find-package
name ⇒ package
If name is a string designator, find-package locates and returns the package whose name or nickname is name. This search is case sensitive. If there is no such package, find-package returns nil.
If name is a package object, that package object is returned.
(find-package 'common-lisp) ⇒ #<PACKAGE "COMMON-LISP">
(find-package "COMMON-LISP-USER") ⇒ #<PACKAGE "COMMON-LISP-USER">
(find-package 'not-there) ⇒ NIL
The set of packages created by the implementation.