python - AttributeError: 'str' object has no attribute 'inWaiting' -

from of community able install al new backend matplotlib , run code arduino serial output of python window.

i able make pretty graph , displays, crashes when following error:

attributeerror: 'str' object has no attribute 'inwaiting'

this remedied of @elethan

however, have error:

pulse =  float(dataarray[0]) valueerror: not convert string float:  

this error not happen everytime

as if wasn't enough, output on plotted graph shows value of 10 of plot, not value output arduino serial.

i unsure why: 1) error intermittend (maybe grabbing ',' , not value) 2) why steady value of 10 when graph plot

the code follows:

import time import serial import matplotlib.pyplot plt import numpy drawnow import * import os,sys  pulsearray = []  plt.ion()  clippingcounter = 0  # configure serial connections (the parameters differs on device connecting to) ser = serial.serial(     port='/dev/ttyacm0',     baudrate=115200,     parity=serial.parity_odd,     stopbits=serial.stopbits_two,     bytesize=serial.sevenbits )    ser.isopen()    input=1  def plotpulsedata():      plt.ylim(0,120)     plt.title('plots data of pulse sensor')     plt.grid(true)     plt.ylabel('pulse')     #plt.subplot(2, 2, 1)     plt.plot(pulsearray, 'ro-', label='bpm', linewidth=2)     plt.legend(loc='upper left')    while true:     #first things first, lets wait data prior reading     time.sleep(1)      if (ser.inwaiting()>4):          s = ser.read(4)         #print ser          dataarray = s.split(',')         pulse =  float(dataarray[0])          pulsearray.append(pulse)          plt.figure(1)         drawnow(plotpulsedata)         plt.pause(.000001)          clippingcounter = clippingcounter + 1          if(clippingcounter>50):           pulsearray.pop(0) 

any appreciated, thank in advance.

you reassign ser first time through while loop serial object string:

ser = ser.read(4) 

the next time through loop when call inwaiting() method on object, error, because calling on string, instead of original serial object:

ser.inwaiting() > 4  

change variable name output of ser.read(4) name not taken, , error should go away:

s = ser.read(4) ... dataarray = s.split(',')