python编程从入门到实践第十章习题

    第十章介绍的是文件的读取和写入，以及异常的处理。总的来说，本章还是比较简单的，问题也不是很难。

    打开文件用以下语句：

with open(file_name) as file_obj:

    而关闭文件则用：

file_obj.close()

但是python会自动关闭文件的，人工关闭的话可能会出现错误，所以一般都不需要这条语句的。

读取文件有多种方法：

msg = file_obj.read()    #read all
msg = file_obj.readline() #read a line
msg = file_obj.readlines() #read all lines

对文件有写入操作的话，在打开文件的时候需要设置’w'或者‘a'，‘a'参数使得写入问价时不会删除文件原来的内容，但是如果不需要的话可以不添加参数。

异常处理：

try:
	pass
except:
	pass

#10-1
filename = 'learning_python.txt'
with open(filename) as file_object:
	contents = file_object.read()
	print(contents.rstrip())
print("\n")
with open(filename) as file_object:
	for line in file_object:
		print(line.rstrip())

print('\n')
#方法一
print_list = [] #先定义一个列表
with open(filename) as file_object:
	for line in file_object:
		print_list.append(line)
print(print_list)
#方法二
print('\n')
with open(filename) as file_object:
	lines = file_object.readlines()
print(lines)

#10-2
with open(filename) as file_object:
	for line in file_object:
		print(line.replace('Python','C').rstrip())
#replace()函数为返回一个修改后的结果，但是并不修改字符串本身

#10-3
name = input("Please input your name:\n")
with open('guest.txt','w') as file_object:
	file_object.write(name)
	
#10-4
with open('guest_book.txt','a') as file_obj:
	name = "ds"
	while name != "break":
		name = input("Please input your name,and input break to end:\n")
		file_obj.write(name)


#10-5
with open('reason.txt','a') as file_obj:
	reason = 's'
	while reason != 'a':
		reason = input("Why do you like pyhton? press a to end:\n")
		file_obj.write(reason)

#10-6&7
try:
	with open('number.txt') as file_obj:
		while True:
			try:
				num1 = file_obj.readline()
				num2 = file_obj.readline()
			except:
				print("There is no more digits.")
			else:
				if num1.rstrip().isdigit() and num2.rstrip().isdigit():
					print(int(num1.rstrip())+int(num2.rstrip()))
				# elif num1.rstrip().isdigit() or :
				# 	print("The first input is not number")
				#想判断怎么一个输入不是整数，但是不会0.0
				elif num2.rstrip() == "":
					break
				else:
					print("The input is not numbers!")
except:
	print("There is no txt named number.txt")

输入：

输出：