howto to do bi directionnal python + tcl/tk without tkinter

wall_clock_2.py

#!/usr/bin/env python
from subprocess import Popen, PIPE
from time import sleep, time, localtime
import fcntl
import os

# let's talk to tk/tcl directly through p.stdin
p = Popen(['wish'], stdin=PIPE, stdout=PIPE)

fd = p.stdout.fileno()
flag = fcntl.fcntl(fd, fcntl.F_GETFL)
fcntl.fcntl(fd, fcntl.F_SETFL, flag | os.O_NONBLOCK)

def puts(s):
    for l in s.split("\n"):
        p.stdin.write((l + "\n").encode())
        p.stdin.flush()

def gets():
    ret=p.stdout.read()
    p.stdout.flush()
    return ret

WIDTH=HEIGHT=400

puts(f"""
canvas .c -width {WIDTH} -height {HEIGHT} -bg white
pack .c
. configure -background white

ttk::button  .ba -command {{  puts ch-=1 }} -text <<
pack .ba -side left   -anchor w
ttk::button .bb -command {{  puts cm-=1 }} -text < 
pack .bb -side left -anchor w
ttk::button .bc -command {{  puts ch+=1 }} -text >> 
pack .bc  -side right -anchor e
ttk::button .bd -command {{  puts cm+=1 }} -text > 
pack .bd  -side right -anchor e
""")

# Constant are CAPitalized in python by convention
from cmath import  pi as PI, e as E
ORIG=complex(WIDTH/2, HEIGHT/2)

# correcting python notations j => I  
I = complex("j")
rad_per_sec = 2.0 * PI /60.0
rad_per_min = rad_per_sec / 60
rad_per_hour = rad_per_min / 12

origin_vector_hand = WIDTH/2 *  I

size_of_sec_hand = .9
size_of_min_hand = .8
size_of_hour_hand = .65

rot_sec = lambda sec : -E ** (I * sec * rad_per_sec )
rot_min = lambda min : -E ** (I *  min * rad_per_min )
rot_hour = lambda hour : -E ** (I * hour * rad_per_hour )

to_real = lambda c1,c2 : "%f %f %f %f" % (c1.real,c1.imag,c2.real, c2.imag)
for n in range(60):
    direction= origin_vector_hand * rot_sec(n)
    start=.9 if n%5 else .85
    puts(f".c create line {to_real(ORIG+start*direction,ORIG+.95*direction)}")
    sleep(.01)

diff_offset_in_sec = (time() % (24*3600)) - \
    localtime()[3]*3600 -localtime()[4] * 60.0 \
    - localtime()[5] 
ch=cm=0
while True:
    # eventually parsing tcl output 
    back = gets()
    # trying is more concise than checking
    try:
        back = back.decode()
        exec(back)
    except Exception as e:
        pass

    t = time()
    s= t%60
    m = m_in_sec = t%(60 * 60) + cm * 60
    h = h_in_sec = (t- diff_offset_in_sec)%(24*60*60) + ch * 3600 + cm * 60
    puts(".c delete second")
    puts(".c delete minute")
    puts(".c delete hour")
    c0=ORIG+ -.1 * origin_vector_hand * rot_sec(s)
    c1=ORIG+ size_of_sec_hand * origin_vector_hand * rot_sec(s)
    puts( f".c create line {to_real(c0,c1)} -tag second -fill blue -smooth true")
    c1=ORIG+size_of_min_hand * origin_vector_hand * rot_min(m)
    puts(f".c create line {to_real(ORIG, c1)} -tag minute -fill green -smooth true")
    c1=ORIG+size_of_hour_hand * origin_vector_hand * rot_hour(h)
    puts(f".c create line {to_real(ORIG,c1)} -tag hour -fill red -smooth true")
    puts("flush stdout")
    sleep(.1)