diff --git a/.rubocop.yml b/.rubocop.yml
index 720d21a..b496855 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -100,6 +100,13 @@ Style/MultilineBlockChain:
 Metrics/ParameterLists:
   Max: 10
 
+### Naming
+
+Naming/UncommunicativeMethodParamName:
+  AllowedNames:
+    - db
+    - str
+
 ### RSpec --------------------------------------------------------------
 
 RSpec/MessageSpies:
diff --git a/daru-io.gemspec b/daru-io.gemspec
index cd79014..21e127f 100644
--- a/daru-io.gemspec
+++ b/daru-io.gemspec
@@ -1,4 +1,5 @@
-lib = File.expand_path('../lib', __FILE__)
+
+lib = File.expand_path('lib', __dir__)
 $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'daru/io/version'
 
diff --git a/lib/daru/io/exporters/excel.rb b/lib/daru/io/exporters/excel.rb
index bc7662e..b769656 100755
--- a/lib/daru/io/exporters/excel.rb
+++ b/lib/daru/io/exporters/excel.rb
@@ -98,8 +98,10 @@ def write(path)
 
         def process_offsets
           @row_offset   = @header ? 1 : 0
+          # rubocop:disable Naming/MemoizedInstanceVariableName
           @col_offset   = 0 unless @index
           @col_offset ||= @dataframe.index.is_a?(Daru::MultiIndex) ? @dataframe.index.width : 1
+          # rubocop:enable Naming/MemoizedInstanceVariableName
         end
 
         def write_headers
diff --git a/lib/daru/io/importers/html.rb b/lib/daru/io/importers/html.rb
index 065da21..e4b2876 100644
--- a/lib/daru/io/importers/html.rb
+++ b/lib/daru/io/importers/html.rb
@@ -30,7 +30,7 @@ def initialize
         # @example Reading from a website url file
         #   instance = Daru::IO::Importers::HTML.read('http://www.moneycontrol.com/')
         def read(path)
-          @file_data = Nokogiri.parse(open(path).read)
+          @file_data = Nokogiri.parse(File.open(path).read)
           self
         end
 
diff --git a/lib/daru/io/importers/plaintext.rb b/lib/daru/io/importers/plaintext.rb
index af0bda4..a6bd975 100644
--- a/lib/daru/io/importers/plaintext.rb
+++ b/lib/daru/io/importers/plaintext.rb
@@ -81,14 +81,14 @@ def process_row(row,empty)
           end
         end
 
-        def try_string_to_number(s)
-          case s
+        def try_string_to_number(str)
+          case str
           when INT_PATTERN
-            s.to_i
+            str.to_i
           when FLOAT_PATTERN
-            s.tr(',', '.').to_f
+            str.tr(',', '.').to_f
           else
-            s
+            str
           end
         end
       end
diff --git a/spec/daru/io/exporters/csv_spec.rb b/spec/daru/io/exporters/csv_spec.rb
index e3dad6b..2c58531 100644
--- a/spec/daru/io/exporters/csv_spec.rb
+++ b/spec/daru/io/exporters/csv_spec.rb
@@ -1,3 +1,4 @@
+
 RSpec.describe Daru::IO::Exporters::CSV do
   subject { File.open(tempfile.path, &:readline).chomp.split(',', -1) }
 
@@ -48,7 +49,7 @@
   end
 
   context 'writes into .csv.gz format' do
-    subject        { Zlib::GzipReader.new(open(tempfile.path)).read.split("\n") }
+    subject        { Zlib::GzipReader.new(File.open(tempfile.path)).read.split("\n") }
 
     let(:opts)     { {compression: :gzip} }
     let(:filename) { 'test.csv.gz'        }