Description
Python file method flush[] flushes the internal buffer, like stdio's fflush. This may be a no-op on some file-like objects.
Python automatically flushes the files when closing them. But you may want to flush the data before closing any file.
Syntax
Following is the syntax for flush[] method −
fileObject.flush[];
Parameters
NA
Return Value
This method does not return any value.
Example
The following example shows the usage of flush[] method.
#!/usr/bin/python # Open a file fo = open["foo.txt", "wb"] print "Name of the file: ", fo.name # Here it does nothing, but you can call it with read operation. fo.flush[] # Close opend file fo.close[]
When we run above program, it produces following result −
Name of the file: foo.txt
python_files_io.htm
- How often does Python flush to a file?
- How often does Python flush to stdout?
I'm unsure about [1].
As for [2], I believe Python flushes to stdout after every new line. But, if you overload stdout to be to a file, does it flush as often?
asked Jul 2, 2010 at 16:30
Tim McJiltonTim McJilton
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0
For file operations, Python uses the operating system's default buffering unless you configure it do otherwise. You can specify a buffer size, unbuffered, or line buffered.
For example, the open function takes a buffer size argument.
//docs.python.org/library/functions.html#open
"The optional buffering argument specifies the file’s desired buffer size:"
- 0 means unbuffered,
- 1 means line buffered,
- any other positive value means use a buffer of [approximately] that size.
- A negative buffering means to use the system default, which is usually line buffered for tty devices and fully buffered for other files.
- If omitted, the system default is used.
code:
bufsize = 0
f = open['file.txt', 'w', buffering=bufsize]
zyxue
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answered Jul 2, 2010 at 19:02
Corey GoldbergCorey Goldberg
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You can also force flush the buffer to a file programmatically with the
flush[]
method.
with open['out.log', 'w+'] as f:
f.write['output is ']
# some work
s = 'OK.'
f.write[s]
f.write['\n']
f.flush[]
# some other work
f.write['done\n']
f.flush[]
I have found this useful when tailing an output file with tail -f
.
Martin Thoma
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answered Mar 10, 2011 at 5:13
6
I don't know if this applies to python as well, but I think it depends on the operating system that you are running.
On Linux for example, output to terminal flushes the buffer on a newline, whereas for output to files it only flushes when the buffer is full [by default]. This is because it is more efficient to flush the buffer fewer times, and the user is less likely to notice if the output is not flushed on a newline in a file.
You might be able to auto-flush the output if that is what you need.
EDIT: I think you would auto-flush in python this way [based from here]
#0 means there is no buffer, so all output
#will be auto-flushed
fsock = open['out.log', 'w', 0]
sys.stdout = fsock
#do whatever
fsock.close[]
answered Jul 2, 2010 at 16:37
KLee1KLee1
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You can also check the default buffer size by calling the read only DEFAULT_BUFFER_SIZE attribute from io module.
import io
print [io.DEFAULT_BUFFER_SIZE]
answered May 20, 2016 at 15:28
N RandhawaN Randhawa
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1
Here is another approach, up to the OP to choose which one he prefers.
When including the code below in the __init__
.py file
before any other code, messages printed with print
and any errors will no longer be logged to Ableton's Log.txt but to separate files on your disk:
import sys
path = "/Users/#username#"
errorLog = open[path + "/stderr.txt", "w", 1]
errorLog.write["---Starting Error Log---\n"]
sys.stderr = errorLog
stdoutLog = open[path + "/stdout.txt", "w", 1]
stdoutLog.write["---Starting Standard Out Log---\n"]
sys.stdout = stdoutLog
[for Mac, change #username#
to the name of your user folder. On Windows the path to your user folder will have a different format]
When you open the files in a text editor that refreshes its content when the file on disk is changed [example for Mac: TextEdit does not but TextWrangler does], you will see the logs being updated in real-time.
Credits: this code was copied mostly from the liveAPI control surface scripts by Nathan Ramella
answered Jul 29, 2016 at 9:09
MattijsMattijs
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