Python Serial How to use the read or readline function to read more than 1 character at a time

Question

I m having trouble to read more than one character using my program  I can t seem to figure out what went wrong with my program   import serial  ser   serial Serial      port  COM5        baudrate 9600       parity serial PARITY NONE       stopbits serial STOPBITS ONE       bytesize serial EIGHTBITS           timeout 0   print  connected to      ser portstr  count 1  while True      for line in ser read             print str count    str         chr line            count   count 1  ser close     here are the results I get  connected to  COM5 1  1 2  2 3  4 4  3 5  1   actually I was expecting this  connected to  COM5 1 12431 2 12431   something like the above mentioned which is able read multiple characters at the same time not one by one

User · Answer

I was reciving some date from my arduino uno  0-1023 numbers   Using code from 1337holiday  jwygralak67 and some tips from other sources   import serial import time  ser   serial Serial      port  COM4        baudrate 9600       parity serial PARITY NONE       stopbits serial STOPBITS ONE       bytesize serial EIGHTBITS           timeout 0   print  connected to      ser portstr    this will store the line seq      count   1  while True      for c in ser read            seq append chr c    convert from ANSII         joined seq      join str v  for v in seq   Make a string from array          if chr c       n               print  Line     str count           joined seq              seq                  count    1             break   ser close

User · Answer

I use this small method to read Arduino serial monitor with Python  import serial ser   serial Serial  COM11   9600  while True       cc str ser readline         print cc 2    -5

User · Answer

I see a couple of issues   First   ser read   is only going to return 1 byte at a time   If you specify a count  ser read 5    it will read 5 bytes   less if timeout occurrs before 5 bytes arrive    If you know that your input is always properly terminated with EOL characters   better way is to use  ser readline     That will continue to read characters until an EOL is received   Second   Even if you get ser read   or ser readline   to return multiple bytes  since you are iterating over the return value  you will still be handling it one byte at a time   Get rid of the  for line in ser read      and just say   line   ser readline

User · Answer

Serial sends data 8 bits at a time  that translates to 1 byte and 1 byte means 1 character    You need to implement your own method that can read characters into a buffer until some sentinel is reached  The convention is to send a message like 12431 n indicating one line    So what you need to do is to implement a buffer that will store X number of characters and as soon as you reach that  n  perform your operation on the line and proceed to read the next line into the buffer   Note you will have to take care of buffer overflow cases i e  when a line is received that is longer than your buffer etc     EDIT  import serial  ser   serial Serial      port  COM5        baudrate 9600       parity serial PARITY NONE       stopbits serial STOPBITS ONE       bytesize serial EIGHTBITS           timeout 0   print  connected to      ser portstr    this will store the line line       while True      for c in ser read            line append c          if c      n               print  Line         join line               line                  break  ser close

[python] Python Serial: How to use the read or readline function to read more than 1 character at a time

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