Python文件的读写和异常代码示例

#!/usr/bin/env python
with open('pi') as file_object:
  contents = file_object.read()
  print(contents)
 
===================================
3.1415926
 5212533
 2324255

#!/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

#!/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

#!/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

#!/usr/bin/env python
filename = 'programming.txt'
with open(filename,'w') as file_object:
  file_object.write("I love programming!")

#!/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")

#!/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")

#!/usr/bin/env python
 
try:
  print(5/0)
except ZeroDivisionError:
  print("You cant divide by zero!")

try:
<语句>    #运行别的代码
except <名字>：
<语句>    #如果在try部份引发了'name'异常
except <名字>，<数据>:
<语句>    #如果引发了'name'异常，获得附加的数据
else:
<语句>    #如果没有异常发生

#!/usr/bin/python
# -*- coding: UTF-8 -*-
try:
  fh = open("testfile", "w")
  fh.write("这是一个测试文件，用于测试异常!!")
except IOError:
  print "Error: 没有找到文件或读取文件失败"
else:
  print "内容写入文件成功"
  fh.close()

$ python test.py 
内容写入文件成功
$ cat testfile    # 查看写入的内容
这是一个测试文件，用于测试异常!!

#!/usr/bin/python
# -*- coding: UTF-8 -*-

try:
  fh = open("testfile", "w")
  fh.write("这是一个测试文件，用于测试异常!!")
except IOError:
  print "Error: 没有找到文件或读取文件失败"
else:
  print "内容写入文件成功"
  fh.close()

chmod -w testfile

$ python test.py 
Error: 没有找到文件或读取文件失败