Converting float to bytes

[AidanRTaylor]

Hello - I'm trying to convert an ambient sensor readout into bytes so I can squeeze it down the LoRa tube! I can't seem to get the float.hex() attribute to work, I get this back: AttributeError: type object 'float' has no attribute 'hex'.

The Python3 docs say that float.hex() is a built in type, am I missing something here?

I tried the following:

temp = float.hex(sensordata)
temp = sensordata.hex()

Both return the same attribute error. Where am I going wrong? Is there a module I need to include? Here is the main module from my project:

import bme680
from bme680.i2c import I2CAdapter
from machine import Pin
import time
import struct

# Config pin:
configPin = Pin('P21', Pin.IN, Pin.PULL_UP)

# Setup I2C and BME680: P9/G16=SDA, P10/G17=SCL
i2c_dev = I2CAdapter(1, pins=('P9','P10'), baudrate=100000)
sensor = bme680.BME680(i2c_device=i2c_dev)

# These oversampling settings can be tweaked to
# change the balance between accuracy and noise in
# the data.
sensor.set_humidity_oversample(bme680.OS_2X)
sensor.set_pressure_oversample(bme680.OS_4X)
sensor.set_temperature_oversample(bme680.OS_8X)
sensor.set_filter(bme680.FILTER_SIZE_3)

config = configPin()

if config:
    while True:
        if sensor.get_sensor_data():

            output = "{} C, {} hPa, {} RH, {} RES,".format(
                sensor.data.temperature,
                sensor.data.pressure,
                sensor.data.humidity,
                sensor.data.gas_resistance)

            print(output)

            temp = float.hex(sensor.data.temperature)

            print(temp)

            time.sleep(5)

[robert-hh]

@aidanrtaylor use struct.pack() instead.

[AidanRTaylor]

thanks, trying it out now (I already had stuct imported as you can see above :P)

[timh]

@robert-hh beat me to it ;-)

struct.unpack('f',binascii.unhexlify(binascii.hexlify(struct.pack('f',1.234))))

and using 'e' instead of 'f' for the format will mean the float uses 4 bytes in hex form. at the loss of precision but doubt you need that much for temp ;-)

[AidanRTaylor]

isn't unpack the opposite of what I want? I thought I would need pack

Oh, I see you are showing me how to do both ;)

[robert-hh]

@aidanrtaylor Yes, you need pack() to make a bytes string out of a float, and unpack() will convert that back.
unpack() returns a tuple, wheras pack() in addition to a tuple accepts a single value.