Writing file-写入文件

-写入文件内容使用write方法，该方法在文件中写入字符串，如：

file=open('newfile.txt','w')
file.write('This has been written to a file')
file.close()
file=open('newfile.txt','r')
print file.read()
file.close()

执行结果：

>>>
This has been written to a file
>>>

当一个文件以写的模式被打开时，文件中存在的内容会被删除，如：

file=open('newfile.txt','r')
print 'Readin initial contents'
print file.read()
print 'Finished'
file.close()

file=open('newfile.txt','w')
file.write('some new text')
file.close()

file=open('newfile.txt','r')
print 'Reading new contents'
print file.read()
print 'Finished'
file.close()

执行结果:

>>>
>Reading initial contents
some initial text
Finished
Reading new conents
some new text
Finished
>>>

如果写入文件成功的话，write方法返回被写入文件内容的字节数(在python2x版本中可能不同），如：

msg='hello world!'
file=open('newfile.txt','w')
count=file.write(msg)
print count
file.close()

执行结果：

>>>
>12
>>>