I think it has to do with the terminal the process is attached to. I got this error when I run a python process in the background and closed the terminal in which I started it:

$ myprogram.py
Ctrl-Z
 exit

The problem was that I started a not daemonized process in a remote server and logged out (closing the terminal session). A solution was to start a screen/tmux session on the remote server and start the process within this session. Then detaching the session+log out keeps the terminal associated with the process. This works at least in the *nix world.

The Exception has an errno attribute:

try:
    fp = open("nothere")
except IOError as e:
    print(e.errno)
    print(e)

This is a Windows bug that was fixed with Windows 10 Version 1803. (see https://bugs.python.org/issue32245 and https://github.com/Microsoft/vscode/issues/36630#issuecomment-385759625 )

It affects Python 3.6+ when using code paths that call WriteFile, i.e. os.write and legacy standard I/O mode, and also always affects Python 2.7 and Python 3.5.

prints are implemented in terms of writes which ultimately result in a write(2) call to the kernel. You could run strace on those two samples and (after wading through a lot of chaff) see the same resultant calls to write(2).

Indeed, I just did that and omitting 2000+ lines of output yielded:

execve("/usr/bin/python", ["python", "a.py"], [/* 43 vars */]) = 0
open("print.txt", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3
write(3, "test_print\n", 11)            = 11
close(3)                                = 0

and

execve("/usr/bin/python", ["python", "b.py"], [/* 43 vars */]) = 0
open("write.txt", O_WRONLY|O_CREAT|O_TRUNC|O_LARGEFILE, 0666) = 3
write(3, "test_write\n", 11)            = 11
close(3)                                = 0

not a whole lot of difference to be seen, there. Whether the destination file is on a local disk or an NFS mount, the write() call will be the same. The oft-named Nightmare File System will - all other things being equal - fail more often than your local disk.

You can't print because sys.stdout is not available when not running as a console session.

Instead of using print statements you can consider using the logging module so you can set the loglevel and write all critical things to the system event log.

It should be noted that you can still get it to work (or silently ignore the problem) by doing something like this:

To write to a file per output stream:

import sys
sys.stdout = open('stdout.txt', 'w')
sys.stderr = open('stderr.txt', 'w')

To write to a single file:

import sys
sys.stdout = sys.stderr = open('output.txt', 'w')

Or to silently ignore all print statements:

import sys
class NullWriter(object):
    def write(self, value): pass

sys.stdout = sys.stderr = NullWriter()

os.path.isfile() takes a file path (a string), not a file descriptor (a number), so your solution will not work as you expect.

You can use os.isatty() instead:

if os.isatty(1):
    print "text"

os.isatty() will return True if its argument is an open file descriptor connected to a terminal.

(In passing, note that stdout is file descriptor 1. stderr is file descriptor 2).