After update to 10.10.4 iphoto doesn't work

Try this, it should be relevant for OSX10.10.4 also

See here: Get iPhoto 9.6.1 if you didn't update before OS X 10.10.3

Pete

Go to the App Store and check out the Purchases List. If iPhoto is there then it will be v9.6.1

If it is there, then drag your existing iPhoto app (not the library, just the app) to the trash.

Install the App from the App Store.

Sometimes iPhoto is not visible on the Purchases List. it may be hidden. See this article for details on how to unhide it.

http://support.apple.com/kb/HT4928

One question often asked: Will I lose my Photos if I reinstall?

iPhoto the application and the iPhoto Library are two different parts of the iPhoto programme. So, reinstalling the app should not affect the Library. BUT you should always have a back up before doing this kind of work. Always.