#!/usr/bin/env python3
from curses import echo
import glob
import time
import sys

base_dir = '/sys/bus/w1/devices/'
# Get all the filenames begin with 28 in the path base_dir.
devices = glob.glob(base_dir + '28*')
if not devices:
    print("No DS18B20 temperature sensor detected")
    sys.exit(0)
device_folder = devices[0]
device_file = device_folder + '/w1_slave'


def read_rom():
    name_file = device_folder+'/name'
    f = open(name_file, 'r')
    return f.readline()


def read_temp_raw():
    f = open(device_file, 'r')
    lines = f.readlines()
    f.close()
    return lines


def read_temp():
    lines = read_temp_raw()
    # Analyze if the last 3 characters are 'YES'.
    while lines[0].strip()[-3:] != 'YES':
        time.sleep(0.2)
        lines = read_temp_raw()
    # Find the index of 't=' in a string.
    equals_pos = lines[1].find('t=')
    if equals_pos != -1:
        # Read the temperature .
        temp_string = lines[1][equals_pos+2:]
        temp_c = float(temp_string) / 1000.0
        return temp_c


if __name__ == '__main__':
    print("{:.3f}".format(read_temp()))
