python之文件读写和异常处理

# 文件读取、写入和异常处理操作举例
# date:2017-07-17

file_name = "D:/file_demo.txt"
with open(file_name, 'w') as write_file_obj:
    '''写入文件'''
    write_file_obj.write("hello\n")
    write_file_obj.write("world\n")

with open(file_name, 'a') as write_file_obj:
    '''追加文件'''
    write_file_obj.write(" ! ")

with open(file_name) as file_obj:
    '''读取文件全部内容'''
    whole_context = file_obj.read()
    print(whole_context.strip())
    print('------------------------')

with open(file_name) as file_obj:
    '''逐行读取文件内容'''
    for line in file_obj:
        print(line.strip())  # 去除左右空格
    print('------------------------')

with open(file_name) as file_obj:
    '''列表形式读取文件内容'''
    lines = file_obj.readlines();
    for line in lines:
        print(line.strip())  # 去除左右空格
    print('------------------------')

file_name = "D:/file_demo_none.txt"
try:
    '''异常处理：文件不存在'''
    with open(file_name) as file_obj:
        whole_context = file_obj.read()
        print(whole_context.strip())
except FileNotFoundError:
    print("File '" + file_name + "' not found!")
else:
    print("File '" + file_name + "' exists!")

　　

运行结果：

hello
world
 !
------------------------
hello
world
!
------------------------
hello
world
!
------------------------
File 'D:/file_demo_none.txt' not found!