Try with these changes:
#DWM Serial Parser by Brian H. | Updated 3/6/19
import serial
import time
import datetime
DWM=serial.Serial(port="/dev/serial0", baudrate=115200)
print("Connected to " +DWM.name)
DWM.write("\r\r".encode())
time.sleep(1)
DWM.write("lec\r".encode())
time.sleep(1)
while True:
try:
line=DWM.readline()
if(line):
parse=line.decode().split(",")
if parse[0]=="DIST":
pos_AN0=(parse[parse.index("AN0")+2],parse[parse.index("AN0")+3],parse[parse.index("AN0")+4])
dist_AN0=parse[parse.index("AN0")+5]
print(datetime.datetime.now().strftime("%H:%M:%S"),pos_AN0,":",dist_AN0)
else:
print("Distance not calculated: ",line.decode())
except Exception as ex:
print(ex)
break
DWM.write("\r".encode())
DWM.close()