What is difference between pymodbus and pymodbus3 modules?

Hope you are doing great! I recently started using python for modbus communication. I want to clear my few doubts.

1. What module is better for modbus implementation using Python - minimalmodbus, pymodbus, pymodbus3 or else.
2. I am using python3.4 but unable to install pymodbus module using pip or any means. So I installed pymodbus3.

3. While using pymodbus3 module, I was able to write coils using following code:

   import pymodbus3
   import serial
   from pymodbus3.pdu import ModbusRequest
   from pymodbus3.client.sync import ModbusSerialClient as ModbusClient 
   from pymodbus3.transaction import ModbusRtuFramer
   from serial.tools.list_ports import comports
   
   client = ModbusClient(method = "rtu", port = 'COM4',stopbits = 1, bytesize = 8, parity = 'N', baudrate= 19200)
   connection = client.connect()
   client.write_coil(1000, 1, unit = 0x01)
   

For reading coil status (function 0x01):

result = client.read_coils(1000,1)
print(result)
client.close()

Its returning None.

Or writing to register and reading is also not working:

client.write_register(0, 1000, unit=0x01)
resu= client.read_holding_registers(0, 1, unit=0x01)
print(resu)
client.close()

Positive response is welcomed!

This is a rather old question, but I want to put this information out there so there is less confusion.

pymodbus3 was a fork of pymodbus created to support python3 before pymodbus did so. pymodbus now fully supports python3 and pymodbus3 is no longer maintained and does not have all the latest that the original does.

See https://github.com/uzumaxy/pymodbus3/issues/7 for details.