Following program shows that frame.f_code.co_firstlineno ignores first line if it is a comment (or empty line), but inspect.getsource(frame.f_code) returns also the first line:

# first line
import inspect
frame = inspect.currentframe()
print(frame.f_code.co_firstlineno)
print(inspect.findsource(frame.f_code))

Sorry, but I can't reproduce at 3.7, 3.5, or 2.7.
the result shows me that inspect does respect comment line.

➜  cpython git:(350) ✗ ./python /tmp/main.py
2
(['# First line\n', 'import inspect\n', 'frame = inspect.currentframe()\n', 'print(frame.f_code.co_firstlineno)\n', 'print(inspect.findsource(frame.f_code))\n'], 0)

➜  /tmp python2 main.py
2
(['# First line\n', 'import inspect\n', 'frame = inspect.currentframe()\n', 'print(frame.f_code.co_firstlineno)\n', 'print(inspect.findsource(frame.f_code))\n'], 0)

Looks like I misinderstood inspect.findsource. I thought it is supposed to give only the code for argument object (eg. only def code when given a function), but looks like it is giving the whole file.

Unfortunately inspect.findsource is not documented in https://docs.python.org/3/library/inspect.html and inspect.getsource can't be used as replacement, because it doesn't work with modules.