Why are these files names started with underscore?

[gmspro]

Hi, 

I see there are some files here started with underscore(_) , is there any convention of something for it?

http://hg.python.org/cpython/file/3b7230997425/Modules

_bisectmodule.c
_bz2module.c
_codecsmodule.c
_collectionsmodule.c
_cryptmodule.c
_csv.c
_curses_panel.c
_cursesmodule.c
_datetimemodule.c
_dbmmodule.c
_elementtree.c
_freeze_importlib.c
_functoolsmodule.c
_gdbmmodule.c
_gestalt.c
_hashopenssl.c
_heapqmodule.c
_json.c
_localemodule.c
_lsprof.c
_lzmamodule.c
_math.c
_math.h
_pickle.c
_posixsubprocess.c
_randommodule.c
_scproxy.c
_sre.c
_ssl.c
_ssl_data.h
_struct.c
_testbuffer.c
_testcapimodule.c
_testembed.c
_threadmodule.c
_tkinter.c
_weakref.c
_winapi.c

Is there any convention or something?

Any answer will be highly appreciated.

Thanks.


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