It was weird as my code with global vars works in VS Code but did not pass tests online. Can you recommend a good article to read how to use global vars correctly? Thanks.

I don't see "don't use global variables" in the instructions... May the instructions should be updated?

This solution is for old kata without parenthesis.

I tried to run old solutions and they fall if sting has parenthesis. I think kata's Sensei obrok would start a new kata instead for new tests with parenthesis.

In VS Code Python 3.9.4 Win 10:

Calculator().evaluate("( ( ( ( 1 ) * 2 ) ) )")
return float(str_list[0])
ValueError: could not convert string to float: '('

Not working for me in VS Code Python 3.9.4 Win 10:

Calculator().evaluate("3 * ( 4 + 7 ) - 6")
self.result[i - 1] = str(self.operands[x](float(self.result[i-1]), float(self.result[i + 1])))
ValueError: could not convert string to float: '('

cheater :D

Now I see my misstake :-) Thanks!