Frame objects
Frame objects represent execution frames. They may occur in traceback objects (see below).
f_lasti gives the precise instruction (this is an index into the bytecode string of the code object).
f_lineno is the current line number of the frame — writing to this from within a trace function jumps to the given line (only for the bottom-most frame). A debugger can implement a Jump command (aka Set Next Statement) by writing to f_lineno.
Traceback objects
sys.last_traceback.
try statement with no matching except clause or with a finally clause.