Python Forum

Hi,

I'm following the book Beginning Robotics with Raspberry Pi & Arduino.

I'm familiar with the Arduino and C++, but learning Python along with the book.

I'm at the part where I'm sending Distance Measurements from an Arduino hooked up to an HC-SR04 sensor over the USB serial connection to be displayed by the Python program.

This is the code that I have

# Import serial and time libraries
import serial
import time

ser = serial.Serial('/dev/ttyACM0',9600,timeout=1)

while 1:
        recSer = ser.readline().decode('utf-8')
        recSer.rstrip()
        distance = int(recSer + '0')/10
        print("Distance: " + str(distance) + "cm", end = '\r')
        time.sleep(0.5)

Here is the error:

Error:
Distance: 0.0cm
Traceback (most recent call last):
  File "/home/bkmypie/Documents/Robotics-Pie-Arduino/serial_test.py", line 10, in <module>
    distance = int(recSer + '0')/10
ValueError: invalid literal for int() with base 10: '342\r\n0

I have googled around the net and I understand it is to with trying to display a float as an int in a string, but I'm at a loss on how to fix it.

I've tried int(float(recSer + '0') but still no joy.

I am using Python 3.5.3 on the Raspberry Pi,

Any help appreciated,

(May-18-2019, 06:30 PM)VostokRising Wrote: [ -> ]recSer.rstrip()
distance = int(recSer + '0')/10

rstrip() does not work in-place
so it should be

recSer = recSer.rstrip()

then what is the point to conacatenate 0 and then devide by 10? convert to float? then simply use float()
if it is just for string formatting

Python 3.7.3 (default, Mar 26 2019, 01:59:45) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> recSer = '342\r\n'  # to replicate what you get
>>> distance = recSer.rstrip()
>>> float(distance)
342.0
>>> distance = int(distance) # convert from str to int
>>> print(f'Distance is {distance:.1f}cm')
Distance is 342.0cm

Hi buran,

Thanks for that. It works perfectly. Like I said I'm working through the book and wrote down his code as he has it in the chapter.