pop(0) from empty list (including proposal for a fix)

[markfink]

hi Harry,

thanks for sharing this. It turns out to be very helpful. Unfortunately sometimes I get into trouble when your code pop from an empty list (see below).

This is my proposal for a fix but there might be a more clever alternative...
def next (prevList):
sum = 0.0
retval = ""
index = random.random ()
# Shorten prevList until it's in mapping
while toHash (prevList) not in mapping:
if prevList:
prevList.pop (0) # cant pop from empty list
else:
curr = random.choice (starts)
sent = curr.capitalize ()
prevList = [curr]
# Get a random word from the mapping, given prevList
for k, v in mapping [toHash (prevList)].iteritems ():
sum += v
if sum >= index and retval == "":
retval = k
return retval

all the best,
Mark

Traceback (most recent call last):
File "dbutils.py", line 92, in
insert_news(2000)
File "dbutils.py", line 84, in insert_news
title, content, upd_at = create_one(gen)
File "dbutils.py", line 73, in create_one
content = content + gen() + ' '
File "/home/mark/devel/boodo/boodo/boodo/utils/markovgen/generator.py", line 14, in gen
return genSentence(1)
File "/home/mark/devel/boodo/boodo/boodo/utils/markovgen/sentence.py", line 117, in genSentence
curr = next (prevList)
File "/home/mark/devel/boodo/boodo/boodo/utils/markovgen/sentence.py", line 102, in next
prevList.pop (0)
IndexError: pop from empty list

[elacsoft]

please write clear indents in else field.