Python中实用的库函数

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from collections import dequed=deque([1,2,3]) # 使用list初始化d.append(1) # 队尾添加元素d.appendleft(1) # 队头添加元素d.pop() # 队尾移除元素d.popleft() # 队头移除元素d.extend([4,5,6]) # 队尾添加多个元素d.extendleft([4,5,6]) # 队头添加多个元素

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from queue import PriorityQueueq = PriorityQueue()q.put((2, 'code'))q.put((1, 'eat'))q.put((3, 'sleep'))while not q.empty(): next_item = q.get() print(next_item)# 结果：# (1, 'eat')# (2, 'code')# (3, 'sleep')

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import heapqq = []heapq.heappush(q, (2, 'code'))heapq.heappush(q, (1, 'eat'))heapq.heappush(q, (3, 'sleep'))while q: next_item = heapq.heappop(q) print(next_item)# 结果：# (1, 'eat')# (2, 'code')# (3, 'sleep')# 将一个数组初始化为堆结构heapq.heapify([3,2,1])

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from collections import defaultdicts = 'mississippi'd = defaultdict(int)for k in s: d[k] += 1print(d) # defaultdict(<class 'int'>, {'m': 1, 'i': 4, 's': 4, 'p': 2})d = defaultdict(list)d['a'].append(1)print(d) # defaultdict(<class 'list'>, {'a': [1]})

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from collections import OrderedDictuser_dict = OrderedDict()user_dict['b'] = '0xbug'user_dict['a'] = '0bug'user_dict['c'] = '1bug'# popitem 弹出最后一个组print(user_dict) # OrderedDict([('b', '0xbug'), ('a', '0bug'), ('c', '1bug')])print(user_dict.popitem()) # ('c', '1bug')print(user_dict) # OrderedDict([('b', '0xbug'), ('a', '0bug')])# popitem 弹出第一个组print(user_dict) # OrderedDict([('b', '0xbug'), ('a', '0bug'), ('c', '1bug')])print(user_dict.popitem(last=False)) # ('b', '0xbug')print(user_dict) # OrderedDict([('a', '0bug'), ('c', '1bug')])# pop弹出指定元素，必须写参数print(user_dict) # OrderedDict([('b', '0xbug'), ('a', '0bug'), ('c', '1bug')])print(user_dict.pop('a')) # 0bugprint(user_dict) # OrderedDict([('b', '0xbug'), ('c', '1bug')])# move_to_end将指定元素移至最后print(user_dict) # OrderedDict([('b', '0xbug'), ('a', '0bug'), ('c', '1bug')])print(user_dict.move_to_end('a')) # 0bugprint(user_dict) # OrderedDict([('b', '0xbug'), ('c', '1bug'), ('a', '0bug')])# 获取第一个值print(user_dict) # OrderedDict([('b', '0xbug'), ('a', '0bug'), ('c', '1bug')])print(next(iter(user_dict.values()))) # 0xbug

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from sortedcontainers import SortedListsl = SortedList()sl.add(num)sl.pop(0) # remove index 0sl.pop() # equals s1.pop(-1)s1.remove(num)

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from sortedcontainers import SortedDictsd = SortedDict({'c': 3, 'a': 1, 'b': 2})print(sd) #SortedDict({'a': 1, 'b': 2, 'c': 3})

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from collections import Counterobj = Counter('aabbccc')obj['d'] += 1print(obj) # Counter({'c': 3, 'a': 2, 'b': 2, 'd': 1})

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class UnionFind: def __init__(self,n): self.un=list(range(n)) def find(self,p): if self.un[p]!=p: self.un[p]=self.find(self.un[p]) return self.un[p] def merge(self,p,q): pr=self.find(p) qr=self.find(q) if pr!=qr: self.un[pr]=qr def connect(self,p,q): return self.find(p)==self.find(q)

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class Trie: def __init__(self): self.children={} self.cnt=0 def add(self,s): curr=self for c in s: if not c in curr.children: curr.children[c]=Trie() curr=curr.children[c] curr.cnt+=1 def get(self,s): curr=self for c in s: if not c in curr.children: return 0 curr=curr.children[c] return curr.cnt

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import bisect# 插入操作bisect.insort_left([1,2],1) # 插入在左侧，无返回值bisect.insort_right([1,2],1) # 插入在右侧，无返回值# 查找操作bisect.bisect_left([1,2],1) # 不插入值，返回左侧的索引，输出：0bisect.bisect_right([1,2],1) # 不插入值，返回右侧的索引，输出：1# 下面两行就是insort_right和bisect_right的别名bisect.insort([1,2],1) # 插入在右侧bisect.bisect([1,2],1) # 不插入值，返回右侧的索引

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import random# 浮点数[0,1)random.random()# 浮点数[2,6]random.uniform(2, 6)# 整数[6,8]random.randint(6,8)# 随机返回range中的一个元素random.randrange(0, 31, 2) # 输出[0,30]内的偶数# 随机返回集合中的一个元素random.choice([1,2,3])# 随机打乱集合，无返回arr=[1,2,3,4,5]random.shuffle(arr)print(arr)# 从列表中随机返回3个元素，作为新列表返回random.sample([1,2,3,4,5], 3)

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import itertoolsimport operator if __name__ == '__main__': data = [1, 2, 3, 4, 5] # 计算前缀和 print(list(itertools.accumulate(data))) # [1,3,6,10,15] # 计算到当前位置累积相乘得结果 data = [3, 4, 6, 2, 1, 9, 0, 7, 5, 8] print(list(itertools.accumulate(data, operator.mul, initial=2))) # [2,6,24,144,288,288,2592,0,0,0,0] # 计算到当前位置的最大值并且输出 print(list(itertools.accumulate(data, max))) # [3,4,6,6,6,9,9,9,9,9]

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import itertoolsfor i in itertools.product('ABCD', repeat = 2): print(i)# 输出# ('A', 'A') ('A', 'B') ('A', 'C') ('A', 'D') ('B', 'A') ('B', 'B') ('B', 'C') ('B', 'D') # ('C', 'A') ('C', 'B') ('C', 'C') ('C', 'D') ('D', 'A') ('D', 'B') ('D', 'C') ('D', 'D')

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import itertoolsfor i in itertools.permutations('ABCD', 2): print(i)# 输出# ('A', 'B') ('A', 'C') ('A', 'D') ('B', 'A') ('B', 'C') ('B', 'D') ('C', 'A') ('C', 'B') # ('C', 'D') ('D', 'A') ('D', 'B') ('D', 'C')

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import itertoolsfor i in itertools.combinations('ABCD', 2): print(i)# 输出# ('A', 'B') ('A', 'C') ('A', 'D') ('B', 'C') ('B', 'D') ('C', 'D')

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import itertoolsfor i in itertools.combinations_with_replacement('ABCD', 2): print(i)# 输出# ('A', 'A') ('A', 'B') ('A', 'C') ('A', 'D') ('B', 'B') ('B', 'C') ('B', 'D') ('C', 'C') # ('C', 'D') ('D', 'D')