Untitled

Context dependent split of a string in python
s = '2-Methyl-3-phythyl-1,4-naphthochinon,Vitamin, K1,Antihemorrhagic vitamin'

splitS = ['2-Methyl-3-phythyl-1,4-naphthochinon', 'Vitamin, K1', 'Antihemorrhagic vitamin']

>>> s = '2-Methyl-3-phythyl-1,4-naphthochinon,Vitamin, K1,Antihemorrhagic vitamin'
>>> pat = re.compile("([^ds],[^ds])|([^s],[^ds])|([^ds],[^s])")
>>> re.split(pat, s)
['2-Methyl-3-phythyl-1,4-naphthochino', 'n,V', None, None, 'itamin, K', None, '1,A', None, 'ntihemorrhagic vitamin']

(?<!d),(?! )|(?<=d),(?![d ])

>>> re.split(r'(?<!d),(?! )|(?<=d),(?![d ])', s)
['2-Methyl-3-phythyl-1,4-naphthochinon', 'Vitamin, K1', 'Antihemorrhagic vitamin']

(?<!d),   # match a comma that is not preceeded by a digit...
 (?! )      # ... as long as it is not followed by a space
|           # OR
 (?<=d),   # match a comma that is preceeded by a digit...
 (?![d ])  # ... as long as it is not followed by a digit or a space

(?<!d),(?! )|,(?![d ])

s = '2-Methyl-3-phythyl-1,4-naphthochinon,Vitamin, K1,Antihemorrhagic vitamin'

all_commas = [match.start() for match in re.finditer(r',', s)]
special_commas = [match.start()+1 for match in re.finditer(r'd,d|.,s', s)]

split_commas = set(all_commas) - set(special_commas)

splitS = []
start = -1
for end in sorted(split_commas) + [None]:
    splitS.append(s[start+1:end])
    start = end

>>> splitS
['2-Methyl-3-phythyl-1,4-naphthochinon', 'Vitamin, K1', 'Antihemorrhagic vitamin']