4

I'm trying to open file using 'os.open()' as below 

>>> filePath
'C:\\Shashidhar\\text.csv'
>>> fd = os.open(filePath,os.O_CREAT)
>>> with os.fdopen(fd, 'w') as myfile:
...    myfile.write("hello")

IOError: [Errno 9] Bad file descriptor

>>>

Any idea how can I open the file object from os.fdopen using "with" so that connection can be closed automatially?

Thanks

Shashi
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    why are you trying to open a file this way and not with the standard `open()` or even, `io.open()`? – monkut Oct 24 '13 at 05:20
  • I have set os.nice(19) before that. And I would like to make use of os to create and open files so that I will have "niceness" while performing this operations! – Shashi Oct 24 '13 at 05:22
  • @Shashi. I don't understand. What has `os.nice` to do with `os.open`? – glglgl Oct 25 '13 at 10:40

2 Answers2

3

use this form, it worked. 

with os.fdopen(os.open(filepath,os.O_CREAT | os.O_RDWR ),'w') as fd:  
    fd.write("abcd")
glglgl
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LearningC
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1

To elaborate on Rohith's answer, they way you are opening the file is important.

The with works by internally calling seleral functions, so I tried it out step by step:

>>> fd = os.open("c:\\temp\\xyxy", os.O_CREAT)
>>> f = os.fdopen(fd, 'w')
>>> myfile = f.__enter__()
>>> myfile.write("213")
>>> f.__exit__()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IOError: [Errno 9] Bad file descriptor

What? Why? And why now?

If I do the same with

>>> fd = os.open(filepath, os.O_CREAT | os.O_RDWR)

all works fine.

With write() you only wrote to the file object's output puffer, and f.__exit__() essentiall calls f.close(), which in turn calls f.flush(), which flushes this output buffer to disk - or, at least, tries to do so.

But it fails, as the file is not writable. So a [Errno 9] Bad file descriptor occurs.

Community
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glglgl
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