Python open file in write mode IOError

Question

I'm receiving an IOError when trying to create a file using open() in python, which only seems to occur for a single filename. The directories definitely exist and permissions are granted, the loop created around 1000 files successfully. When epic = "CON" in the code below I receive the "No such file or directory" error, but it works fine for other values.

f = open('data\\LSE\\%s.csv' % epic.strip(),'w')
f.write(u.read())
f.close()

Could this be a race issue? The files are created quite quickly.

I'm new to python so if there's something obvious I missed, apologies!

'COD'. There's more weirdness, using the console, open('data\\LSE\\COD',w) gives "Bad File Descriptor" but CAD, CO, CODD all work fine. I also tried testing this in other directories and encounter the same behaviour — user5980
– user5980, Commented Feb 28, 2014 at 22:28
Ah, sorry, COD should be CON, that was the string that I was having issues with — user5980
– user5980, Commented Feb 28, 2014 at 22:31
Michael, I tried both (see my correction, it was actually CON sorry), without a file extension it gives "Bad File Descriptor" and with it gives "No such file or directory" — user5980
– user5980, Commented Feb 28, 2014 at 22:32

dsh · Accepted Answer · 2014-02-28 22:43:21Z

2

The problem is that you are running this code on Windows, which still contains some legacies from MS-DOS 1.0. CON is a special name for the console device. You can't use it as a file name. The earliest versions of MS-DOS did not support directories, nor did they support the so-called "extension" of the 8.3 file naming pattern. As a result, the name is special regardless of the directory and regardless of extension.

Some references:

http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx

Do not use the following reserved names for the name of a file:

CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9. Also avoid these names followed immediately by an extension; for example, NUL.txt is not recommended.

edited Feb 28, 2014 at 22:43

answered Feb 28, 2014 at 22:37

dsh

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user5980 Over a year ago

Thanks dsh, I suppose I'll have to change my stock ticker file naming convention!

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