The VPE and other logs¶
If you do any non-trivial Python scripting within Vim, it is verly likely that
you will find it helpful to be able to write log message. Python programmers
often simply use calls to print() for this and this can be useful from
within Vim. However, such output will typicall cause the Vim window to scroll
and wait for the user to press a key. This can be inconvenient during Python
scripting development.
A simple way to work around this is to open a file and write to that instead. The log file can be loaded into to Vim and, perhaps, its ‘autoread’ option be set.
VPE provides an additional way to support scripting logging. The vpe.log
object.
The vpe.log¶
This acts as a simple alternative to the print() function that directs its
output to a Vim buffer.
from vpe import log
log('This will go to the VPE log buffer.')
The easiest way to make the VPE log buffer visible is to use Log.show.
# Make the log buffer visible in a split window.
log.show()
The log buffer has some special behaviours.
The text in the log buffer is shown with a simple time stamp of seconds and hundreths of a second.
The number of lines in the buffer is limited. When the limit is reached, older lines are deleted. The default length is 500 lines, but this can be changed using the
Log.set_maxlenmethod.When the log buffer is being shown in a window, it is automatically scrolled to show new output as it gets written.
You can also redirect sys.stdout and sys.stderr to the VPE log.
# Make all future printing go to the VPE log. This also redirects
# sys.stderr.
log.redirect()
...
# Undo effect of the last call to redirect.
log.unredirect()
I personally find it convenient to always have redirection enabled, which I do in my personal Vim initialisation scripts. I also have a key mapping to make it easy to quickly view the log.
:nmap <S-F1> :py3 vpe.log.show()<cr>
Error logging¶
When VPE traps an error condition, it will normally write one or more error
messages to the vpe.log. This is typically less disruptive that writing to
the Vim console.
Currently the log output does not distinguish between normal output and errors. This may well change in the future.
Other logs¶
The vpe.log object is actualy just a specific instance of the vpe.Log
class. VPE only creates the vpe.log automatically, but it can be more useful
to create your own Log for your script or plug-in. This keeps your plug-in’s
log output nicely separate.