import re
def replace(e):
return e
s = 'hi how are you today 23:i ok im good 1:e'
rx = r'(?<!\S)(\d{1,2}:[ie])(?!\S)|\S+'
print(re.sub(rx, lambda x: x.group(1) if x.group(1) else replace(x.group().lower()), s))
aW1wb3J0IHJlCgpkZWYgcmVwbGFjZShlKTogCglyZXR1cm4gZQoKcyA9ICdoaSBob3cgYXJlIHlvdSB0b2RheSAyMzppIG9rIGltIGdvb2QgMTplJwpyeCA9IHInKD88IVxTKShcZHsxLDJ9OltpZV0pKD8hXFMpfFxTKycKcHJpbnQocmUuc3ViKHJ4LCBsYW1iZGEgeDogeC5ncm91cCgxKSBpZiB4Lmdyb3VwKDEpIGVsc2UgcmVwbGFjZSh4Lmdyb3VwKCkubG93ZXIoKSksIHMpKQ==