Mass Deface a set-like object providing a view on od's keys" return KeysView(self) def viewvalues(self): "od.viewvalues() -> an object providing a view on od's values" return ValuesView(self) def viewitems(self): "od.viewitems() -> a set-like object providing a view on od's items" return ItemsView(self) ################################################################################ ### namedtuple ################################################################################ _class_template = '''\ class {typename}(tuple): '{typename}({arg_list})' __slots__ = () _fields = {field_names!r} def __new__(_cls, {arg_list}): 'Create new instance of {typename}({arg_list})' return _tuple.__new__(_cls, ({arg_list})) @classmethod def _make(cls, iterable, new=tuple.__new__, len=len): 'Make a new {typename} object from a sequence or iterable' result = new(cls, iterable) if len(result) != {num_fields:d}: raise TypeError('Expected {num_fields:d} arguments, got %d' % len(result)) return result def __repr__(self): 'Return a nicely formatted representation string' return '{typename}({repr_fmt})' % self def _asdict(self): 'Return a new OrderedDict which maps field names to their values' return OrderedDict(zip(self._fields, self)) def _replace(_self, **kwds): 'Return a new {typename} object replacing specified fields with new values' result = _self._make(map(kwds.pop, {field_names!r}, _self)) if kwds: raise ValueError('Got unexpected field names: %r' % kwds.keys()) return result def __getnewargs__(self): 'Return self as a plain tuple. Used by copy and pickle.' return tuple(self) {field_defs} ''' _repr_template = '{name}=%r' _field_template = '''\ {name} = _property(_itemgetter({index:d}), doc='Alias for field number {index:d}') ''' def namedtuple(typename, field_names, verbose=False, rename=False): """Returns a new subclass of tuple with named fields. >>> Point = namedtuple('Point', ['x', 'y']) >>> Point.__doc__ # docstring for the new class 'Point(x, y)' >>> p = Point(11, y=22) # instantiate with positional args or keywords >>> p[0] + p[1] # indexable like a plain tuple 33 >>> x, y = p # unpack like a regular tuple >>> x, y (11, 22) >>> p.x + p.y # fields also accessable by name 33 >>> d = p._asdict() # convert to a dictionary >>> d['x'] 11 >>> Point(**d) # convert from a dictionary Point(x=11, y=22) >>> p._replace(x=100) # _replace() is like str.replace() but targets named fields Point(x=100, y=22) """ # Validate the field names. At the user's option, either generate an error # message or automatically replace the field name with a valid name. if isinstance(field_names, basestring): field_names = field_names.replace(',', ' ').split() field_names = map(str, field_names) if rename: seen = set() for index, name in enumerate(field_names): if (not all(c.isalnum() or c=='_' for c in name) or _iskeyword(name) or not name or name[0].isdigit() or name.startswith('_') or name in seen): field_names[index] = '_%d' % index seen.add(name) for name in [typename] + field_names: if not all(c.isalnum() or c=='_' for c in name): raise ValueError('Type names and field names can only contain ' 'alphanumeric characters and underscores: %r' % name) if _iskeyword(name): raise ValueError('Type names and field names cannot be a ' 'keyword: %r' % name) if name[0].isdigit(): raise ValueError('Type names and field names cannot start with ' 'a number: %r' % name) seen = set() for name in field_names: if name.startswith('_') and not rename: raise ValueError('Field names cannot start with an underscore: ' '%r' % name) if name in seen: raise ValueError('Encountered duplicate field name: %r' % name) seen.add(name) # Fill-in the class template class_definition = _class_template.format( typename = typename, field_names = tuple(field_names), num_fields = len(field_names), arg_list = repr(tuple(field_names)).replace("'", "")[1:-1], repr_fmt = ', '.join(_repr_template.format(name=name) for name in field_names), field_defs = '\n'.join(_field_template.format(index=index, name=name) for index, name in enumerate(field_names)) ) if verbose: print class_definition # Execute the template string in a temporary namespace and support # tracing utilities by setting a value for frame.f_globals['__name__'] namespace = dict(_itemgetter=_itemgetter, __name__='namedtuple_%s' % typename, OrderedDict=OrderedDict, _property=property, _tuple=tuple) try: exec class_definition in namespace except SyntaxError as e: raise SyntaxError(e.message + ':\n' + class_definition) result = namespace[typename] # For pickling to work, the __module__ variable needs to be set to the frame # where the named tuple is created. Bypass this step in enviroments where # sys._getframe is not defined (Jython for example) or sys._getframe is not # defined for arguments greater than 0 (IronPython). try: result.__module__ = _sys._getframe(1).f_globals.get('__name__', '__main__') except (AttributeError, ValueError): pass return result ######################################################################## ### Counter ######################################################################## class Counter(dict): '''Dict subclass for counting hashable items. Sometimes called a bag or multiset. Elements are stored as dictionary keys and their counts are stored as dictionary values. >>> c = Counter('abcdeabcdabcaba') # count elements from a string >>> c.most_common(3) # three most common elements [('a', 5), ('b', 4), ('c', 3)] >>> sorted(c) # list all unique elements ['a', 'b', 'c', 'd', 'e'] >>> ''.join(sorted(c.elements())) # list elements with repetitions 'aaaaabbbbcccdde' >>> sum(c.values()) # total of all counts 15 >>> c['a'] # count of letter 'a' 5 >>> for elem in 'shazam': # update counts from an iterable ... c[elem] += 1 # by adding 1 to each element's count >>> c['a'] # now there are seven 'a' 7 >>> del c['b'] # remove all 'b' >>> c['b'] # now there are zero 'b' 0 >>> d = Counter('simsalabim') # make another counter >>> c.update(d) # add in the second counter >>> c['a'] # now there are nine 'a' 9 >>> c.clear() # empty the counter >>> c Counter() Note: If a count is set to zero or reduced to zero, it will remain in the counter until the entry is deleted or the counter is cleared: >>> c = Counter('aaabbc') >>> c['b'] -= 2 # reduce the count of 'b' by two >>> c.most_common() # 'b' is still in, but its count is zero [('a', 3), ('c', 1), ('b', 0)] ''' # References: # http://en.wikipedia.org/wiki/Multiset # http://www.gnu.org/software/smalltalk/manual-base/html_node/Bag.html # http://www.demo2s.com/Tutorial/Cpp/0380__set-multiset/Catalog0380__set-multiset.htm # http://code.activestate.com/recipes/259174/ # Knuth, TAOCP Vol. II section 4.6.3 def __init__(self, iterable=None, **kwds): '''Create a new, empty Counter object. And if given, count elements from an input iterable. Or, initialize the count from another mapping of elements to their counts. >>> c = Counter() # a new, empty counter >>> c = Counter('gallahad') # a new counter from an iterable >>> c = Counter({'a': 4, 'b': 2}) # a new counter from a mapping >>> c = Counter(a=4, b=2) # a new counter from keyword args ''' super(Counter, self).__init__() self.update(iterable, **kwds) def __missing__(self, key): 'The count of elements not in the Counter is zero.' # Needed so that self[missing_item] does not raise KeyError return 0 def most_common(self, n=None): '''List the n most common elements and their counts from the most common to the least. If n is None, then list all element counts. >>> Counter('abcdeabcdabcaba').most_common(3) [('a', 5), ('b', 4), ('c', 3)] ''' # Emulate Bag.sortedByCount from Smalltalk if n is None: return sorted(self.iteritems(), key=_itemgetter(1), reverse=True) return _heapq.nlargest(n, self.iteritems(), key=_itemgetter(1)) def elements(self): '''Iterator over elements repeating each as many times as its count. >>> c = Counter('ABCABC') >>> sorted(c.elements()) ['A', 'A', 'B', 'B', 'C', 'C'] # Knuth's example for prime factors of 1836: 2**2 * 3**3 * 17**1 >>> prime_factors = Counter({2: 2, 3: 3, 17: 1}) >>> product = 1 >>> for factor in prime_factors.elements(): # loop over factors ... product *= factor # and multiply them >>> product 1836 Note, if an element's count has been set to zero or is a negative number, elements() will ignore it. ''' # Emulate Bag.do from Smalltalk and Multiset.begin from C++. return _chain.from_iterable(_starmap(_repeat, self.iteritems())) # Override dict methods where necessary @classmethod def fromkeys(cls, iterable, v=None): # There is no equivalent method for counters because setting v=1 # means that no element can have a count greater than one. raise NotImplementedError( 'Counter.fromkeys() is undefined. Use Counter(iterable) instead.') def update(self, iterable=None, **kwds): '''Like dict.update() but add counts instead of replacing them. Source can be an iterable, a dictionary, or another Counter instance. >>> c = Counter('which') >>> c.update('witch') # add elements from another iterable >>> d = Counter('watch') >>> c.update(d) # add elements from another counter >>> c['h'] # four 'h' in which, witch, and watch 4 ''' # The regular dict.update() operation makes no sense here because the # replace behavior results in the some of original untouched counts # being mixed-in with all of the other counts for a mismash that # doesn't have a straight-forward interpretation in most counting # contexts. Instead, we implement straight-addition. Both the inputs # and outputs are allowed to contain zero and negative counts. if iterable is not None: if isinstance(iterable, Mapping): if self: self_get = self.get for elem, count in iterable.iteritems(): self[elem] = self_get(elem, 0) + count else: super(Counter, self).update(iterable) # fast path when counter is empty else: self_get = self.get for elem in iterable: self[elem] = self_get(elem, 0) + 1 if kwds: self.update(kwds) def subtract(self, iterable=None, **kwds): '''Like dict.update() but subtracts counts instead of replacing them. Counts can be reduced below zero. Both the inputs and outputs are allowed to contain zero and negative counts. Source can be an iterable, a dictionary, or another Counter instance. >>> c = Counter('which') >>> c.subtract('witch') # subtract elements from another iterable >>> c.subtract(Counter('watch')) # subtract elements from another counter >>> c['h'] # 2 in which, minus 1 in witch, minus 1 in watch 0 >>> c['w'] # 1 in which, minus 1 in witch, minus 1 in watch -1 ''' if iterable is not None: self_get = self.get if isinstance(iterable, Mapping): for elem, count in iterable.items(): self[elem] = self_get(elem, 0) - count else: for elem in iterable: self[elem] = self_get(elem, 0) - 1 if kwds: self.subtract(kwds) def copy(self): 'Return a shallow copy.' return self.__class__(self) def __reduce__(self): return self.__class__, (dict(self),) def __delitem__(self, elem): 'Like dict.__delitem__() but does not raise KeyError for missing values.' if elem in self: super(Counter, self).__delitem__(elem) def __repr__(self): if not self: return '%s()' % self.__class__.__name__ items = ', '.join(map('%r: %r'.__mod__, self.most_common())) return '%s({%s})' % (self.__class__.__name__, items) # Multiset-style mathematical operations discussed in: # Knuth TAOCP Volume II section 4.6.3 exercise 19 # and at http://en.wikipedia.org/wiki/Multiset # # Outputs guaranteed to only include positive counts. # # To strip negative and zero counts, add-in an empty counter: # c += Counter() def __add__(self, other): '''Add counts from two counters. >>> Counter('abbb') + Counter('bcc') Counter({'b': 4, 'c': 2, 'a': 1}) ''' if not isinstance(other, Counter): return NotImplemented result = Counter() for elem, count in self.items(): newcount = count + other[elem] if newcount > 0: result[elem] = newcount for elem, count in other.items(): if elem not in self and count > 0: result[elem] = count return result def __sub__(self, other): ''' Subtract count, but keep only results with positive counts. >>> Counter('abbbc') - Counter('bccd') Counter({'b': 2, 'a': 1}) ''' if not isinstance(other, Counter): return NotImplemented result = Counter() for elem, count in self.items(): newcount = count - other[elem] if newcount > 0: result[elem] = newcount for elem, count in other.items(): if elem not in self and count < 0: result[elem] = 0 - count return result def __or__(self, other): '''Union is the maximum of value in either of the input counters. >>> Counter('abbb') | Counter('bcc') Counter({'b': 3, 'c': 2, 'a': 1}) ''' if not isinstance(other, Counter): return NotImplemented result = Counter() for elem, count in self.items(): other_count = other[elem] newcount = other_count if count < other_count else count if newcount > 0: result[elem] = newcount for elem, count in other.items(): if elem not in self and count > 0: result[elem] = count return result def __and__(self, other): ''' Intersection is the minimum of corresponding counts. >>> Counter('abbb') & Counter('bcc') Counter({'b': 1}) ''' if not isinstance(other, Counter): return NotImplemented result = Counter() for elem, count in self.items(): other_count = other[elem] newcount = count if count < other_count else other_count if newcount > 0: result[elem] = newcount return result if __name__ == '__main__': # verify that instances can be pickled from cPickle import loads, dumps Point = namedtuple('Point', 'x, y', True) p = Point(x=10, y=20) assert p == loads(dumps(p)) # test and demonstrate ability to override methods class Point(namedtuple('Point', 'x y')): __slots__ = () @property def hypot(self): return (self.x ** 2 + self.y ** 2) ** 0.5 def __str__(self): return 'Point: x=%6.3f y=%6.3f hypot=%6.3f' % (self.x, self.y, self.hypot) for p in Point(3, 4), Point(14, 5/7.): print p class Point(namedtuple('Point', 'x y')): 'Point class with optimized _make() and _replace() without error-checking' __slots__ = () _make = classmethod(tuple.__new__) def _replace(self, _map=map, **kwds): return self._make(_map(kwds.get, ('x', 'y'), self)) print Point(11, 22)._replace(x=100) Point3D = namedtuple('Point3D', Point._fields + ('z',)) print Point3D.__doc__ import doctest TestResults = namedtuple('TestResults', 'failed attempted') print TestResults(*doctest.testmod())