str TypeError, yes it's basic but hear me out
<p>I know, this is probably a very simple problem, but no matter how many times I go through this, this isn't making any sense. I made a very simple class that is meant for controlling an Arduino-based car. I set it up so that the serialOut function will return a string with the necessary formatting to send over serial. However, whenever I use it, I keep getting this error:</p>

<blockquote>
<pre><code>Traceback (most recent call last):
  File "&lt;pyshell#5&gt;", line 1, in &lt;module&gt;
    car.serialOut()
TypeError: 'str' object is not callable
</code></pre>
</blockquote>

<p>this is the code for the class:</p>

<pre><code># Drive Communication System
import serial

def output(speed,steer,orientation):
        return ('%02d' % speed) + ('%02d' % steer) + (orientation)

class DriveTrain:

    def __init__(self,serial,cruise_speed = 60, turn_sensitivity = 1):
        self.serialOut = '0045s'
        self._cruise = cruise_speed
        self._trim = turn_sensitivity
        self._speed = 0
        self._steer = 0
        self._orientation = 's'

    def Drive(self,speed, steer = 0, orientation = 's'):
        self._steer = steer + 45
        self._speed = speed
        self._orientation = orientation

    def stop(self):
        self._steer = 45
        self._speed = 0
        self._orientation = 's'

    def status(self):
        return (self._speed,self._steer - 45,self._orientation)

    def serialOut(self):
        return output(self._speed,self._steer,self._orientation)

if __name__ == '__main__':
    ser = serial.Serial('COM3',38400)
    car = DriveTrain(ser)
    car.Drive(60)
    #car.Drive(60)
</code></pre>

<p>Originally, I had the operations currently in the output function in the actual serialOut class function, but the same things happened. I also attached a picture that shows how I went through checking each operation, and yet for some reason it still won't work. I'm obviously missing something simple, but for the life of me, I just can't figure out what it is...</p>

<p><a href="https://i.stack.imgur.com/d8fO9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/d8fO9.png" alt="Testing the code"></a></p>