feat(10): add an exercise, "Vector 3D" (#10)

Author: sohnryang

10-class-oop/guide.md

@@ -1 +1,10 @@
-# class and object-oriented-programming
+# class and object-oriented-programming
+
+## Vector 3D
+
+- difficulty: ★★★
+- time: ~ 45m for beginners
+- background: class, operator overloading
+
+Implement a class representing 3-dimensional vector.
+

10-class-oop/vector_3d-answer.py

@@ -0,0 +1,79 @@
+"""
+Implement a `Vector3D` class, which represents a 3D vector.
+
+You have to implement these for this class:
+- `__init__` magic function, which receives `x`, `y`, `z` and sets `self.x`,
+  `self.y`, `self.z` accordingly.
+
+>>> v = Vector3D(1, 2, 3)
+>>> v.x
+1
+>>> v.y
+2
+>>> v.z
+3
+
+- `to_tuple()` method, which converts the vector to a tuple in `(x, y, z)`
+  format.
+
+>>> v.to_tuple()
+(1, 2, 3)
+
+- `norm()` method, which calculates the norm (length) of the vector. The norm
+  can be calculated using sqrt(x^2 + y^2 + z^2).
+
+>>> v.norm() ** 2
+14.0
+
+- Addition between instances of `Vector3D`. The addition follows usual
+  component-wise addition rule.
+
+>>> w = Vector3D(4, 5, 6)
+>>> u = v + w
+>>> u.to_tuple()
+(5, 7, 9)
+
+- Substraction between instances of `Vector3D`. The Substraction also follows
+  usual component-wise substraction rule.
+
+>>> s = v - w
+>>> s.to_tuple()
+(-3, -3, -3)
+
+- Scalar multiplication of vector. `s * v`, where `s` is a number and `v` is an
+  instance of `Vector3D` gives an instance of `Vector3D` where its `x`, `y`, `z`
+  components are multiplied by `s`.
+
+>>> t = 3 * v
+>>> t.to_tuple()
+(3, 6, 9)
+"""
+import math
+
+
+class Vector3D:
+    def __init__(self, x, y, z):
+        self.x = x
+        self.y = y
+        self.z = z
+
+    def norm(self):
+        return math.sqrt(self.x**2 + self.y**2 + self.z**2)
+
+    def to_tuple(self):
+        return (self.x, self.y, self.z)
+
+    def __add__(self, rhs):
+        return Vector3D(self.x + rhs.x, self.y + rhs.y, self.z + rhs.z)
+
+    def __sub__(self, rhs):
+        return Vector3D(self.x - rhs.x, self.y - rhs.y, self.z - rhs.z)
+
+    def __rmul__(self, scalar):
+        return Vector3D(scalar * self.x, scalar * self.y, scalar * self.z)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod(verbose=True)

10-class-oop/vector_3d.py

@@ -0,0 +1,61 @@
+"""
+Implement a `Vector3D` class, which represents a 3D vector.
+
+You have to implement these for this class:
+- `__init__` magic function, which receives `x`, `y`, `z` and sets `self.x`,
+  `self.y`, `self.z` accordingly.
+
+>>> v = Vector3D(1, 2, 3)
+>>> v.x
+1
+>>> v.y
+2
+>>> v.z
+3
+
+- `to_tuple()` method, which converts the vector to a tuple in `(x, y, z)`
+  format.
+
+>>> v.to_tuple()
+(1, 2, 3)
+
+- `norm()` method, which calculates the norm (length) of the vector. The norm
+  can be calculated using sqrt(x^2 + y^2 + z^2).
+
+>>> v.norm() ** 2
+14.0
+
+- Addition between instances of `Vector3D`. The addition follows usual
+  component-wise addition rule.
+
+>>> w = Vector3D(4, 5, 6)
+>>> u = v + w
+>>> u.to_tuple()
+(5, 7, 9)
+
+- Substraction between instances of `Vector3D`. The Substraction also follows
+  usual component-wise substraction rule.
+
+>>> s = v - w
+>>> s.to_tuple()
+(-3, -3, -3)
+
+- Scalar multiplication of vector. `s * v`, where `s` is a number and `v` is an
+  instance of `Vector3D` gives an instance of `Vector3D` where its `x`, `y`, `z`
+  components are multiplied by `s`.
+
+>>> t = 3 * v
+>>> t.to_tuple()
+(3, 6, 9)
+"""
+import math
+
+
+class Vector3D:
+    pass
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod(verbose=True)