On 12/6/23 03:37, Chris Green via Python-list wrote:
Is there a neat, pythonic way to store values which are 'sometimes'
changed?
My particular case at the moment is calibration values for ADC inputs
which are set by running a calibration program and used by lots of
programs which display the values or do calculations with them.
From the program readability point of view it would be good to have a
Python module with the values in it but using a Python program to
write/update a Python module sounds a bit odd somehow.
I could simply write the values to a file (or a database) and I
suspect that this may be the best answer but it does make retrieving
the values different from getting all other (nearly) constant values.
Are there any Python modules aimed specifically at this sort of
requirement?
Another programming-term for these might be "environment variables".
However, be aware that such also has a specific meaning at the Operating
System level.
1 Sysops Environment Variables exist completely outside the code. Python
interrogates the Sysops to fetch/set them. Can be problematic because
only apply on single machine and are not part of change-control, VS, etc.
2 A .con file (in my tradition, likely still .uni type in MSFT) or
similar, which contains the key:value pairs recommended elsewhere. There
are formal .con and .uni (etc) formats. Most of the teams I've
worked-with recently seem to settle on .JSON files which are
very-conveniently structured as (read into/written from) a Python
dictionary, and a single function-call interaction.
Word of warning/voice of [bitter] experience: ALWAYS *trumpet* any
changes in these values AND output them (as you would any "assumptions"
for a calculation) at the top of output reports. The trouble is that
humans assume continuity but such an arrangement is NOT idempotent -
which leads to complaints: "I ran it on Monday and got these results,
but when I ran it again on Tuesday, the results changed"...
Yes there are Python libraries. Choose your method/format first, and
then search - either Duckboards or straight from Pepi.
I have systems which use an DBMS for environment variables, but (a) only
when there's a significant number, and (b) when the application is
already connecting to the DBMS for processing [and maybe (c) because I
know my way around such tools so they're 'easy']. Not recommended!
--
Regards =dn
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