高级编程技术 课后作业十（第5周）

10-1 Python学习笔记 ：在文本编辑器中新建一个文件，写几句话来总结一下你至此学到的Python知识，其中每一行都以“In Python you can”打头。将这个文件命名为learning_python.txt，并将其存储到为完成本章练习而编写的程序所在的目录中。编写一个程序，它读取这个文件，并将你所写的内容打印三次：第一次打印时读取整个文件；第二次打印时遍历文件对象；第三次打印时将各行存储在一个列表中，再在with 代码块外打印它们。

with open ('note.txt') as file_object:
	print(file_object.read().rstrip())

10-2 C语言学习笔记 ：可使用方法replace() 将字符串中的特定单词都替换为另一个单词。

with open ('note.txt') as file_object:
	lines = file_object.readlines();

for line in lines:
	print(line.replace('Python','C').rstrip())

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。

with open ('guest_book.txt','a') as file_object:
	while True:
		name = input("What's your name(input quit to quit):")
		if name == 'quit':
			break
		file_object.write(name+'\n')

10-5 关于编程的调查 ：编写一个while 循环，询问用户为何喜欢编程。每当用户输入一个原因后，都将其添加到一个存储所有原因的文件中。

with open ('reason.txt','a') as file_object:
	while True:
		name = input("Why do you like promgramming(input quit to quit):")
		if name == 'quit':
			break
		file_object.write(name+'\n')

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。

while True:
	print()
	addend = input("What's the addend(Enter 'q' to quit):")
	if addend == 'q':
		break
	try:
		addend = int(addend)
	except ValueError:
		print("Sorry, the " + addend + " is not a digit.")
		continue
	augend = input("What's the augend(Enter 'q' to quit):")
	if augend == 'q':
		break
	try:
		augend = int(augend)
	except ValueError:
		print("Sorry, the " + augend + " is not a digit.")
		continue
		
	print("The result of " + str(addend) + " plus " + str(augend) + " is " + str(addend + augend) + ".")

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

def animal_name(filename):
	try:
		with open(filename) as fileobject:
			lines = fileobject.readlines()
	except FileNotFoundError:
		print("Sorry, the file " + filename + " does not exist.")
	else:
		print(filename + ":")
		for line in lines:
			print(line.rstrip())

animals = ["cat.txt","dog.txt"]
for animal in animals:
	animal_name(animal)
	print()

10-9 沉默的猫和狗 ：修改你在练习10-8中编写的except 代码块，让程序在文件不存在时一言不发。

def animal_name(filename):
	try:
		with open(filename) as fileobject:
			lines = fileobject.readlines()
	except FileNotFoundError:
		pass
	else:
		print(filename + ":")
		for line in lines:
			print(line.rstrip())

animals = ["cat.txt","dog.txt"]
for animal in animals:
	animal_name(animal)

10-10 常见单词 ：编写一个程序，它读取你在项目Gutenberg中获取的文件，并计算单词'the' 在每个文件中分别出现了多少次。

try:
	with open("The American Journal of Archaeology.txt") as fileobject:
		lines = fileobject.readlines()
except FileNotFoundError:
	print("Sorry, the file The American Journal of Archaeology.txt does not found.")
else:
	amount_the = 0
	for line in lines:
		amount_the += line.lower().count('the')
	print("The word 'the' appears " + str(amount_the) + " times.")
	
		

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。

import json

favorite_number = input("What's you favorite number? ")
file_name = "favorite_number.json"

with open(file_name,'w') as file_object:
	json.dump(favorite_number,file_object)
	
try:
	with open(file_name) as file_object:
		favorite_number = json.load(file_object)
		print("I knowyour favorite number! It's " + favorite_number)
except FileNotFoundError:
	favorite_number = input("What's you favorite number?")
	with open(file_name,'w') as file_object:
		json.dump(favorite_number,file_object)
		print("I knowyour favorite number! It's " + favorite_number)