Could you please provide more details on why do we use t-test instead of z-test? How we can make a z-test in python to compare the results? Thank you in advance!

True. In this case, there are 2 reason 1) the package that is used and 2) the larger the observations, the results between t-test and z-test is closer. You can try statsmodels package for z-test

t-test is used when the sample size is less than 30

but it is not our case this time, right? in this example we have more than 30 observations