面向过程与函数式、模块
1. 从文件中取出每一条记录放入列表中,列表的每个元素都是{'name':'egon','sex':'male','age':18,'salary':3000}的形式
with open(r'db.txt',mode='rt', encoding='utf-8') as f: l=[{'name':line.strip().split()[0], 'sex':line.strip().split()[1], 'age':line.strip().split()[2], 'salary':line.strip().split()[3]} for line in f] print(l) print(l)
2. 根据1得到的列表,取出薪资最高的人的信息
res = max(l, key=lambda k: k['salary']) print(res)
3. 根据1得到的列表,取出最年轻的人的信息
younger = min(l,key=lambda dic: dic['age']) print(younger)
4. 将names=['egon','alex_sb','wupeiqi','yuanhao']中的名字全部变大写
names=['egon','alex_sb','wupeiqi','yuanhao'] names=[name.upper() for name in names] print(names) names=['egon','alex_sb','wupeiqi','yuanhao'] # up = [name.upper() lambda name:name.upper()] up = map(lambda name:name.upper(),names) print(list(up))
5. 将names=['egon','alex_sb','wupeiqi','yuanhao']中以sb结尾的名字过滤掉,然后保存剩下的名字长度
names=['egon','alex_sb','wupeiqi','yuanhao'] names = [name for name in names if not name.endswith('sb')] print(names) res = filter(lambda l:not l.endswith('sb'),names) print(list(res))
6. 求文件a.txt中最长的行的长度(长度按字符个数算,需要使用max函数)
with open(r'a.txt', mode='rt', encoding='utf-8') as f: res = max(f, key=lambda line: len(line.strip())) print(len(res.strip())) with open(r'a.txt', mode='rt', encoding='UTF-8') as f: text_len = max([len(line.strip()) for line in f]) print(text_len)
7. 求文件a.txt中总共包含的字符个数?思考为何在第一次之后的n次sum求和得到的结果为0?(需要使用sum函数)
with open(r'a.txt', mode='rt',encoding='utf-8') as f: res = sum(len(line.strip()) for line in f) res1 = sum(len(line.strip()) for line in f) print(res) print(res1)
''' 因为第一次sum求和时即第一次打开文件文件指针在文件开头, 当第一次sum求和完毕后文件指针在文件的末尾 此时当我们再次使用sum求值时由于文件没有关闭, 因此指针一直在文件的末尾因此当第一次之后的n次sum求和结果都为0 '''
8. 思考题
with open('a.txt') as f: g = (len(line) for line in f) print(sum(g)) # 为何报错? #因为当我们在此处打印sum(g)求和时,文件f已经被关闭了,因此会报错
9. 文件shopping.txt内容如下
# mac,20000,3 # lenovo,3000,10 # tesla,1000000,10 # chicken,200,1 # 求总共花了多少钱? with open(r'shopping.txt', mode='rt', encoding='utf-8') as f: res = sum(int(line.strip().split(',')[1]) * int(line.strip().split(',')[2]) for line in f) print(res) with open(r'shopping.txt', mode='rt', encoding='utf-8') as f11: res11 = sum(int(list[1]) * int(list[2]) for list in (line.strip().split(',') for line in f11)) print(res11) # 打印出所有商品的信息,格式为[{'name':'xxx','price':333,'count':3},...] with open(r'shopping.txt', mode='rt', encoding='utf-8') as f1: res1 = [{'name': line.strip().split(',')[0], 'price': line.strip().split(',')[1], 'count': line.strip().split(',')[2]} for line in f1] print(res1) with open(r'shopping.txt', mode='rt', encoding='utf-8') as f2: res2 = [{'name': dic[0], 'price': int(dic[1]), 'count': int(dic[2])} for dic in (line.strip().split(',') for line in f2)] print(res2) # 求单价大于10000的商品信息,格式同上 with open(r'shopping.txt', mode='rt', encoding='utf-8') as f2: res2 = [{'name': dic[0], 'price': int(dic[1]), 'count': int(dic[2])} for dic in (line.strip().split(',') for line in f2)] res3 = filter(lambda dic: dic['price'] > 10000, res2) print(list(res3))
10. 思考:判断下述说法是否正确
# 题目1: # 1、应该将程序所有功能都扔到一个模块中,然后通过导入模块的方式引用它们 (错) # 2、应该只将程序各部分组件共享的那一部分功能扔到一个模块中,然后通过导入模块的方式引用它们 (对) # 题目2: # 运行python文件与导入python文件的区别是什么? ''' 运行python文件指运行python程序 导入python文件指将python文件作为模块,在需要的地方引用模块python文件得功能代码 ''' # 运行的python文件产生的名称空间何时回收,为什么? ''' python文件运行结束后回收,python文件得主程序全部运行完毕后结束对名称空间内名字得使用,名称空间就会被回收 ''' # 导入的python文件产生的名称空间何时回收,为什么? ''' python文件运行结束后回收,因为导入得python文件是模块,只有当主程序运行结束后,被引用得python文件模块才会被回收 '''
11. 二分法
list1 = [1, 3, 5, 7, 9, 11, 13, 15, 17, 18, 22] def func(find_number, l): print(l) if len(l) == 0: print('error') return num = len(l) // 2 if l[num] > find_number: l = l[:num] func(find_number, l) elif l[num] < find_number: l = l[num + 1:] func(find_number, l) else: print('find it') func(2, list1)