Accidentally deleted iPhoto and lost all of my photos, how can I get the photos back?

Not sure how I did it, but iPhoto is gone from my computer, along with all of my 800+ photos. How can I get my photos back? I reinstalled iPhoto and signed in, but it is empty.

Assuming you didn’t delete your iPhoto Library, but just iPhoto

1. Reinstall iPhoto from the Mac App Store [you did this, go to 2]
2. Hold down the option key while opening iPhoto to select a different default library. The current default is the empty library. We want to track down your original library.
3. Click “Choose library...”
4. By default, your iPhoto Library is located in /Volumes/<HDNAME>/Users/<USERNAME>/Pictures/. Assuming you haven’t deleted the library itself, or moved it to a different location, your original iPhoto Library will be located in your pictures folder. It will be labeled iPhoto Library_2.iphotolibrary, iPhoto Library.iphotolibrary~old or something of that nature. I don’t know what the exact name will be. You will be able to tell the new from the old simply by examining the size (800 photos will be atleast a couple GB’s). Select the old library.
5. When iPhoto opens, your original library should be present and intact. If it’s not, you’ve just selected the current default library. Repeat steps 2-4 in this case.
6. Once you have identified the correct original library - using step 5 - you can now safely delete the empty (false) iPhoto Library from your pictures folder. Your original iPhoto library is now your default.