import re
r = re.compile(r"Prompt:(?![ \t]*\n)")
# Doesn't match because no text between Prompt: and \n
s = 'Prompt: \n'
m = r.search(s)
if m:
print "m: " + m.group(0)
# Matches because text exists between Prompt: and \n
s2 = 'Prompt: Something\n'
m2 = r.search(s2)
if m2:
print "m2: " + m2.group(0)
aW1wb3J0IHJlCgpyID0gcmUuY29tcGlsZShyIlByb21wdDooPyFbIFx0XSpcbikiKQoKIyBEb2Vzbid0IG1hdGNoIGJlY2F1c2Ugbm8gdGV4dCBiZXR3ZWVuIFByb21wdDogYW5kIFxuCnMgPSAnUHJvbXB0OiBcbicKbSA9IHIuc2VhcmNoKHMpCmlmIG06CglwcmludCAibTogIiArIG0uZ3JvdXAoMCkKCiMgTWF0Y2hlcyBiZWNhdXNlIHRleHQgZXhpc3RzIGJldHdlZW4gUHJvbXB0OiBhbmQgXG4KczIgPSAnUHJvbXB0OiBTb21ldGhpbmdcbicKbTIgPSByLnNlYXJjaChzMikKaWYgbTI6CglwcmludCAibTI6ICIgKyBtMi5ncm91cCgwKQ==