4种非常实用的python内置数据结构

 from array import array l = list(range(100)) a = array.fromlist(l) print(l.__sizeof__(), a.__sizeof__()) 

 a = array('i') a.append(1) a.append(4) 

 import collections students = ['Zhang San', 'Li Si', 'Zhou liu', 'Chen qi', 'Cheng ba'] # using defaultdict dd = collections.defaultdict(list) for s in students: key = s[0] dd[key].append(s) print(dd) # using original dict (method 1) od = {} for s in students: key = s[0] if key not in do: od[key] = [] od[key].append(s) print(od) scores = ['A', 'B', 'C', 'A', 'A', 'B', 'C', 'B', 'A', 'A'] # using defaultdict dd = collections.defaultdict(int) for s in scores : dd[s] += 1 print(dd) # using original dict (method 2) od = collections.defaultdict(int) for s in scores : if s not in do: do[s] = 1 else: do[s] += 1 print(od) 

 # class class Rect: def __init__(self, x1, y1, x2, y2): self.x1 = x1 self.y1 = y1 self.x2 = x2 self.y2 = y2 def area_class(r): w = r.x2 - r.x1 h = r.y2 - r.y1 return w*h r1 = Rect(1,3,5,5) # <__main__.Rect object at 0x7fde252a87f0> # to show its content, we need to implement __repr__(self) or __str__(self) print(area_class(r1)) # tuple def area_tuple(r): w = r[2]-r[0] h = r[3]-r[1] return w*h r2 = (1,3,5,5) print(r2) # (1, 3, 5, 5) print(area_tuple(r2)) # dict def area_dict(r): w = r["x2"] - r["x1"] h = r["y2"] - r["y1"] return w*h r3 = {"x1":1, "y1":3, "x2":5, "y2":5} print(r3) # {'x1': 1, 'y1': 3, 'x2': 5, 'y2': 5} print(area_tuple(r3)) # named tuple import collections Rectangle = collections.namedtuple("Rectangle", ["x1", "y1", "x2", "y2"]) def area_namedtuple(r): w = r.x2 - r.x1 y = r.y2 - r.y1 return w*h r4 = Rectangle(1,3,5,5) print(r4) # Rectangle(x1=1, y1=3, x2=5, y2=5) x1,y2,x2,y2 = r4 print(x1,y2,x2,y2) # 1 3 5 5 print(area_namedtuple(r4)) print(area_class(r4)) # work with "." grammar print(area_tuple(r4)) # work with index print(area_dict(r4._asdict())) # work with dict 

 c = Counter()                           # a new, empty counter c = Counter('gallahad')                 # a new counter from an iterable print(c) # Counter({'a': 3, 'l': 2, 'g': 1, 'h': 1, 'd': 1}) c = Counter({'red': 4, 'blue': 2})      # a new counter from a mapping print(c) # Counter({'red': 4, 'blue': 2}) c = Counter(cats=4, dogs=8)             # a new counter from keyword args print(c) # Counter({'dogs': 8, 'cats': 4}) 

 c = Counter(a=4, b=2, c=0, d=-2) sorted(c.elements()) # ['a', 'a', 'a', 'a', 'b', 'b'] Counter('abracadabra').most_common(3) # [('a', 5), ('b', 2), ('r', 2)] c1 = Counter(a=4, b=2, d=-2) c2 = Counter(a=1, b=2, c=3, d=4) c1.subtract(c2) c1 # Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6})