I need help with a python script I am trying to adapt for a specific need

I am a total newbie with Python, I normally use Perl.

I have an Arduino wired up with some servos I use to control a web cam, the script in question works perfect, the servos receive the instruction and do what they should:

    #!/usr/bin/env python
    import serial

    usbport = '/dev/ttyACM0'

    # Set up serial baud rate
    ser = serial.Serial(usbport, 9600, timeout=1)


    def move(servo, angle):
        '''Moves the specified servo to the supplied angle.

        Arguments:
        servo
          the servo number to command, an integer from 1-4
        angle
         the desired servo angle, an integer from 0 to 180

    (e.g.) >>> servo.move(2, 90)
           ... # "move servo #2 to 90 degrees"'''

    if (0 <= angle <= 180):
       ser.write(chr(255))
       ser.write(chr(servo))
       ser.write(chr(angle))
    else:
        print "Servo angle must be an integer between 0 and 180.\n"

Basically the command for the above script is:

    python
    import servo
    servo.move(1, 180)

I have converted the script to accept command line input, however the program does not seem to work. can anyone figure out what I am doing wrong, here is my version:

    #!/usr/bin/env python
    import serial
    import sys

    try:
            servo = int(sys.argv[1])
            angle = int(sys.argv[2])
    except IndexError:
            print ('a servo and angle are required')
    sys.exit(2)

    # Set up serial baud rate
    usbport = '/dev/ttyACM0'
    ser = serial.Serial(usbport, 9600, timeout=1)

    def move(servo, angle):
        '''Moves the specified servo to the supplied angle.

    Arguments:
        servo
          the servo number to command, an integer from 1-4
        angle
          the desired servo angle, an integer from 0 to 180

    (e.g.) >>> servo.move(2, 90)
           ... # "move servo #2 to 90 degrees"'''

    if (0 <= angle <= 180):
        ser.write(chr(255))
        ser.write(chr(servo))
        ser.write(chr(angle))
    else:
        print "Servo angle must be an integer between 0 and 180. You typed:"
        print servo
  开发者_开发问答      print angle
    move(servo, angle)

Basically the command for the above script is:

    servo.py 1 180

I know the script works as it should as if I tell it to do a 1 181 I get the error that the angle is out of range, so I'm totally puzzled as to why the info is not passed to the serial/arduino.

Many thanks for any help and sorry for the long winded post.

Gilbert

---

Beside @combatdave's answer, on this part:

try:
        servo = int(sys.argv[1])
        angle = int(sys.argv[2])
except IndexError:
        print ('a servo and angle are required')
sys.exit(2)

# Set up serial baud rate

You should indend sys.exit(2) too. Because of this, the program exits right after getting arguments.

---

It looks like your indentation after the function definition is wrong. It should be:

def move(servo, angle):
    '''Moves the specified servo to the supplied angle.

    Arguments:
        servo
          the servo number to command, an integer from 1-4
        angle
          the desired servo angle, an integer from 0 to 180

    (e.g.) >>> servo.move(2, 90)
           ... # "move servo #2 to 90 degrees"'''

    if (0 <= angle <= 180):
        ser.write(chr(255))
        ser.write(chr(servo))
        ser.write(chr(angle))
    else:
        print "Servo angle must be an integer between 0 and 180. You typed:"
        print servo
        print angle

(Note how the if...else block is indented)

---

Why adapt the original script? Just use this:

import servo
servo.move(int(argv[1]), int(argv[2]))

I'm not sure whether this happened when pasting code into stackoverflow, but the indenting is flawed on multiple places. Please check this too :)

---

Your indentation is wrong basically.

See this snippet:

try:
        servo = int(sys.argv[1])
        angle = int(sys.argv[2])
except IndexError:
        print ('a servo and angle are required')
sys.exit(2)

The sys.exit(2) call is always executed! So the program does nothing.