Python 文件和异常

一、从文件中读取数据

#!/usr/bin/env python

with open('pi') as file_object:
    contents = file_object.read()
    print(contents)

===================================
3.1415926
  5212533
  2324255

1、逐行读取

#!/usr/bin/env python

filename = 'pi'

with open(filename) as file_object:
    for line in file_object:
        print(line)

===================================
3.1415926

  5212533

  2324255

#!/usr/bin/env python

filename = 'pi'

with open(filename) as file_object:
    for line in file_object:
        print(line.rstrip())

==================
3.1415926
  5212533
  2324255

2、创建一个包含文件各行内容的列表

#!/usr/bin/env python

filename = 'pi'

with open(filename) as file_object:
    lines = file_object.readlines()     #readlines()方法是从文件中读取每一行，并将其存储在一个列表中

for line in lines:
    print(line.rstrip())

==============================
3.1415926
  5212533
  2324255

3、使用文件内容

#!/usr/bin/env python

filename = 'pi'

with open(filename) as file_object:
    lines = file_object.readlines()

pi_string = ''
for line in lines:
    pi_string += line.strip()

print(pi_string)
print(len(pi_string))

========================================
3.141592652125332324255
23

二、写入文件

1、写入空文件

#!/usr/bin/env python

filename = 'programming.txt'

with open(filename,'w') as file_object:
    file_object.write("I love programming!")

2、写入多行

#!/usr/bin/env python

filename = 'programming.txt'

with open(filename,'w') as file_object:
    file_object.write("I love programming!\n")
    file_object.write("yes!\n")

3、附加到文件

#!/usr/bin/env python

filename = 'pi'

with open(filename,'a') as file_object:
    file_object.write("I love programming!\n")
    file_object.write("yes!\n")

三、异常

1、使用try-except代码块

#!/usr/bin/env python

try:
    print(5/0)
except ZeroDivisionError:
    print("You cant divide by zero!")