While working on bpo-45126 / GH-28227 (and while working on the AC conversion, bpo-40956), I've been slightly frustrated on the implementation of sqlite3 "isolation level". The code is messy, and we've got two connection members that carry pretty much the same type of information (self->isolation_level, and self->begin_statement).

I would like to make the following enhancements:
  - merge 'isolation_level' and 'begin_statement' members in some kind of way
  - split pysqlite_connection_set_isolation_level():
    + one method for parsing and storing the 'isolation_level' member
    + one method for carrying out any needed SQLite API operation

This should result in a cleaner connection __init__() method.


Another slightly related performance enhancement could be to cache the "begin" (and "commit") statements as sqlite3_stmt pointers on the connection object, but that is a digression.