import re
arr = ["mix butter , flour , 1 / 3 c", "sugar and 1-1 / 4 t", "vanilla"]
rx = re.compile(r'(?<!/)[ \t](?![ \t]*/)')
for i in arr:
print (rx.sub('', i))
aW1wb3J0IHJlCgphcnIgPSBbIm1peCBidXR0ZXIgLCBmbG91ciAsIDEgLyAzIGMiLCAic3VnYXIgYW5kIDEtMSAvIDQgdCIsICJ2YW5pbGxhIl0KCnJ4ID0gcmUuY29tcGlsZShyJyg/PCEvKVsgXHRdKD8hWyBcdF0qLyknKQoKZm9yIGkgaW4gYXJyOgoJcHJpbnQgKHJ4LnN1YignJywgaSkpCgk=