Mastering Python Second Edition Release Code

libraries/T_08_counter.rst

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+>>> import collections
+
+>>> counter = collections.Counter('eggs')
+>>> for character in 'eggs':
+...     print(f'Count for {character}: {counter[character]}')
+Count for e: 1
+Count for g: 2
+Count for g: 2
+Count for s: 1
+
+------------------------------------------------------------------------------
+
+>>> import math
+>>> import collections
+
+>>> counter = collections.Counter()
+>>> for i in range(0, 100000):
+...    counter[math.sqrt(i) // 25] += 1
+
+>>> for key, count in counter.most_common(5):
+...     print(f'{key}: {count}')
+11.0: 14375
+10.0: 13125
+9.0: 11875
+8.0: 10625
+12.0: 10000
+
+------------------------------------------------------------------------------
+
+>>> import collections
+
+>>> def print_sorted(counter):
+...     sorted_characters = sorted(counter.elements())
+...     print(''.join(sorted_characters))
+
+>>> eggs = collections.Counter('eggs')
+>>> spam = collections.Counter('spam')
+>>> print_sorted(eggs)
+eggs
+>>> print_sorted(spam)
+amps
+>>> print_sorted(eggs & spam)
+s
+>>> print_sorted(spam & eggs)
+s
+>>> print_sorted(eggs - spam)
+egg
+>>> print_sorted(spam - eggs)
+amp
+>>> print_sorted(eggs + spam)
+aeggmpss
+>>> print_sorted(spam + eggs)
+aeggmpss
+>>> print_sorted(eggs | spam)
+aeggmps
+>>> print_sorted(spam | eggs)
+aeggmps

libraries/T_09_deque.rst

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+>>> import collections
+
+>>> queue = collections.deque()
+>>> queue.append(1)
+>>> queue.append(2)
+>>> queue
+deque([1, 2])
+>>> queue.popleft()
+1
+>>> queue.popleft()
+2
+>>> queue.popleft()
+Traceback (most recent call last):
+    ...
+IndexError: pop from an empty deque
+
+------------------------------------------------------------------------------
+
+>>> import collections
+
+>>> queue = collections.deque()
+>>> queue.append(1)
+>>> queue.append(2)
+>>> queue
+deque([1, 2])
+>>> queue.pop()
+2
+>>> queue.pop()
+1
+>>> queue.pop()
+Traceback (most recent call last):
+    ...
+IndexError: pop from an empty deque
+
+------------------------------------------------------------------------------
+
+>>> import collections
+
+>>> circular = collections.deque(maxlen=2)
+>>> for i in range(5):
+...     circular.append(i)
+...     circular
+deque([0], maxlen=2)
+deque([0, 1], maxlen=2)
+deque([1, 2], maxlen=2)
+deque([2, 3], maxlen=2)
+deque([3, 4], maxlen=2)
+>>> circular
+deque([3, 4], maxlen=2)

libraries/T_11_combinations.rst

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+>>> import itertools
+
+>>> list(itertools.combinations(range(3), 2))
+[(0, 1), (0, 2), (1, 2)]
+
+------------------------------------------------------------------------------
+
+>>> import itertools
+
+>>> list(itertools.combinations_with_replacement(range(3), 2))
+[(0, 0), (0, 1), (0, 2), (1, 1), (1, 2), (2, 2)]
+
+------------------------------------------------------------------------------
+
+>>> import itertools
+
+>>> def powerset(iterable):
+...     return itertools.chain.from_iterable(
+...         itertools.combinations(iterable, i)
+...         for i in range(len(iterable) + 1))
+>>> list(powerset(range(3)))
+[(), (0,), (1,), (2,), (0, 1), (0, 2), (1, 2), (0, 1, 2)]

libraries/T_11_namedtuple.rst

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+>>> import collections
+
+>>> Point = collections.namedtuple('Point', ['x', 'y', 'z'])
+>>> point_a = Point(1, 2, 3)
+>>> point_a
+Point(x=1, y=2, z=3)
+
+>>> point_b = Point(x=4, z=5, y=6)
+>>> point_b
+Point(x=4, y=6, z=5)
+
+------------------------------------------------------------------------------
+
+>>> x, y, z = point_a
+>>> print(f'X: {x}, Y: {y}, Z: {z}')
+X: 1, Y: 2, Z: 3
+>>> print('X: {}, Y: {}, Z: {}'.format(*point_b))
+X: 4, Y: 6, Z: 5
+>>> print('X: %d, Y: %d, Z: %d' % point_b)
+X: 4, Y: 6, Z: 5
+>>> print(f'X: {point_a.x}')
+X: 1

libraries/T_12_permutations.rst

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+>>> import itertools
+
+>>> list(itertools.permutations(range(3), 2))
+[(0, 1), (0, 2), (1, 0), (1, 2), (2, 0), (2, 1)]

libraries/T_13_ordereddict.rst

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+>>> import collections
+
+
+>>> spam = collections.OrderedDict()
+>>> spam['b'] = 2
+>>> spam['c'] = 3
+>>> spam['a'] = 1
+>>> spam
+OrderedDict([('b', 2), ('c', 3), ('a', 1)])
+
+>>> for key, value in spam.items():
+...     key, value
+('b', 2)
+('c', 3)
+('a', 1)
+
+>>> eggs = collections.OrderedDict(sorted(spam.items()))
+>>> eggs
+OrderedDict([('a', 1), ('b', 2), ('c', 3)])
+