add sperical_from_cartesian

qctools/tools.py

@@ -0,0 +1,30 @@
+import numpy as np
+
+def spherical_from_cartesian(x, y, z):
+    """
+    Convert cartesian coordinates to spherical coordinates.
+    
+    Parameters
+    ----------
+    x : float
+        x-coordinate
+    y : float
+        y-coordinate
+    z : float
+        z-coordinate
+        
+    Returns
+    -------
+    r : float
+        radial coordinate
+    theta : float
+        polar angle
+    phi : float
+        azimuthal angle
+    """
+
+    r = np.sqrt(x**2 + y**2 + z**2 )
+    theta = np.arccos(z/r)
+    phi = np.arctan2(y, x)
+
+    return np.array([r, theta, phi])

tests/test_tools.py

@@ -0,0 +1,26 @@
+from qctools.tools import *
+import numpy as np
+
+def test_spherical_from_cartesian():
+    """
+    testing spherical_from_cartesian function
+    """
+    np.random.seed(42)
+    x_lst = np.random.uniform(-1, 1, 10)
+    y_lst = np.random.uniform(-1, 1, 10)
+    z_lst = np.random.uniform(-1, 1, 10)
+
+    res = []
+    for x, y, z in zip(x_lst, y_lst, z_lst):
+        res.append(spherical_from_cartesian(x, y, z))
+
+    res = np.array(res) 
+
+    # convert back to cartesian
+    x_res = res[:, 0] * np.sin(res[:, 1]) * np.cos(res[:, 2])
+    y_res = res[:, 0] * np.sin(res[:, 1]) * np.sin(res[:, 2])
+    z_res = res[:, 0] * np.cos(res[:, 1])
+
+    np.testing.assert_allclose(x_res, x_lst, atol=1e-5, rtol=1e-5)
+    np.testing.assert_allclose(y_res, y_lst, atol=1e-5, rtol=1e-5)
+    np.testing.assert_allclose(z_res, z_lst, atol=1e-5, rtol=1e-5)