2022-05-01 21:31:57 +02:00
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# Collections Module
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``` py
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# COUNTER ()
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# subclass dictionary for counting hash-capable objects
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from collections import Counter
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Counter (sequence) # -> Counter object
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# {item: num included in sequence, ...}
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var = Counter (sequence)
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var.most_common (n) # produce list of most common elements (most common n)
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sum (var.values ()) # total of all counts
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var.clear () #reset all counts
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list (var) # list unique items
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set (var) # convert to a set
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dict (var) # convert to regular dictionary
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var.items () # convert to a list of pairs (element, count)
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Counter (dict (list_of_pairs)) # convert from a list of pairs
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var.most_common [: - n-1: -1] # n less common elements
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var + = Counter () # remove zero and negative counts
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# DEFAULTDICT ()
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# dictionary-like object that takes a default type as its first argument
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# defaultdict will never raise a KeyError exception.
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# non-existent keys return a default value (default_factory)
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from collections import defaultdict
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var = defaultdict (default_factory)
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var.popitem () # remove and return first element
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var.popitem (last = True) # remove and return last item
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# OREDERDDICT ()
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# subclass dictionary that "remembers" the order in which the contents are entered
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# Normal dictionaries have random order
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name_dict = OrderedDict ()
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# OrderedDict with same elements but different order are considered different
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# USERDICT ()
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# pure implementation in pythondi a map that works like a normal dictionary.
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# Designated to create subclasses
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UserDict.data # recipient of UserDict content
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# NAMEDTUPLE ()
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# each namedtuple is represented by its own class
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from collections import namedtuple
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NomeClasse = namedtuple (NomeClasse, parameters_separated_from_space)
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var = ClassName (parameters)
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var.attribute # access to attributes
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var [index] # access to attributes
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var._fields # access to attribute list
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var = class._make (iterable) # transformain namedtuple
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var._asdict () # Return OrderedDict object starting from namedtuple
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# DEQUE ()
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# double ended queue (pronounced "deck")
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# list editable on both "sides"
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from collections import deque
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var = deque (iterable, maxlen = num) # -> deque object
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var.append (item) # add item to the bottom
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var.appendleft (item) # add item to the beginning
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var.clear () # remove all elements
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var.extend (iterable) # add iterable to the bottom
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var.extendleft (iterable) # add iterable to the beginning '
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var.insert (index, item) # insert index position
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var.index (item, start, stop) # returns position of item
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var.count (item)
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var.pop ()
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var.popleft ()
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var.remove (value)
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var.reverse () # reverse element order
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var.rotate (n) # move the elements of n steps (dx if n> 0, sx if n <0)
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var.sort ()
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```
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