What was Harry Potter's reaction when he learned that Severus Snape was good?

Answer 1

As Harry watches Snape bleed to death on the floor of the Shrieking Shack, Snape starts oozing memories, in the form of a silvery-blue substance, out of his ears and nose and eyes, and Harry gathers them up in a vial that Hermione conjures for him.

He goes to Dumbledore's office, puts the memories into the Pensieve, and watches them. The memories chronicle some of the most important scenes and events of Snape's life, from his childhood with Lily Evans, to the events surrounding Lily and James' death, up until just a few months before his own death. In a nutshell, the memories prove to Harry that Snape was Dumbledore's man, through and through.

Answer 2

Harry didn't really find out that Snape was good - he just found out that he was wrong and that Professor Quirrell was the one working with Lord Voldemort and trying to steal the Philosopher's Stone.

Answer 3

Chapter 33 "The Prince's Tale" of Harry Potter and the Deathly Hallows

Harry looks at Snape's memories in the pensieve and learns that Snape was a double agent working for Dumbledore and that he loved Lily Potter which is why his patronus is a doe because Lily's was a doe too.

Answer 4

Harry didn't really have time to react, he was a little more concerned with the fact that he had to go die at the hands of Voldemort. He later names one of his children Albus Severus after the two bravest men he ever knew.

Answer 5

There are some hints, especially throughout book six, but they are not so obvious. Only at the end of book seven is it clearly revealed what actually happened.