MiniPowerReaderModbus.py

#!/usr/bin/env python3
import minimalmodbus
import serial

powerMeter = minimalmodbus.Instrument('/dev/ttyUSB0', 1) 
powerMeter.serial.baudrate = 9600
powerMeter.serial.bytesize = 8
powerMeter.serial.parity   = serial.PARITY_NONE
powerMeter.serial.stopbits = 1
powerMeter.mode = minimalmodbus.MODE_RTU

# Print the details of the power meter here, these also include the config needed to talk to the unit.
print('Details of the power meter are:')
print(powerMeter)


def readPowerMeter():
    print("Attempting to read power meter")
    try:
        voltageReading = powerMeter.read_register(0, 0, 4)
        ampsReading = powerMeter.read_register(1, 0, 4)
        wattsReading = powerMeter.read_register(3, 0, 4)
        frequencyReading = powerMeter.read_register(7, 0, 4)
        print("Voltage", voltageReading/10)
        print("Amps", ampsReading/10)
        print("Watts", wattsReading/10)
        print("Frequency", frequencyReading/10)        
    except IOError:
        print("Failed to read from instrument")

# Run the function to read the power meter.
readPowerMeter()

Thanks for this reference code.
The hardware documentation for the PZEM-016 indicates that the current, power, and cumulative energy measurements are contained in two adjacent registers. I could not get the multi-register read to work on the PZEM-016 so used two 16-bit reads instead and shifted the high-16 bits up before adding in the low 16-bits.

e.g.
watts = ((powerMeter.read_register(4, 0, 4) << 16) + powerMeter.read_register(3, 0, 4))/10.