Generating a UUID per invocation?

[Anti-Distinctlyminty]

Hi,
I have some code to setup and teardown a database for each run that I put into commands_pre and commands_post respectively. However, if I want to do a parallel run I cannot have a static database name. What I need to do is create an UUID environment variable to use as a database name (with no - character otherwise I'd use {envname}), however I cannot find a way to do this.

What I'm currently trying is something like this below (I also need to load an env file hence the use of python-dotenv[cli]

commands_pre = 
    ; Somehow set environment variable DB?
    dotenv -f {toxinidir}{/}sensitive.env run "{env:PSQL_EXE}" -c "DROP DATABASE IF EXISTS %DB%"
commands =
    pytest
commands_post = 
    dotenv -f {toxinidir}{/}sensitive.env run "{env:PSQL_EXE}" -c "DROP DATABASE %DB%"

But this doesn't work as I don't think %DB% is expanded (I tried something like dotenv -f {toxinidir}{/}sensitive.env run "SET DB=something && {env:PSQL_EXE}" -c "DROP DATABASE IF EXISTS %DB%" with no luck.

Is there a away tox can support this?

[jugmac00]

While this may work via tox, usually you do this in your test code, e.g. in a pytest fixture which does setup and teardown (after the yield keyword).

[Anti-Distinctlyminty]

I did have that, but moved it from pytest to tox. The reason for this is I needed the database to be setup before pytest was called, as I have some fixtures that are parameterized using information from the database.

[jugmac00]

Ok - you may have reasons, but this sounds against all odds. Usually you do not want to have test data in a database, but rather have Python factories which create the test data.

Given you have good reasons or you do not care :-), here is a solution for your current problem:

tox.ini

[testenv]
whitelist_externals = bash
commands = bash run.sh

run.sh

UUID=$(uuidgen)
# do stuff with UUID
pytest
# do some more stuff with UUID
echo $UUID

[Anti-Distinctlyminty]

I'm on Windows, but I'll see if I can make a bat file or powershell script to do the same.
One question: the commands that are listed in commands_pre, commands and commands_post - are they completely independent from one another, or will environment variables created on one line persist?

[jugmac00]

Tbh, I don't know.

You could set a variable in commands_pre and print/echo it in the others.

https://superuser.com/questions/79612/setting-and-getting-windows-environment-variables-from-the-command-prompt/79614

[Anti-Distinctlyminty]

@jugmac00 I found a perfect solution: tox-backticks. This allowed me to do this

[tox]
requires = tox-backticks

commands_pre = 
    dotenv -f {toxinidir}{/}sensitive.env run "{env:PSQL_EXE}" -c "DROP DATABASE IF EXISTS {env:TEST_DB}"
commands =
    pytest
commands_post = 
    dotenv -f {toxinidir}{/}sensitive.env run "{env:PSQL_EXE}" -c "DROP DATABASE{env:TEST_DB}"
setenv = 
    TEST_DB=`python -c 'import sys; sys.stdout.write("{envname}".replace("-", ""))'`

I used the envname with the "-" removed as a UUID.
Thanks for the rubber ducking!