diff --git a/calculator/calculator/__init__.py b/calculator/calculator/__init__.py
new file mode 100644
index 0000000..ba34e1e
--- /dev/null
+++ b/calculator/calculator/__init__.py
@@ -0,0 +1 @@
+import calculator.ast
diff --git a/calculator/calculator/ast/__init__.py b/calculator/calculator/ast/__init__.py
new file mode 100644
index 0000000..aba748c
--- /dev/null
+++ b/calculator/calculator/ast/__init__.py
@@ -0,0 +1,4 @@
+from .node import Node  # isort:skip
+from .binop import BinOp
+from .constant import Constant
+from .unaryop import UnaryOp
diff --git a/calculator/calculator/ast/binop.py b/calculator/calculator/ast/binop.py
new file mode 100644
index 0000000..a091bbd
--- /dev/null
+++ b/calculator/calculator/ast/binop.py
@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Callable
+
+from pydantic.dataclasses import dataclass
+
+from .node import Node
+
+if TYPE_CHECKING:
+    from calculator.ast.visit import Visitor
+
+
+class Config:
+    arbitrary_types_allowed = True
+
+
+@dataclass(config=Config)
+class BinOp(Node):
+    """
+    Node to represent a binary operation
+    """
+
+    op: Callable[[int, int], int]
+    lhs: Node
+    rhs: Node
+
+    def accept(self, v: Visitor) -> None:
+        v.visit_binop(self)
diff --git a/calculator/calculator/ast/constant.py b/calculator/calculator/ast/constant.py
new file mode 100644
index 0000000..833f507
--- /dev/null
+++ b/calculator/calculator/ast/constant.py
@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from pydantic.dataclasses import dataclass
+
+from .node import Node
+
+if TYPE_CHECKING:
+    from calculator.ast.visit import Visitor
+
+
+class Config:
+    arbitrary_types_allowed = True
+
+
+@dataclass(config=Config)
+class Constant(Node):
+    """
+    Node to represent a constant value.
+    """
+
+    value: int
+
+    def accept(self, v: Visitor) -> None:
+        v.visit_constant(self)
diff --git a/calculator/calculator/ast/node.py b/calculator/calculator/ast/node.py
new file mode 100644
index 0000000..dfbdf85
--- /dev/null
+++ b/calculator/calculator/ast/node.py
@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from calculator.ast.visit import Visitor
+
+
+class Node(ABC):
+    """
+    Abstract Node class for calculator AST.
+    """
+
+    @abstractmethod
+    def accept(self, v: Visitor) -> None:
+        pass
diff --git a/calculator/calculator/ast/unaryop.py b/calculator/calculator/ast/unaryop.py
new file mode 100644
index 0000000..38f2877
--- /dev/null
+++ b/calculator/calculator/ast/unaryop.py
@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Callable
+
+from pydantic.dataclasses import dataclass
+
+from .node import Node
+
+if TYPE_CHECKING:
+    from calculator.ast.visit import Visitor
+
+
+class Config:
+    arbitrary_types_allowed = True
+
+
+@dataclass(config=Config)
+class UnaryOp(Node):
+    """
+    Node to represent a unary operation
+    """
+
+    op: Callable[[int], int]
+    rhs: Node
+
+    def accept(self, v: Visitor) -> None:
+        v.visit_unaryop(self)
diff --git a/calculator/calculator/ast/visit/__init__.py b/calculator/calculator/ast/visit/__init__.py
new file mode 100644
index 0000000..8bf79fe
--- /dev/null
+++ b/calculator/calculator/ast/visit/__init__.py
@@ -0,0 +1 @@
+from .visitor import Visitor  # isort:skip
diff --git a/calculator/calculator/ast/visit/visitor.py b/calculator/calculator/ast/visit/visitor.py
new file mode 100644
index 0000000..c111215
--- /dev/null
+++ b/calculator/calculator/ast/visit/visitor.py
@@ -0,0 +1,28 @@
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from calculator.ast import BinOp, Constant, Node, UnaryOp
+
+
+class Visitor(ABC):
+    """
+    Abstract Visitor class for the AST class hierarchy.
+    """
+
+    def visit(self, n: Node) -> None:
+        n.accept(self)
+
+    @abstractmethod
+    def visit_constant(self, c: Constant) -> None:
+        pass
+
+    @abstractmethod
+    def visit_binop(self, b: BinOp) -> None:
+        pass
+
+    @abstractmethod
+    def visit_unaryop(self, b: UnaryOp) -> None:
+        pass