How often does python flush to a file

Question

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

User · Accepted Answer

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   http   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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

[python] How often does python flush to a file?

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