Renaming a variable in a Python code in MS VS Code

I have defined a variable T_0 at the top of a python code, and want to change this variable by F2 of MS VS Code.

T_0 = 10
T_1 = T_0 + 1
print(T_1)

But first, I got an error message Refactoring library rope is not installed.

Then I found an answer to this at here. After appropriately changed this, I got a new error message Refactor failed. Rename refactoring should be performed on resolvable python identifiers..

How can I rename a variable in a python code on MS VS Code?

I am using Python 3.6, VS Code 1.19.2.