Convert string to float problem

[vasik006]

Hi, I have a problem converting a string to a float. The program receives data from Arduino via the serial port and processes it. But I'm getting this error message. Is there a solution? Thank you!

from pynput.mouse import Button, Controller
import time
import serial

mouse = Controller()
ser = serial.Serial('COM3', baudrate=9600, timeout=1)


while True:
    arduinoData = ser.readline().decode('ascii')
    print(arduinoData)
    data = (float(arduinoData))
    mouse.position = (data, 100)

[ndc85430]

The string is empty. What should your program do in that case? You can catch the exception and set whatever value you want when that happens, or do something else.

[deanhystad]

If you don't get get data within 1 second the read gives up and returns an empty buffer. It is possible that you could also time out while reading data and get a partial buffer. You might also get a transmission error that results in bad data. I would cover all three possibilities by wrapping an exception handler around the conversion and only updating the mouse position when you successfully read a new value.

[vasik006]

Arduino sends data with a delay of 1 ms.

[vasik006]

This is how output and Arduino code looks like.

[vasik006]

Oh, thank you. It works perfectly with try/except! Also I have one more question. I need to make value bigger (multiply), but this does not work. How can I do it?

from pynput.mouse import Button, Controller
import time
import serial

mouse = Controller()
ser = serial.Serial('COM3', baudrate=9600, timeout=1)


while True:
    try:
        arduinoData = ser.readline().decode('ascii')
        data = (arduinoData)/5
        print(data)
        mouse.position = (data, 100)
    except:
        print("fail")
        break

EDIT: Solved also this.

[deanhystad]

Where is float()?

[vasik006]

Where is float()?

Program doesnt end with error anymore so I don´t need it.

[deanhystad]

This gets a str object:

arduinoData = ser.readline().decode('ascii')

This tries to divide the str by 5

data = (arduinoData)/5

Dividing a str by an int raises a TypeError which is caught by the overly broad except: Your program prints "fail" every time, no matter what is read
You should do this:

data = float(arduinoData)/5

This might also fail, but if arduinoData is a string that can be interpreted as a float, it will succeed.