<p>I am using python 3.6 with pySerial library to connect to the Hyrel System 30M 3D Printer. I am able to read the data from the device but unable to write any commands to it</p>

<p>Here is the code:</p>



<pre><code>    ser = serial.Serial()
    ser.port = 'COM4'
    ser.baudrate = 38400
    out = ser.readline()
    ser.write(b'M106 T14 S30\n') %This is the command to turn on the fan at 30% power
</code></pre>

<p>Can somebody suggest me how to write commands to printer through python</p>

If the one in your question is your
complete
code, a possibility is that your computer is just buffering the output for the serial port, withholding it in memory.  Try to add
```
```
ser.flush()
```
```
after your last line.  This command will... well...
flush
anything into the buffer through the actual connection.