import re
new_ = {
   '&&':'and',
   '||':'or'
}
inpStr = "good && toast&&guest &fast& slow||wind ||old|| new || very good"
replDictRe = re.compile( r'(?<!\S)(?:{})(?!\S)'.format('|'.join(map(re.escape, new_.keys()))) )
print(replDictRe.pattern)
oidDesStr = replDictRe.sub(lambda mo:new_.get(mo.group(),mo.group()), inpStr)
print(oidDesStr)