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.