第二章 数据结构相关话题
1、如何在列表、字典、集合中根据条件筛选数据
#列表
from random import randint
data = [randint(-10,10) for _ in range(10)]
list(filter(lambda x :x >=0, data))
[x for x in data if x >= 0] #更快一些
#字典
data1 = {x: randint(60,100) for x in range(1,20)}
{k: v for k,v in data1.items() if v>=90}
#集合
data2 = set(data)
{x for x in data2 if x % 3==0}
2、如何给元组中的每个元素命名,提高程序可读
student = ('Jim', 16, 'male', '[email protected]')
NAME, AGE, SEX, EMAIL = list(range(4))
print(student[NAME])#可读
from collections import namedtuple #返回内置元组的子类
Student = namedtuple('Student', {'name','age','sex','email'}) #类的工厂
s = Student('Jim', 16, 'male', '[email protected]')
print(s.name) #直接用类对象形式访问元组
print(isinstance(s,tuple)) #true
3、如何统计上出序列中元素的出现频度
#统计字典的频数
from random import randint
d = [randint(0,20) for _ in range(30)]
c = dict.fromkeys(d, 0)#data作为键
for i in d:
c[i] += 1
#sorted函数返回一个list，a = sorted(c)
from collections import Counter
c2 = Counter(d)
c2.most_common(3)
#统计英文词频
import re
txt = open(r'C:\Users\Windows\Desktop\word_count.txt').read()
word = re.split('\W+', txt)#以非字母的正则表达式来进行分割
c3 = Counter(word)
c3.most_common(10)
4、如何根据字典中值的大小，对字典的项进行排序
from random import randint
d = {x：randint（60，,10）for x in 'xyzabc'}
sorted(d)#对键比较
#利用zip将字典数据转化为元组
sorted(zip(d.values(), d.keys()))
#利用sorted的key参数
sorted(d.items(), key=lambda x :x[1], reverse=True)
#利用operator
import operator
sorted(d.items(), key=operator.itemgetter(1))
5、公共键（快速在多个字典里寻找）
from random import randint, sample
d = [{i: randint(1,4) for i in sample('abcdefgh', randint(3,6))} for _ in range(5)]
s1 = {i: randint(1,4) for i in sample('abcdefgh', randint(3,6))}
s2 = {i: randint(1,4) for i in sample('abcdefgh', randint(3,6))}
s3 = {i: randint(1,4) for i in sample('abcdefgh', randint(3,6))}
#常用方式
res = []
for k in s1:
if k in s2 and k in s3:
res.append(k)
#map得到所有键的集合，reduce函数迭代
list(map(dict.keys,[s1, s2, s3]))
from functools import reduce
reduce(lambda a, b: a & b, list(map(dict.keys, [s1, s2, s3])))
6、如何让字典有序
# orderedDict()
from collections import orderedDict
from random import randint
from time import time
start = time()
#d = {}无序
d = orderedDict()
players = 'abcdefgh'
for i in range(len(players)):
input()
index = players.pop(randint(0, len(players) - i)
d[index] = (i+1, end-start)
end = time()
print(i+1, index, end-start)
print('~'*20)
for i in d:
print(i, ':', d[i])
7、如何实现用户的历史记录功能
# deque
from collections import deque
from random import randint
import pickle
import os
queue = deque([], 5) # 第一个值为初始值，第二个为大小
def guess(item):
if item == target:
print('Bingo!')
return True
if item < target:
print('less than target')
elif item > target:
print('greater than target')
return False
if os.path.exists('history'):
pickle.load(open(r'D:\PythonWork\working_study\history', 'rb'))
target = randint(1, 100)
print(target)
while True:
string = input('please input a number(1-100):')
if string == '?' or string == '0':
print(queue)
elif string.isdigit():
data = int(string)
queue.append(data)
if guess(data):
pickle.dump(queue, open(r'D:\PythonWork\working_study\history', 'wb'))
break
if os.path.exists('history'):
his = pickle.load(open(r'D:\PythonWork\working_study\history', 'rb'))
print(his)
第三章 迭代器与生成器相关话题
1、如何实现可迭代对象和迭代器对象
# Iterator， Iterable
import requests
def weather(city):
r = requests.get(u'http://wthrcdn.etouch.cn/weather_mini?city=' + city)
data = r.json()['data']['forecast'][1]
print(('日期: %s, 高温: %s, 天气: %s') % (data['date'], data['high'], data['type']))
weather('武汉')
weather('北京')
from collections import Iterable, Iterator
class WeatherIterator(Iterator):
def __init__(self, city_list):
self.city_list = city_list
self.index = 0
def get_weather(self, city):
r = requests.get(u'http://wthrcdn.etouch.cn/weather_mini?city=' + city)
data = r.json()['data']['forecast'][1]
print(('日期: %s, 高温: %s, 天气: %s') % (data['date'], data['high'], data['type']))
return '%s, %s, %s' % (city, data['low'], data['high'])
def next(self):
if self.index == len(self.city_list):
raise StopIteration
city = self.city_list[self.index]
self.index += 1
return self.get_weather(city)
class WeatherIterable(Iterable):
def __init__(self, cities):
self.cities = cities
def __iter__(self):
# 返回迭代器的一个实例
return WeatherIterator(self.cities)
cities = ['武汉', '北京', '上海', '广州', '深圳', '成都', '重庆', '厦门', '香港']
for x in WeatherIterable(cities):
print(x)
第四章 字符串处理相关话题
1、如何拆分含有多种分隔符的字符串
1