10-3 访客 :编写一个程序,提示用户输入其名字;用户作出响应后,将其名字写入到文件guest.txt中。
代码:
filename = 'guest.txt' guest_name = input("Please input your name: ") with open(filename, 'w') as file_object: file_object.write(guest_name)
结果:(生成文本)
Tom
10-4 访客名单 :编写一个while 循环,提示用户输入其名字。用户输入其名字后,在屏幕上打印一句问候语,并将一条访问记录添加到文件guest_book.txt中。确保这个文件中的每条记录都独占一行。
代码:
filename = 'guest.txt' guest_name = input("Please input your name: (input 'q' to quit)") while guest_name!='q': with open(filename, 'a') as file_object: file_object.write(guest_name + '\n') guest_name = input("Please input your name: (input 'q' to quit)")
结果:(输入Tom, Tim)
Tom Tim
10-6 加法运算 :提示用户提供数值输入时,常出现的一个问题是,用户提供的是文本而不是数字。在这种情况下,当你尝试将输入转换为整数时,将引发TypeError 异常。编写一个程序,提示用户输入两个数字,再将它们相加并打印结果。在用户输入的任何一个值不是数字时都捕获TypeError 异常,并打印一条友好的错误消息。对你编写的程序进行测试:先输入两个数字,再输入一些文本而不是数字。
代码:
a = input("Please input the first number: ") b = input("Please input the second number: ") try: a=int(a) b=int(b) except ValueError: print("Sorry, the type of txt can't be calculated.") else: c= a+b print(c)
结果:
(输入是3,4)
7(输入是3,da)
Sorry, the type of txt can't be calculated.
10-7 加法计算器 :将你为完成练习10-6而编写的代码放在一个while 循环中,让用户犯错(输入的是文本而不是数字)后能够继续输入数字。
代码:c=0 i=0 while i<2: a = input("Please input the second number: ") try: a=int(a) except ValueError: print("Sorry, the type of txt can't be calculated.") else: i+=1 c+=a print(c)
结果:
Please input the second number: 3 Please input the second number: da Sorry, the type of txt can't be calculated. Please input the second number: 1ad2 Sorry, the type of txt can't be calculated. Please input the second number: 31 34
10-8 猫和狗 :创建两个文件cats.txt和dogs.txt,在第一个文件中至少存储三只猫的名字,在第二个文件中至少存储三条狗的名字。编写一个程序,尝试读取这些文件,并将其内容打印到屏幕上。将这些代码放在一个try-except 代码块中,以便在文件不存在时捕获FileNotFound 错误,并打印一条友好的消息。将其中一个文件移到另一个地方,并确认except 代码块中的代码将正确地执行。
代码:def OpenFile(filename): try: with open (filename) as file_object: line = file_object.readlines() except FileNotFoundError: print("Sorry, the file "+filename+" can't be found.") else: for line_ in line: print(line_.rstrip()) filename = "cat.txt" OpenFile(filename) filename = "dog.txt" OpenFile(filename)
结果:
(文件不在)
cat1 cat2 cat3 Sorry, the file dog.txt can't be found.(文件在文件夹中)
cat1 cat2 cat3 dog1 dog2 dog3
10-12 记住喜欢的数字 :将练习10-11中的两个程序合而为一。如果存储了用户喜欢的数字,就向用户显示它,否则提示用户输入他喜欢的数字并将其存储到文件中。运行这个程序两次,看看它是否像预期的那样工作。
代码:
import json def get_stored_number(): filename="user.json" try: with open(filename) as f_obj: number = json.load(f_obj) except FileNotFoundError: return None else: return number def greet_user(): number = get_stored_number() number = number if number: print("The number you like is: " + str(number)) else: number = input("Please input the number you like: ") filename = "user.json" with open(filename,"w") as f_obj: json.dump(number,f_obj) print("We'll remember the number you like when you come back!") greet_user()
结果:
(文件不存在时)
Please input the number you like: 8 We'll remember the number you like when you come back!
(存储数字后)
The number you like is: 8