
                   ('apples', 1.2)]
    bill = sum_bill(my_purchase)

    print 'I owe %.2f Euros' % bill

>>> a = 1 #integer
>>> b = 1.2 #floating point
>>> c = "test" #string

>>> a + 2
3
>>> a + c
Traceback (most recent call last):
   ...
TypeError: unsupported operand type(s) for +: 'int' and 'str'

>>> a = []                 #an empty list
>>> b = ['eggs', 'butter'] #list of strings
>>> c = ['eggs', 4, []]    #mixed-type lists

>>> c[0]                   #get first element
'eggs'

>>> c[3]
Traceback (most recent call last):
    ...
IndexError: list index out of range

>>> c[2] = 3               #modify 3rd element

>>> c.append('flower')     #add an element
>>> c
['eggs', 4, 3, 'flower']

>>> del c[0]               #remove an elemeni
>>> c
[4, 3, 'flower']

>>> c + ['new', 'list']                #concatenate lists
[4, 3, 'flower', 'new', 'list']

>>> d = [1, 2, 3, 4, 5, 6]
>>> d[1:3]
[2, 3]
>>> d[:3]
[1, 2, 3]
>>> d[1::2]
[2, 4, 6]

>>> d[-1]
6
>>> d[2:-2]
[3, 4]

>>> tup = ('a', 'b', 3)
>>> tup[1]
'b'

>>> tup[2]=5
Traceback (most recent call last):
  ...
TypeError: 'tuple' object does not support item assignment

>>> x, y, z = tup
>>> print x, y, z
a b 3

>>> x, y = (3, 4)
>>> temp = x
>>> x = y
>>> y = temp
>>> print x, y
4 3

>>> x, y = (3, 4)
>>> y, x = x, y
>>> print x, y
4 3

>>> tel = {'jack': 4098, 'sape': 4139}

>>> tel['sape']
4139

>>> tel['jack'] = 4100
>>> tel['guido'] = 4127
>>> tel
{'sape': 4139, 'jack': 4100, 'guido': 4127}

if n==1:
    print "Winner!"
elif n==2:
    print "First runner-up"
elif n==3:
    print "Second runner-up"
else:
    print "Work hard next time!"

comments = {1: "Winner!",
            2: "First runner-up.",
            3: "Second runner-up."
            }

print comments.get(n, "Work hard next time!")

>>> str1 = '"Hello", she said.'
>>> str2 = "'Hi', he replied."
>>> print str1, str2
"Hello", she said. 'Hi', he replied.

>>> str3 = """'Hello', she said.
... 'Hi', he replied."""
>>> print str3
'Hello', she said.
'Hi', he replied.

>>> str1[1]
'H'
>>> str1[1:6]
'Hello'

>>> a = 'Hello' + 'world'
>>> print a
Helloworld

>>> colors = ['red', 'blue', 'yellow', 'green']
>>> print ''.join(colors)
redblueyellowgreen

>>> print ' '.join(colors)
red blue yellow green

>>> name, messages = "Bartosz", 2
>>> text = ('Hello %s, you have %d messages.' % (name, messages))
>>> print text
Hello Bartosz, you have 2 messages.

>>> print 'Real number with 2 digits after point %.2f' % (2/3.)
Real number with 2 digits after point 0.67
>>> print 'Integer padded with zeros %04d' % -1
Integer padded with zeros -001

>>> entry = "%(name)s's phone number is %(phone)d"
>>> print entry % {'name': 'guido', 'phone': 4343}
guido's phone number is 4343

>>> type([])
<type 'list'>
>>> dir([])
['__add__', '__class__', '__contains__', '__delattr__', '__delitem__', '__delslice__', '__doc__', '__eq__', '__ge__', '__getattribute__', '__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__', '__setattr__', '__setitem__', '__setslice__', '__str__', 'append', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']

>>> n = -4
>>> if n > 0:
...     print 'greater than 0'
... elif n==0:
...     print 'equal to 0'
... else:
...     print 'less than 0'
less than 0

x = true_value if condition else false_value

>>> abs_n = -1*n if n<0 else n
>>> abs_n
4

>>> items = ['ala', 'ma', 'kota']
>>> if items:
...     print 'ala has a cat'
... else:
...     print 'list is empty'
ala has a cat

>>> num_moons = 3
>>> while num_moons > 0:
...    print num_moons,
...    num_moons -= 1
3 2 1

>>> for i in xrange(3):
...    print i,
0 1 2

>>> clock = ['tic', 'tac', 'toe']
>>> for x in clock:
...     print x,
tic tac toe

>>> prices = {'apples': 1, 'grapes': 3}
>>> for key, value in prices.iteritems():
...     print '%s cost %d euro per kilo' % (key, value)
apples cost 1 euro per kilo
grapes cost 3 euro per kilo

>>> for i, x in enumerate(clock):
...     print i, x,
0 tic 1 tac 2 toe

>>> [x**2 for x in xrange(5)]
[0, 1, 4, 9, 16]

>>> freshfruit = ['  banana',
...               '  loganberry ',
...              'passion fruit  ']
>>> [x.strip() for x in freshfruit]
['banana', 'loganberry', 'passion fruit']

>>> [[i*j for i in xrange(1,4)] for j in xrange(1,4)]
[[1, 2, 3], [2, 4, 6], [3, 6, 9]]

>>> def double(n):
...    """Double and return the input argument."""
...    return n*2

>>> a = double(5)
>>> b = double(['one', 'two'])
>>> print a, b
10 ['one', 'two', 'one', 'two']

>>> print double.__doc__
Double and return the input argument.

>>> def bracket(value, lower=0, upper=None):
...     """Limit a value to a specific range (lower, upper)"""
...     if upper:
...         value = min(value, upper)
...     return max(value, lower)
>>> bracket(2)
2
>>> bracket(2, 3)
3

>>> bracket(2, upper=1)
1

>>> def apply_to_list(func, target_list):
...     return [func(x) for x in target_list]
>>> b = apply_to_list(bracket, range(-3, 5, 2))
>>> print b
[0, 0, 1, 3]

>>> a, b = "global A", "global B"

>>> def foo():
...     b = "local B"
...     print "Function Scope: a=%s, b=%s" % (a, b)

>>> print "Global Scope: a=%s, b=%s" % (a, b)
Global Scope: a=global A, b=global B
>>> foo()
Function Scope: a=global A, b=local B

# mymodule.py
def bracket(value, lower=0, upper=None):
    """Limit a value to a specific range (lower, upper)"""
    if upper:
        value = min(value, upper)
    return max(value, lower)

 def apply_to_list(func, target_list):
     """Apply function func to each element of the target list)"""
     return [func(x) for x in target_list]

>>> import mymodule
>>> x = range(-2, 4)
>>> mymodule.apply_to_list(mymodule.bracket, x)
[0, 0, 0, 1, 2, 3]

>>> import mymodule as m
>>> m.bracket.__doc__
'Limit a value to a specific range (lower, upper)'

>>> from mymodule import bracket
>>> bracket(-5)
0

>>> from mymodule import *
>>> apply_to_list(bracket, [-1, 2, -3])
[0, 2, 0]

#mymodule.py
...
if __name__=='__main__':
    x = [-1, 2, 3]
    x_bracket = apply_to_list(bracket, x)
    print "Original List: %s, Bracketed List: %s" % (x, x_bracket)

>>> import mymodule

for time in simulation_period:
    for organism in world:
        if type(organism) is plant:
            pass
        elif type(organism) is fish:
            swim(organism, time)
        elif type(organism) is dog:
            walk(organism, time)

for time in simulation_period:
    for organism in world:
        organism.update(time)

>>> class Organism(object):
...     pass

>>> first = Organism()
>>> second = Organism()

>>> class Organism(object):
...     def speak(self, name):
...         print "Hi, %s. I'm an organism." % name

>>> some_organism = Organism()
>>> some_organism.speak('Edgy')
Hi, Edgy. I'm an organism.

>>> some_organism.species = "unknown"
>>> print some_organism.species
unknown

>>> class Organism(object):
...     def __init__(self, species):
...         self.species = species

>>> some_organism = Organism("amoeba")
>>> print some_organism.species
amoeba

>>> class MotileOrganism(object):
...    def __init__(self):
...        self.position = 0
...    def move(self):
...        speed = 1
...        self.position += speed
...    def where(self):
...        print "Current position is", self.position

>>> motile_organism = MotileOrganism()
>>> motile_organism.move()
>>> motile_organism.where()
Current position is 1

>>> motile_organism.position = 10

>>> class Organism(object):
...     def __init__(self, species="unknown"):
...         self.species = species
...     def speak(self):
...         print "Hi. I'm a %s." % (self.species)
>>> class MotileOrganism(Organism):
...    def __init__(self, species="unknown"):
...         self.species = species
...         self.position = 0
...    def move(self):
...        self.position += 1
...    def where(self):
...        print "Current position is", self.position
>>> algae = Organism("algae")
>>> amoeba = MotileOrganism("amoeba")
>>> amoeba.speak()
Hi. I'm a amoeba.
>>> amoeba.move()
>>> amoeba.where()
Current position is 1

>>> f = open('workfile', 'r') #Open a file in a readonly mode
>>> f.read() #Read entire file
'This is the first line.\nThis is the second line.\n'
>>> f.seek(0)
>>> f.readline() #Read one line
'This is the first line.\n'

#Use iterator to loop over the lines
>>> f.seek(0)
>>> for line in f:
...    print line,
This is the first line.
This is the second line.

#Write a string to a file
>>> f = open('savefile', 'w')
>>> f.write('This is a test\n')
>>> f.close()

>>> import re
>>> p = re.compile('name=([a-z]+)')

>>> m = p.match('name=bartosz')
>>> m.group()
'name=bartosz'

>>> m = p.search('id=1;name=bartosz;status=student')
>>> m.group()
'name=bartosz'

>>> m.group(1)
'bartosz'

>>> filename = 'nonexisting.file'
>>> try:
...     f = open(filename, 'r')
... except IOError:
...     print 'cannot open:', filename
cannot open: nonexisting.file

>>> for i in range(4):
...     try:
...         if (i % 2) == 1:
...             raise ValueError('index is odd')
...     except ValueError, e:
...         print 'caught exception for %d' % i, e
caught exception for 1 index is odd
caught exception for 3 index is odd