diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 0000000..0b9a44b
Binary files /dev/null and b/.DS_Store differ
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..7b1425a
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,37 @@
+name: CI Pipeline
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.10", "3.11"]
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v3
+
+    - name: Set up Python
+      uses: actions/setup-python@v4
+      with:
+        python-version: ${{ matrix.python-version }}
+
+    - name: Install dependencies
+      run: |
+        pip install pytest flake8 coverage
+
+    - name: Lint code
+      run: flake8 .
+
+    - name: Run tests
+      run: pytest
+
+    - name: Run coverage
+      run: |
+        coverage run -m pytest
+        coverage report
\ No newline at end of file
diff --git a/calculator/__init__.py b/calculator/__init__.py
index 871f6fd..3891761 100644
--- a/calculator/__init__.py
+++ b/calculator/__init__.py
@@ -1 +1 @@
-from .calculator import Calculator
+from .calculator import Calculator  # noqa: F401
diff --git a/calculator/calculator.py b/calculator/calculator.py
index 934990d..d907f13 100644
--- a/calculator/calculator.py
+++ b/calculator/calculator.py
@@ -3,7 +3,8 @@
 
 class Calculator:
 
-    """Calculator class with methods to sum, subtract, multiply, divide square and find square root"""
+    """Calculator class with methods to sum, subtract, multiply,
+divide, square, and find square root."""
 
     def __init__(self, memory=0):
         self.memory = memory
@@ -28,12 +29,12 @@ def sum(self, a, b=None):
         """
 
         try:
-            if b == None:
+            if b is None:
                 b = self.memory
 
             self.memory = float(a) + float(b)
             return self.memory
-        except:
+        except Exception:
             return 'Invalid input'
 
     def subtract(self, a, b=None):
@@ -49,13 +50,13 @@ def subtract(self, a, b=None):
         """
 
         try:
-            if b == None:
+            if b is None:
                 b = a
                 a = self.memory
 
             self.memory = float(a) - float(b)
             return self.memory
-        except:
+        except Exception:
             return 'Invalid input'
 
     def multiply(self, a, b=None):
@@ -71,12 +72,12 @@ def multiply(self, a, b=None):
         """
 
         try:
-            if b == None:
+            if b is None:
                 b = self.memory
 
             self.memory = float(a) * float(b)
             return self.memory
-        except:
+        except Exception:
             return 'Invalid input'
 
     def divide(self, a, b=None):
@@ -92,7 +93,7 @@ def divide(self, a, b=None):
         """
 
         try:
-            if b == None:
+            if b is None:
                 b = a
                 a = self.memory
 
@@ -100,7 +101,7 @@ def divide(self, a, b=None):
             return self.memory
         except ZeroDivisionError:
             return 'Can not divide by zero.'
-        except:
+        except Exception:
             return 'Invalid input'
 
     def square(self, a=None):
@@ -115,12 +116,12 @@ def square(self, a=None):
         """
 
         try:
-            if a == None:
+            if a is None:
                 a = self.memory
 
             self.memory = float(a) ** 2
             return self.memory
-        except:
+        except Exception:
             return 'Invalid input'
 
     def sqrt(self, a=None):
@@ -135,10 +136,10 @@ def sqrt(self, a=None):
         """
 
         try:
-            if a == None:
+            if a is None:
                 a = self.memory
 
             self.memory = math.sqrt(float(a))
             return self.memory
-        except:
+        except Exception:
             return 'Invalid input'
diff --git a/tests/test_calculator.py b/tests/test_calculator.py
index 1a2d7b6..84f283f 100644
--- a/tests/test_calculator.py
+++ b/tests/test_calculator.py
@@ -1,5 +1,3 @@
-import pytest
-
 from calculator.calculator import Calculator
 
 c = Calculator()