I'm using the following code to hide stderr on Linux/OSX for a Python library I do not control that writes to stderr by default:
f = open("/dev/null","w")
zookeeper.set_log_stream(f)
Is there an easy cross platform alternative to /dev/null? Ideally it would not consume memory since this is a long running process.
How about os.devnull ?
import os
f = open(os.devnull,"w")
zookeeper.set_log_stream(f)
os.devnull also works for with open() blocks, where the 'file-like object' solution throws: TypeError: expected str, bytes or os.PathLike, not Devnullclass Devnull(object):
def write(self, *_): pass
zookeeper.set_log_stream(Devnull())
Opening os.devnull is fine too of course, but this way every output operation occurs (as a noop) "in process" -- no context switch to the OS and back, and also no buffering (while some buffering is normally used by an open) and thus even less memory consumption.
write of its log_stream file object? Maybe it calls the writelines method? Then there is an exception.
fileno().
os.open(os.devnull, os.O_RDWR) and yielding the same fd for subsequent calls to fileno (since all data are discarded anyway)
close()
io.IOBase and just overwrite write() as above do the trick? That would provide all the methods clients might expect.>>> import os
>>> os.devnull
'nul'
Create your own file-like object which doesn't do anything?
class FakeSink(object):
def write(self, *args):
pass
def writelines(self, *args):
pass
def close(self, *args):
pass
args. As we don't use any of the parameters, the only reason to care is aesthetic. I'll fix it...
Cheap solution warning!
class DevNull():
def __init__(self, *args):
self.closed = False
self.mode = "w"
self.name = "<null>"
self.encoding = None
self.errors = None
self.newlines = None
self.softspace = 0
def close(self):
self.closed == True
@open_files_only
def flush(self):
pass
@open_files_only
def next(self):
raise IOError("Invalid operation")
@open_files_only
def read(size = 0):
raise IOError("Invalid operation")
@open_files_only
def readline(self):
raise IOError("Invalid operation")
@open_files_only
def readlines(self):
raise IOError("Invalid operation")
@open_files_only
def xreadlines(self):
raise IOError("Invalid operation")
@open_files_only
def seek(self):
raise IOError("Invalid operation")
@open_files_only
def tell(self):
return 0
@open_files_only
def truncate(self):
pass
@open_files_only
def write(self):
pass
@open_files_only
def writelines(self):
pass
def open_files_only(fun):
def wrapper(self, *args):
if self.closed:
raise IOError("File is closed")
else:
fun(self, *args)
return wrapper
Use builtin len that would also return amount of bytes "written" (as expected from write):
import types
f = types.SimpleNamespace(write=len)
zookeeper.set_log_stream(f)
open(os.devnull)according to user stackoverflow.com/a/13944391/5267751 ■ if you want to redirect stdout there's a special solution stackoverflow.com/a/47419332/5267751