Add pip installer.

lib/sprinkle/installers/pip.rb

@@ -0,0 +1,51 @@
+module Sprinkle
+  module Installers
+    # The pip package installer installs Python packages.
+    #
+    #
+    # == Example Usage
+    #
+    # A simple installation:
+    #
+    #   package :magic_beans do
+    #     description "Beans beans they're good for your heart..."
+    #     pip 'magic_beans'
+    #   end
+    #
+    # You may also specify multiple packages as an array:
+    #
+    #   package :magic_beans do
+    #     pip %w(magic_beans magic_sauce)
+    #   end
+    #
+    class Pip < Installer
+
+      ##
+      # installs the pip packages passed
+      # :method: pip
+      # :call-seq: pip(*packages)
+      auto_api
+
+      verify_api do
+        def has_pip(package)
+          # `pip show INSTLLED` outputs something like:
+          #
+          #      ---
+          #      Name: bean
+          #      ...
+          #
+          # And `pip show UNINSTALLED` outputs nothing (exit code is still 0).
+          # Thus we only need to match `-` once.
+          @commands << "pip show #{package} | grep -F -m 1 '-'"
+        end
+      end
+
+      protected
+
+        def install_commands #:nodoc:
+          cmd = "#{sudo_cmd}pip install #{@packages.join(' ')}"
+        end
+
+    end
+  end
+end