Active Cooling soft PWM follow-on fan motor speed controller driver

Code:
#!/usr/bin/python

#

# fan_motor.sh

#*****************************************************************

#  author:     Mark H. Harris       

# license:     GPLv3

#

#   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND

#   CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,

#   INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

#   MECHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

#   DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR

#   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

#   SPECIAL, EXEMPLARY, OR CONSEQUENCIAL DAMAGES (INCLUDING, BUT

#   NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

#   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERUPTION)

#   HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

#   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

#   OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE

#   EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#

#*****************************************************************

## Import the necessary header modules

from time import sleep

import signal as SIGNAL

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)



## SOFTWARE PWM GPIO23 pin(16)

soft_pwm = 23

GPIO.setup(soft_pwm, GPIO.OUT)



ms_on = .016

ms_off = .004

hup_flag = False



## FUNCTION DEFINITIONS



def motor_duty_on(m_pin, t_delay):

    GPIO.output(m_pin, True)

    sleep(t_delay)

    

def motor_duty_off(m_pin, t_delay):

    GPIO.output(m_pin, False)

    sleep(t_delay)



def end():

    GPIO.cleanup()

    quit()



def ssighup(signum, frame):

    global hup_flag

    global ms_on

    global ms_off

    if (hup_flag):

        ms_on = .016

        hup_flag=False

    else:

        ms_on = .250

        hup_flag=True

    print(" ")

    print("HUP: duty_cycle toggled value: "+str(ms_on))



SIGNAL.signal(SIGNAL.SIGHUP, ssighup)



kb_interrupt = False



while(not kb_interrupt):

    try:

        motor_duty_on(soft_pwm, ms_on)

        motor_duty_off(soft_pwm, ms_off)

    except KeyboardInterrupt:

        kb_interrupt = True

        print(" ")

        print("motor controller ended by interrupt, bye!")



end()