The following code, when traced, produces a spurious line event for line 5:

a, b, c = 1, 1, 1
try:
    a = 3
except:
    b = 5
finally:
    c = 7
assert a == 3 and b == 1 and c == 7

Bug reported by Ned Batchelder https://gist.github.com/nedbat/6c5dedde9df8d2de13de8a6a39a5f112

I checked on this with CPython commit c95f8bc270.  The code above is fixed, but this code has a similar problem:

a, b, c = 1, 1, 1
try:
    try:
        a = 4/0         # ZeroDivisionError
    except ValueError:
        b = 6
    except IndexError:
        a = 8           # Line 8
    finally:
        c = 10
except ZeroDivisionError:
    pass
assert a == 1 and b == 1 and c == 10


Using a simple trace program (https://github.com/nedbat/coveragepy/blob/master/lab/run_trace.py), it produces this output:

call <string> 1 @-1
    line <string> 1 @0
    line <string> 2 @10
    line <string> 3 @12
    line <string> 4 @16
    exception <string> 4 @20
    line <string> 5 @28
    line <string> 7 @48
    line <string> 8 @68
    line <string> 10 @78
    line <string> 11 @88
    line <string> 12 @100
    line <string> 13 @106
    return <string> 13 @136

Line 8 should never be executed.

(Rather: line 8 isn't executed, and so should not be traced.)

New changeset f2dbfd7e20431f0bcf2b655aa876afec7fe03c6f by Mark Shannon in branch 'master':
bpo-42634: Mark reraise after except blocks as artificial. (GH-23877)
https://github.com/python/cpython/commit/f2dbfd7e20431f0bcf2b655aa876afec7fe03c6f

Friendly reminder that this issue is currently blocking the 3.10a5 release. If you are ok with waiting for the next release to include the fix, please say so here or drop me an email/

This problem no longer appears with master (commit 9eb11a139f).

Sorry. I forgot the close the issue when it was fixed.