Python3实用编程技巧进阶一

Python3实用编程技巧进阶一

01-字典列表集合中筛选

# 如何在列表字典集合中根据条件帅选数据from random import randint# 第一种# data = [-1,2,3,-4,5]# res = []# for x in data:# if x > 0:# res.append(x)# print(res)# a = randint(-10,10)# print(a)b = [randint(-10,10) for _ in range(10)]# print(b)# 第二种# 列表解析b2 = [x for x in b if x >= 0]# print(b2)# 第三种filter函数# 返回一个生成器对象 next可以取出元素b3 = filter(lambda x:x>=0,b)# print(next(b3))# print(list(b3))# 第四种 字典d = {'student%d' % i : randint(50,100) for i in range(1,21) }# print(d)# 获取分数高于90的学生d1 = {k:v for k,v in d.items() if v >=90}# print(d1)g = filter(lambda item:item[1],d.items())# print(list(g))g = filter(lambda item:item[1],d.items())# print(dict(g))# 第五种集合s = {randint(0,20) for _ in range(20)}print(s)s1 = {x for x in s if x %3 == 0}print(s1)

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02-枚举

# 举例from enum import Enum, unique# @unique# class Color(Enum):# red = 1# red_alias = 2## print(Color['red'])# print(Color.red.name)# print(Color.red.value)class Color(Enum): red = 1 orange = 2 yellow = 3 green = 4 blue = 5 indigo = 6 purple = 7 red_alias = 1for color in Color: print(color)for color in Color.__members__.items(): print(color)print(Color['red'])print(Color['red'].name)print(Color['red'].value)for i in Color: print(i.name,'->',i.value)

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03-具名元组

04-根据字典值的大小对字典中的项排序

#将字典中的各项转换为元组 使用内置函数sorted排序#包含元组的列表是可以排序的（元组是可以比较大小的）# print((3,2) > (1,4))"""依次从前到后比较返回 True"""from random import randint#第一种方法d = {k:randint(60,100) for k in 'abcdefg'}# print(d)l = [(v,k) for k ,v in d.items()]# print(l)l = sorted(l,reverse=True)# print(l)"""True{'a': 87, 'b': 89, 'c': 86, 'd': 60, 'e': 99, 'f': 77, 'g': 87}[(87, 'a'), (89, 'b'), (86, 'c'), (60, 'd'), (99, 'e'), (77, 'f'), (87, 'g')][(99, 'e'), (89, 'b'), (87, 'g'), (87, 'a'), (86, 'c'), (77, 'f'), (60, 'd')]"""#第二种d = {k:randint(60,100) for k in 'abcdefg'}# print(d)l = list(zip(d.values(),d.keys()))# print(l)l = sorted(l,reverse=True)# print(l)"""True{'a': 72, 'b': 92, 'c': 85, 'd': 65, 'e': 75, 'f': 69, 'g': 62}[(72, 'a'), (92, 'b'), (85, 'c'), (65, 'd'), (75, 'e'), (69, 'f'), (62, 'g')][(92, 'b'), (85, 'c'), (75, 'e'), (72, 'a'), (69, 'f'), (65, 'd'), (62, 'g')]"""#第三种d = {k:randint(60,100) for k in 'abcdefg'}print(d.items())l=sorted(d.items(),key=lambda item:item[1],reverse=True)print(l)p = list(enumerate(l,1))print(p)t={}for i ,(k,v) in p: print(i,k,v) t[k] = (i,v)print(t)"""Truedict_items([('a', 96), ('b', 85), ('c', 85), ('d', 71), ('e', 87), ('f', 98), ('g', 82)])[('f', 98), ('a', 96), ('e', 87), ('b', 85), ('c', 85), ('g', 82), ('d', 71)][(1, ('d', 95)), (2, ('a', 93)), (3, ('f', 93)), (4, ('c', 91)), (5, ('b', 67)), (6, ('e', 67)), (7, ('g', 62))]1 d 1002 c 943 a 884 b 805 g 736 f 707 e 68{'a': (1, 98), 'g': (2, 90), 'f': (3, 84), 'e': (4, 80), 'd': (5, 66), 'c': (6, 65), 'b': (7, 60)}"""

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05如何统计序列中元素的频度

from random import randint#随机生成一个列表 有重复的数字data = [randint(0,20) for _ in range(30)]print(data)#[16, 3, 6, 0, 4, 20, 1, 0, 13, 16, 13, 6, 14, 13, 16, 4, 14, 9, 12, 5, 4, 6, 1, 7, 18, 5, 6, 15, 14, 5]#列表每个元素作为键，值默认为0（出现个数）d= dict.fromkeys(data,0)print(d)#{16: 0, 3: 0, 6: 0, 0: 0, 4: 0, 20: 0, 1: 0, 13: 0, 14: 0, 9: 0, 12: 0, 5: 0, 7: 0, 18: 0, 15: 0}#迭代列表 遇到某个数值就+1 统计数字出现个数for x in data: d[x] += 1print(d)#{16: 3, 3: 1, 6: 4, 0: 2, 4: 3, 20: 1, 1: 2, 13: 3, 14: 3, 9: 1, 12: 1, 5: 3, 7: 1, 18: 1, 15: 1}p = sorted([(v,k) for k,v in d.items()],reverse=True)print(p)#[(5, 19), (2, 17), (2, 16), (2, 12), (2, 8), (2, 6), (2, 4), (2, 3), (2, 1), (2, 0), (1, 20), (1, 15), (1, 14), (1, 10), (1, 9), (1, 7), (1, 2)]

05.1 collection 统计频率

from random import randintfrom collections import Counter#随机生成一个列表 有重复的数字data = [randint(0,20) for _ in range(30)]# print(data)p = Counter(data)l=p.most_common(3)print(p)print(l)Counter({4: 4, 11: 3, 6: 3, 7: 3, 3: 2, 17: 2, 9: 2, 20: 2, 0: 2, 10: 1, 16: 1, 2: 1, 13: 1, 15: 1, 12: 1, 18: 1})[(4, 4), (11, 3), (6, 3)]

6，如何快速找到多个字典中的公共键key

第一种:

from random import randint,sample# print(sample('abcdefgh',3))#['g', 'e', 'b'] 随机d1={k:randint(1,4) for k in sample('abcdefgh',randint(3,6)) }# print(d1)#随机返回3-6名球员 和 进球数#{'d': 2, 'f': 1, 'e': 1, 'g': 3, 'c': 3, 'b': 2}d2={k:randint(1,4) for k in sample('abcdefgh',randint(3,6)) }d3={k:randint(1,4) for k in sample('abcdefgh',randint(3,6)) }dl = [d1,d2,d3]#3轮都有进球的球员print( [k for k in dl[0] if all(map(lambda d:k in d,dl[1:]))])#解释#map(lambda d:k in d,dl[1:]) 和PHP的array_map一样的作用#判断k 是否在d2,d3中 all()表示全在

第二种方法：

from random import randint,samplefrom functools import reduce# print(sample('abcdefgh',3))#['g', 'e', 'b'] 随机d1={k:randint(1,4) for k in sample('abcdefgh',randint(3,6)) }# print(d1)#随机返回3-6名球员 和 进球数#{'d': 2, 'f': 1, 'e': 1, 'g': 3, 'c': 3, 'b': 2}d2={k:randint(1,4) for k in sample('abcdefgh',randint(3,6)) }d3={k:randint(1,4) for k in sample('abcdefgh',randint(3,6)) }dl = [d1,d2,d3]#3轮都有进球的球员print(d1.keys())print(dict.keys(d1))d = map(dict.keys,dl)dd = reduce(lambda a,b:a & b,map(dict.keys,dl))print(dd)dict_keys(['f', 'b', 'a', 'c', 'e', 'd'])dict_keys(['f', 'b', 'a', 'c', 'e', 'd']){'f', 'd', 'a', 'b'}

7，如何让字典保持有序

from collections import OrderedDictfrom random import shufflefrom itertools import isliceod = OrderedDict()od['c'] = 1od['b'] = 2od['a'] = 3print(od.keys())players = list('abcdefgh')shuffle(players)print(players)od = OrderedDict()for i,p in enumerate(players,1): od[p] = iprint(od)def queryByOrder(d,a,b=None): a -= 1 if b is None: b = a+1 return list(islice(od,a,b))print(queryByOrder(od,2,4))odict_keys(['c', 'b', 'a'])['c', 'd', 'a', 'e', 'b', 'g', 'f', 'h']OrderedDict([('c', 1), ('d', 2), ('a', 3), ('e', 4), ('b', 5), ('g', 6), ('f', 7), ('h', 8)])['d', 'a', 'e']

8,如何实现用户历史记录功能

from random import randintdef guess(n,k): if n == k: print('猜对了，这个数字是%d.' % k) return True; if n < k: print('猜大了，比%d小.' % k) elif n > k: print('猜小了，比%d大.' % k) return Falsedef main(): n = randint(1,100) i = 1 while True: line = input('[%d] 请输入一个数字：' % i) if line.isdigit(): k = int(line) i += 1 if guess(n,k): break elif line == 'quit': breakif __name__ == '__main__': main()

[1] 请输入一个数字：24猜小了，比24大.[2] 请输入一个数字：56猜小了，比56大.[3] 请输入一个数字：4猜小了，比4大.[4] 请输入一个数字：

from collections import dequeq = deque([],5)q.append(1)q.append(2)q.append(3)q.append(4)q.append(5)print(q)q.append(6)print(q)deque([1, 2, 3, 4, 5], maxlen=5)deque([2, 3, 4, 5, 6], maxlen=5)

1 from random import randint 2 from collections import deque 3 def guess(n,k): 4 if n == k: 5 print('猜对了，这个数字是%d.' % k) 6 return True; 7 if n < k: 8 print('猜大了，比%d小.' % k) 9 elif n > k:10 print('猜小了，比%d大.' % k)11 12 return False13 14 def main():15 n = randint(1,100)16 i = 117 hq = deque([],5)18 while True:19 line = input('[%d] 请输入一个数字：' % i)20 if line.isdigit():21 k = int(line)22 hq.append(k)23 i += 124 if guess(n,k):25 break26 elif line == 'quit':27 break28 elif line == 'h?':29 print(list(hq))30 31 if __name__ == '__main__':32 main()

改良版增加deque

pickle模块：

from collections import dequeimport pickleq = deque([],5)q.append(1)q.append(2)q.append(3)q.append(4)q.append(5)print(q)q.append(6)print(q)# pickle.dump(q,open('save.pkl','wb'))b = pickle.load(open('save.pkl','rb'))print(b)deque([1, 2, 3, 4, 5], maxlen=5)deque([2, 3, 4, 5, 6], maxlen=5)deque([2, 3, 4, 5, 6], maxlen=5)

pickle

pickle保存文件格式

�ccollectionsdequeq )K�qRq(KKKKKe.

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