Hello!

I'm on Windows, using Python3 from Anaconda distrib. I've set option

 '(python-shell-interpreter "py")

When doing

M-x run-python

I get

Warning (python): Your ‘python-shell-interpreter’ doesn’t seem to support readline, yet ‘python-shell-completion-native-enable’ was t and "py" is not part of the ‘python-shell-completion-native-disabled-interpreters’ list.  Native completions have been disabled locally. 

Python 3.6.1 |Anaconda 4.4.0 (64-bit)| (default, May 11 2017, 13:25:24) [MSC v.1900 64 bit (AMD64)] on win32

Type "help", "copyright", "credits" or "license" for more information.

>>> python.el: native completion setup failed

>>>

It is expected that Python completion works out-of-the-box, without warnings.

Ready to provide any additional info,

Andrey Paramonov

In GNU Emacs 25.3.1 (x86_64-w64-mingw32)

 of 2017-09-17 built on LAPHROAIG

Windowing system distributor 'Microsoft Corp.', version 6.3.9600

Configured using:

 'configure --without-dbus --without-compress-install 'CFLAGS=-O2

 -static -g3''

Configured features:

XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY ACL GNUTLS LIBXML2 ZLIB

TOOLKIT_SCROLL_BARS

Important settings:

  value of $LANG: RUS

  locale-coding-system: cp1252

Major mode: Special

Minor modes in effect:

  shell-dirtrack-mode: t

  tooltip-mode: t

  global-eldoc-mode: t

  electric-indent-mode: t

  mouse-wheel-mode: t

  tool-bar-mode: t

  menu-bar-mode: t

  file-name-shadow-mode: t

  global-font-lock-mode: t

  font-lock-mode: t

  auto-composition-mode: t

  auto-encryption-mode: t

  auto-compression-mode: t

  buffer-read-only: t

  line-number-mode: t

  transient-mark-mode: t

Recent messages:

For information about GNU Emacs and the GNU system, type C-h C-a.

Making completion list...

You can run the command    run-python    with C-c C-p

Shell native completion is disabled, using fallback

Load-path shadows:

None found.

Features:

(shadow sort mail-extr thingatpt emacsbug message dired rfc822 mml

mml-sec epg mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev

gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mail-utils

warnings compile tramp-cache python tramp-sh tramp tramp-compat

auth-source cl-seq eieio eieio-core cl-macs gnus-util mm-util help-fns

mail-prsvr password-cache tramp-loaddefs trampver ucs-normalize shell

pcomplete format-spec advice json map comint ring ansi-color finder-inf

info tex-site package epg-config seq byte-opt gv bytecomp byte-compile

cl-extra help-mode easymenu cconv cl-loaddefs pcase cl-lib time-date

mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks

lisp-float-type mwheel dos-w32 ls-lisp disp-table w32-win w32-vars

term/common-win tool-bar dnd fontset image regexp-opt fringe

tabulated-list newcomment elisp-mode lisp-mode prog-mode register page

menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock font-lock

syntax facemenu font-core frame cl-generic cham georgian utf-8-lang

misc-lang vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms

cp51932 hebrew greek romanian slovak czech european ethiopic indian

cyrillic chinese charscript case-table epa-hook jka-cmpr-hook help

simple abbrev minibuffer cl-preloaded nadvice loaddefs button faces

cus-face macroexp files text-properties overlay sha1 md5 base64 format

env code-pages mule custom widget hashtable-print-readable backquote

w32notify w32 multi-tty make-network-process emacs)

Memory information:

((conses 16 238322 10475)

 (symbols 56 24227 0)

 (miscs 48 129 150)

 (strings 32 31786 7274)

 (string-bytes 1 989742)

 (vectors 16 40361)

 (vector-slots 8 734537 6096)

 (floats 8 256 140)

 (intervals 56 426 0)

 (buffers 976 24))