Am 10.02.22 um 20:43 schrieb Chris Angelico:
On Fri, 11 Feb 2022 at 06:41, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
While not tested with Excel, I /have/ encountered cases where an
application has locked the file for writing, but multiple readers are
permitted. Those would fail then if one attempts to write. {The other view
point is a library that does a complete open/read\write-all/close to memory
-- such an application might open/read/close, then Excel opens/locks, with
the application only learning of the change when it attempts the
open/write/close cycle}
Yeah, I doubt Excel is that sophisticated. It's built on an assumption
of single-user operation.
It guards against multiple user opening the same file over network
drives. All MS applications create lock files with weird names like
~.original-name.xlsx etc. If you open a file on the network share, and a
colleague tries to open it from a second machine, then he will get the
message "File locked by user xy from machine z". See here for word:
https://support.microsoft.com/en-us/topic/-the-document-is-locked-for-editing-by-another-user-error-message-when-you-try-to-open-a-document-in-word-10b92aeb-2e23-25e0-9110-370af6edb638
I believe (haven't tested) that this is cooperative locking only and it
doesn't help if you alter the file from another program. On the same
machine though, I think that Excel opens the file with a flag to lock it
from other processes. At least that was my observation and also what the
OP has described.
Hence it is impossible to concurrently write from Python into an open
Excel file. One might ask what the real problem is the user is trying to
solve. Is Excel a requirement, can it be swapped by a database engine?
Best regards,
Christian
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