需要读取的文件内容：http://python.itcarlow.ie/chapter3/sketch.txt

1. 切换工作目录

代码：

import os
os.chdir('D:/')    # 注意斜杠方向
print(os.getcwd())

输出：

D:\

2. 打开文件open()

代码：

try:
    data = open('sketch.txt')
    print(data.readline(), end='')    # 读取一行内容
    print(data.readline(), end='')    # 读取二行内容
    data.seek(0)    # 返回文件起始位置
except IOError:
    print('The data file is missing!')

输出：

Man: Is this the right room for an argument?
Other Man: I've told you once.
0

3. 输出所有内容

代码：

for each_line in data:
    try:
        (role, line_spoken) = each_line.split(':', 1)
        print(role, end='')
        print(' said: ', end='')
        print(line_spoken, end='')
    except ValueError:    # 因为数据中存在多个冒号和没有冒号的数据，需要处理产生的错误，
        print(each_line)

部分输出：

Man said:  Is this the right room for an argument?
Other Man said:  I've told you once.
... ...
Man said:  (exasperated) Oh, this is futile!!
Other Man said:  No it isn't!
Man said:  Yes it is!

4. 关闭文件

代码：

if 'data' in locals():
    data.close()

# 或者使用with打开文件，则不需要手动close：
with open('sketch.txt', 'w') as data:

5. 完整代码

try:
    with open('sketch.txt') as data:
        for each_line in data:
            try:
                (role, line_spoken) = each_line.split(':', 1)    # split('', 1)处理多个冒号的情况，只分一次；
                print(role, end='')
                print(' said: ', end='')
                print(line_spoken, end='')
            except ValueError:    # 因为数据中存在没有冒号的数据，需要处理产生的错误；
                print(each_line)
except IOError as err:
    print('IOError: ' + str(err))