import re
p = r'\w+@\w+[.]\w+[\w.]+|\w+\(at\)\w+[.]\w+[\w.]+|\w+\sat\s[\w-]+\sdot\s\w+\sdot\s\w+'
t = 'developed and application for harvest any type of emails from files types : ishani@dolly.lk ishani(at)dit.dolly.lk ishani at cs dot dolly dot edu'
print(re.findall(p, t))
aW1wb3J0IHJlCgpwID0gcidcdytAXHcrWy5dXHcrW1x3Ll0rfFx3K1woYXRcKVx3K1suXVx3K1tcdy5dK3xcdytcc2F0XHNbXHctXStcc2RvdFxzXHcrXHNkb3Rcc1x3KycKdCA9ICdkZXZlbG9wZWQgYW5kIGFwcGxpY2F0aW9uIGZvciBoYXJ2ZXN0IGFueSB0eXBlIG9mIGVtYWlscyBmcm9tIGZpbGVzIHR5cGVzIDogaXNoYW5pQGRvbGx5LmxrIGlzaGFuaShhdClkaXQuZG9sbHkubGsgaXNoYW5pIGF0IGNzIGRvdCBkb2xseSBkb3QgZWR1JwpwcmludChyZS5maW5kYWxsKHAsIHQpKQ==