Python 基础（九） | time random collections itertools 标准库详解

import time
t_local = time.localtime()t_UTC = time.gmtime()print("t_local", t_local)           # 本地时间print("t_UTC", t_UTC)               # UTC统一时间

t_local time.struct_time(tm_year=2022, tm_mon=9, tm_mday=29, tm_hour=8, tm_min=54, tm_sec=24, tm_wday=3, tm_yday=272, tm_isdst=0)t_UTC time.struct_time(tm_year=2022, tm_mon=9, tm_mday=29, tm_hour=0, tm_min=54, tm_sec=24, tm_wday=3, tm_yday=272, tm_isdst=0)

time.ctime()                      # 返回本地时间的字符串

'Thu Sep 29 09:00:53 2022'

t_1_start = time.time()t_2_start = time.perf_counter()t_3_start = time.process_time()print(t_1_start)print(t_2_start)print(t_3_start)
res = 0for i in range(1000000):    res += i    time.sleep(5)t_1_end = time.time()t_2_end = time.perf_counter()t_3_end = time.process_time()
print("time方法：{:.3f}秒".format(t_1_end-t_1_start))print("perf_counter方法：{:.3f}秒".format(t_2_end-t_2_start))print("process_time方法：{:.3f}秒".format(t_3_end-t_3_start))

1567068710.72695456009.08140642.25time方法：5.128秒perf_counter方法：5.128秒process_time方法：0.125秒

lctime = time.localtime()time.strftime("%Y-%m-%d %A %H:%M:%S", lctime)

'2022-09-29 Thursday 09:01:54'

from random import *
seed(10)print(random())seed(10)print(random())

0.57140259468991350.5714025946899135

print(random())

0.4288890546751146

numbers = [randint(1,10) for i in range(10)]numbers

[3, 5, 6, 3, 8, 4, 8, 10, 7, 1]

numbers = [randrange(10) for i in range(10)]numbers

[6, 3, 0, 0, 7, 4, 9, 1, 8, 1]

numbers = [randrange(0, 10, 2) for i in range(10)]numbers

[2, 6, 8, 4, 8, 2, 0, 0, 6, 2]

numbers = [random() for i in range(10)]numbers

[0.9819392547566425, 0.19092611184488173, 0.3486810954900942, 0.9704866291141572, 0.4456072691491385, 0.6807895695768549, 0.14351321471670841, 0.5218569500629634, 0.8648825892767497, 0.26702706855337954]

numbers = [uniform(2.1, 3.5) for i in range(10)]numbers

[2.523598043850906, 3.0245903649048116, 3.4202356766870463, 2.344031169179946, 2.3465252151503173, 3.181989084829388, 2.5592895031615703, 2.413131937436849, 2.8627907782614415, 2.16114212173462]

choice(['win', 'lose', 'draw'])

'draw'

choice("python")

'h'

choices(['win', 'lose', 'draw'], k=5)

['draw', 'lose', 'draw', 'draw', 'draw']

choices(['win', 'lose', 'draw'], [4,4,2], k=10)

['lose', 'draw', 'lose', 'win', 'draw', 'lose', 'draw', 'win', 'win', 'lose']

numbers = ["one", "two", "three", "four"]shuffle(numbers)numbers

['four', 'one', 'three', 'two']

sample([10, 20, 30, 40, 50], k=3)

[20, 30, 10]

number = gauss(0, 1)number

0.6331522345532208

import matplotlib.pyplot as plt
res = [gauss(0, 1) for i in range(100000)]
plt.hist(res, bins=1000)plt.show()

import random

def red_packet(total, num):    for i in range(1, num):        per = random.uniform(0.01, total/(num-i+1)*2)          # 保证每个人获得红包的期望是total/num        total = total - per        print("第{}位红包金额： {:.2f}元".format(i, per))    else:        print("第{}位红包金额： {:.2f}元".format(num, total))                        red_packet(10, 5)

第1位红包金额： 1.85元第2位红包金额： 3.90元第3位红包金额： 0.41元第4位红包金额： 3.30元第5位红包金额： 0.54元

import randomimport numpy as np

def red_packet(total, num):    ls = []    for i in range(1, num):        per = round(random.uniform(0.01, total/(num-i+1)*2), 2)     # 保证每个人获得红包的期望是total/num        ls.append(per)        total = total - per    else:        ls.append(total)            return ls                        # 重复发十万次红包，统计每个位置的平均值（约等于期望）res = []for i in range(100000):    ls = red_packet(10,5)    res.append(ls)
res = np.array(res)print(res[:10])np.mean(res, axis=0)

[[1.71 1.57 0.36 1.25 5.11] [1.96 0.85 1.46 3.29 2.44] [3.34 0.27 1.9  0.64 3.85] [1.99 1.08 3.86 1.69 1.38] [1.56 1.47 0.66 4.09 2.22] [0.57 0.44 1.87 5.81 1.31] [0.47 1.41 3.97 1.28 2.87] [2.65 1.82 1.22 2.02 2.29] [3.16 1.2  0.3  3.66 1.68] [2.43 0.16 0.11 0.79 6.51]]




array([1.9991849, 2.0055725, 2.0018144, 2.0022472, 1.991181 ])

import randomimport string
print(string.digits)print(string.ascii_letters)
s=string.digits + string.ascii_lettersv=random.sample(s,4)print(v)print(''.join(v))

0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ['n', 'Q', '4', '7']nQ47

import collections

p = (1, 2)

collections.namedtuple(typename, field_names, *, rename=False, defaults=None, module=None)

Point = collections.namedtuple("Point", ["x", "y"])p = Point(1, y=2)p

Point(x=1, y=2)

print(p.x)print(p.y)

12

print(p[0])print(p[1])x, y = pprint(x)print(y)

1212

print(isinstance(p, tuple))

True

Card = collections.namedtuple("Card", ["rank", "suit"])ranks = [str(n) for n in range(2, 11)] + list("JQKA")    suits = "spades diamonds clubs hearts".split()print("ranks", ranks)print("suits", suits)cards = [Card(rank, suit) for rank in ranks                          for suit in suits]cards

ranks ['2', '3', '4', '5', '6', '7', '8', '9', '10', 'J', 'Q', 'K', 'A']suits ['spades', 'diamonds', 'clubs', 'hearts']
[Card(rank='2', suit='spades'), Card(rank='2', suit='diamonds'), Card(rank='2', suit='clubs'), Card(rank='2', suit='hearts'), Card(rank='3', suit='spades'), Card(rank='3', suit='diamonds'), Card(rank='3', suit='clubs'), Card(rank='3', suit='hearts'), Card(rank='4', suit='spades'), Card(rank='4', suit='diamonds'), Card(rank='4', suit='clubs'), Card(rank='4', suit='hearts'), Card(rank='5', suit='spades'), Card(rank='5', suit='diamonds'), Card(rank='5', suit='clubs'), Card(rank='5', suit='hearts'), Card(rank='6', suit='spades'), Card(rank='6', suit='diamonds'), Card(rank='6', suit='clubs'), Card(rank='6', suit='hearts'), Card(rank='7', suit='spades'), Card(rank='7', suit='diamonds'), Card(rank='7', suit='clubs'), Card(rank='7', suit='hearts'), Card(rank='8', suit='spades'), Card(rank='8', suit='diamonds'), Card(rank='8', suit='clubs'), Card(rank='8', suit='hearts'), Card(rank='9', suit='spades'), Card(rank='9', suit='diamonds'), Card(rank='9', suit='clubs'), Card(rank='9', suit='hearts'), Card(rank='10', suit='spades'), Card(rank='10', suit='diamonds'), Card(rank='10', suit='clubs'), Card(rank='10', suit='hearts'), Card(rank='J', suit='spades'), Card(rank='J', suit='diamonds'), Card(rank='J', suit='clubs'), Card(rank='J', suit='hearts'), Card(rank='Q', suit='spades'), Card(rank='Q', suit='diamonds'), Card(rank='Q', suit='clubs'), Card(rank='Q', suit='hearts'), Card(rank='K', suit='spades'), Card(rank='K', suit='diamonds'), Card(rank='K', suit='clubs'), Card(rank='K', suit='hearts'), Card(rank='A', suit='spades'), Card(rank='A', suit='diamonds'), Card(rank='A', suit='clubs'), Card(rank='A', suit='hearts')]

from random import *

# 洗牌shuffle(cards)cards

[Card(rank='J', suit='hearts'), Card(rank='A', suit='hearts'), Card(rank='3', suit='hearts'), Card(rank='8', suit='hearts'), Card(rank='K', suit='hearts'), Card(rank='7', suit='spades'), Card(rank='5', suit='hearts'), Card(rank='A', suit='spades'), Card(rank='10', suit='spades'), Card(rank='J', suit='diamonds'), Card(rank='K', suit='clubs'), Card(rank='4', suit='spades'), Card(rank='2', suit='diamonds'), Card(rank='Q', suit='spades'), Card(rank='A', suit='clubs'), Card(rank='A', suit='diamonds'), Card(rank='6', suit='hearts'), Card(rank='7', suit='diamonds'), Card(rank='5', suit='diamonds'), Card(rank='10', suit='clubs'), Card(rank='8', suit='clubs'), Card(rank='9', suit='clubs'), Card(rank='6', suit='clubs'), Card(rank='6', suit='diamonds'), Card(rank='5', suit='clubs'), Card(rank='3', suit='diamonds'), Card(rank='4', suit='hearts'), Card(rank='3', suit='clubs'), Card(rank='7', suit='hearts'), Card(rank='2', suit='spades'), Card(rank='J', suit='clubs'), Card(rank='9', suit='spades'), Card(rank='J', suit='spades'), Card(rank='10', suit='hearts'), Card(rank='2', suit='clubs'), Card(rank='8', suit='diamonds'), Card(rank='6', suit='spades'), Card(rank='10', suit='diamonds'), Card(rank='9', suit='hearts'), Card(rank='3', suit='spades'), Card(rank='8', suit='spades'), Card(rank='Q', suit='clubs'), Card(rank='Q', suit='hearts'), Card(rank='5', suit='spades'), Card(rank='7', suit='clubs'), Card(rank='4', suit='clubs'), Card(rank='2', suit='hearts'), Card(rank='K', suit='diamonds'), Card(rank='K', suit='spades'), Card(rank='Q', suit='diamonds'), Card(rank='4', suit='diamonds'), Card(rank='9', suit='diamonds')]

# 随机抽一张牌choice(cards)

Card(rank='4', suit='hearts')

# 随机抽多张牌sample(cards, k=5)

[Card(rank='4', suit='hearts'), Card(rank='2', suit='clubs'), Card(rank='Q', suit='diamonds'), Card(rank='9', suit='spades'), Card(rank='10', suit='hearts')]

from collections import Counter

s = "牛奶奶找刘奶奶买牛奶"colors = ['red', 'blue', 'red', 'green', 'blue', 'blue']cnt_str = Counter(s)cnt_color = Counter(colors)print(cnt_str)print(cnt_color)

Counter({'奶': 5, '牛': 2, '找': 1, '刘': 1, '买': 1})Counter({'blue': 3, 'red': 2, 'green': 1})

print(isinstance(Counter(), dict))

True

cnt_color.most_common(2)

[('blue', 3), ('red', 2)]

list(cnt_str.elements())

['牛', '牛', '奶', '奶', '奶', '奶', '奶', '找', '刘', '买']

c = Counter(a=3, b=1)d = Counter(a=1, b=2)c+d

Counter({'a': 4, 'b': 3})

cards = collections.Counter(tens=16, low_cards=36)seen = sample(list(cards.elements()), k=10)print(seen)

['tens', 'low_cards', 'low_cards', 'low_cards', 'tens', 'tens', 'low_cards', 'low_cards', 'low_cards', 'low_cards']

seen.count('tens') / 10

0.3

from collections import deque
d = deque('cde') d

deque(['c', 'd', 'e'])

d.append("f")            # 右端增加d.append("g")d.appendleft("b")        # 左端增加d.appendleft("a")d

deque(['a', 'b', 'c', 'd', 'e', 'f', 'g'])

d.pop()           # 右端删除 d.popleft()       # 左端删除d

deque(['b', 'c', 'd', 'e', 'f'])

import itertools
for i in itertools.product('ABC', '01'):    print(i)

('A', '0')('A', '1')('B', '0')('B', '1')('C', '0')('C', '1')

for i in itertools.product('ABC', repeat=3): # 相当于3组ABC的笛卡尔积    print(i)

('A', 'A', 'A')('A', 'A', 'B')('A', 'A', 'C')('A', 'B', 'A')('A', 'B', 'B')('A', 'B', 'C')('A', 'C', 'A')('A', 'C', 'B')('A', 'C', 'C')('B', 'A', 'A')('B', 'A', 'B')('B', 'A', 'C')('B', 'B', 'A')('B', 'B', 'B')('B', 'B', 'C')('B', 'C', 'A')('B', 'C', 'B')('B', 'C', 'C')('C', 'A', 'A')('C', 'A', 'B')('C', 'A', 'C')('C', 'B', 'A')('C', 'B', 'B')('C', 'B', 'C')('C', 'C', 'A')('C', 'C', 'B')('C', 'C', 'C')

for i in itertools.permutations('ABCD', 3):   # 3 是排列的长度    print(i)

('A', 'B', 'C')('A', 'B', 'D')('A', 'C', 'B')('A', 'C', 'D')('A', 'D', 'B')('A', 'D', 'C')('B', 'A', 'C')('B', 'A', 'D')('B', 'C', 'A')('B', 'C', 'D')('B', 'D', 'A')('B', 'D', 'C')('C', 'A', 'B')('C', 'A', 'D')('C', 'B', 'A')('C', 'B', 'D')('C', 'D', 'A')('C', 'D', 'B')('D', 'A', 'B')('D', 'A', 'C')('D', 'B', 'A')('D', 'B', 'C')('D', 'C', 'A')('D', 'C', 'B')

for i in itertools.permutations(range(3)):    print(i)

(0, 1, 2)(0, 2, 1)(1, 0, 2)(1, 2, 0)(2, 0, 1)(2, 1, 0)

for i in itertools.combinations('ABCD', 2):  # 2是组合的长度    print(i)

('A', 'B')('A', 'C')('A', 'D')('B', 'C')('B', 'D')('C', 'D')

for i in itertools.combinations(range(4), 3):    print(i)

(0, 1, 2)(0, 1, 3)(0, 2, 3)(1, 2, 3)

for i in itertools.combinations_with_replacement('ABC', 2):  # 2是组合的长度    print(i)

('A', 'A')('A', 'B')('A', 'C')('B', 'B')('B', 'C')('C', 'C')

for i in itertools.product('ABC',repeat=2):    print(i)

('A', 'A')('A', 'B')('A', 'C')('B', 'A')('B', 'B')('B', 'C')('C', 'A')('C', 'B')('C', 'C')

for i in zip("ABC", "012", "xyz"):    print(i)

('A', '0', 'x')('B', '1', 'y')('C', '2', 'z')

for i in zip("ABC", [0, 1, 2, 3, 4, 5]):          # 注意zip是内置的，不需要加itertools    print(i)

('A', 0)('B', 1)('C', 2)

for i in itertools.zip_longest("ABC", "012345"):    print(i)

('A', '0')('B', '1')('C', '2')(None, '3')(None, '4')(None, '5')

for i in itertools.zip_longest("ABC", "012345", fillvalue = "?"):    print(i)

('A', '0')('B', '1')('C', '2')('?', '3')('?', '4')('?', '5')

创建一个迭代器，它从 start 值开始，返回均匀间隔的值

itertools.count(10)101112...

创建一个迭代器，返回 iterable 中所有元素，无限重复

itertools.cycle("ABC")ABCABC...

创建一个迭代器，不断重复 object 。除非设定参数 times ，否则将无限重复

for i in itertools.repeat(10, 3):    print(i)

101010

把一组迭代对象串联起来，形成一个更大的迭代器

for i in itertools.chain('ABC', [1, 2, 3]):    print(i)

ABC123

产出由两个元素组成的元组，结构是（index, item）,其中index 从start开始，item从iterable中取

for i in enumerate("Python", start=1):    print(i)

(1, 'P')(2, 'y')(3, 't')(4, 'h')(5, 'o')(6, 'n')

创建一个迭代器，按照key指定的方式，返回 iterable 中连续的键和组一般来说，要预先对数据进行排序key为None默认把连续重复元素分组

for key, group in itertools.groupby('AAAABBBCCDAABBB'):    print(key, list(group))

A ['A', 'A', 'A', 'A']B ['B', 'B', 'B']C ['C', 'C']D ['D']A ['A', 'A']B ['B', 'B', 'B']

animals = ["duck", "eagle", "rat", "giraffe", "bear", "bat", "dolphin", "shark", "lion"]animals.sort(key=len)print(animals)

['rat', 'bat', 'duck', 'bear', 'lion', 'eagle', 'shark', 'giraffe', 'dolphin']

for key, group in itertools.groupby(animals, key=len):    print(key, list(group))

3 ['rat', 'bat']4 ['duck', 'bear', 'lion']5 ['eagle', 'shark']7 ['giraffe', 'dolphin']

animals = ["duck", "eagle", "rat", "giraffe", "bear", "bat", "dolphin", "shark", "lion"]animals.sort(key=lambda x: x[0])print(animals)for key, group in itertools.groupby(animals, key=lambda x: x[0]):    print(key, list(group))

['bear', 'bat', 'duck', 'dolphin', 'eagle', 'giraffe', 'lion', 'rat', 'shark']b ['bear', 'bat']d ['duck', 'dolphin']e ['eagle']g ['giraffe']l ['lion']r ['rat']s ['shark']