import re
l=[u'i like cats and dogs',u'i like catnip plant', u'i like cars']
for s in l:
#match cat until whitespace
m = re.search(r"cat\S*",s)
if m:
print(m.group())
aW1wb3J0IHJlCmw9W3UnaSBsaWtlIGNhdHMgYW5kIGRvZ3MnLHUnaSBsaWtlIGNhdG5pcCBwbGFudCcsIHUnaSBsaWtlIGNhcnMnXQpmb3IgcyBpbiBsOgoJI21hdGNoIGNhdCB1bnRpbCB3aGl0ZXNwYWNlCgltID0gcmUuc2VhcmNoKHIiY2F0XFMqIixzKQoJaWYgbToKCQlwcmludChtLmdyb3VwKCkp