Python Value error - python-2.7

Question

I'm getting an error when trying to split a piped output into python.
Error is need more than 3 values to unpack although I'm using 8 values
import subprocess, sys
from datetime import datetime
from time import sleep as sleep
multimon_ng = subprocess.Popen("multimon-ng -a FLEX -t wav flex.wav",
stdout=subprocess.PIPE,
stderr=subprocess.PIPE,
shell=True)
while True:
nextline = multimon_ng.stdout.readline()
flex, mdate, mtime, bitrate, other, capcode, o2, msg = nextline.split(" ", 7) # error here
if nextline is " ":
print "napping"
else:
print mdate + " " + mtime + " " + capcode + " " + msg
multimon_ng.poll()
sys.stdout.flush()
any help would be great

Answer 1

3 in error message indicated length of iterable in right hand side argument.
Minimal wrong examples:
a, = [] # ValueError: need more than 0 values to unpack
a, b = [1] # ValueError: need more than 1 value to unpack
a, b, c = [1, 2] # ValueError: need more than 2 values to unpack
# etc ...
Minimal correct examples:
a, = [1]
a, b = [1, 2]
a, b, c = [1, 2, 3]
Smallest change to fix and expose issue would be to wrap unpacking iterable in try-except block.
while True:
nextline = multimon_ng.stdout.readline()
if not nextline:
print "napping"
else:
try:
flex, mdate, mtime, bitrate, other, capcode, o2, msg = nextline.split(" ", 7)
except ValueError:
print "invalid line", nextline
else:
print mdate + " " + mtime + " " + capcode + " " + msg
multimon_ng.poll()
sys.stdout.flush()
As you can see, I also moved check for empty line before unpacking. If line is empty, unpacking would also fail.