import re


translation = {
    r'\{fuck\}': '{1}',
    'you': '{2}'
}

text ='{fuck} you'
pattern = re.compile(r'\b(' + '|'.join(translation.keys()) + r')\b')
print(r'\b(' + '|'.join(translation.keys()) + r')\b')
print(pattern.sub(lambda x: translation[x.group()], text))