quatpy 2025.1.1

A set of functions to manipulate quaternions.

Python Quaternions (quatpy)

A lightweight Python package for handling quaternions. This package provides efficient tools for working with quaternions, including conversions between different rotation representations (Euler angles, rotation matrices) and common quaternion operations.

Quick Examples

1. Basic Quaternion Operations

pip install https://github.com/jchar32/quaternions.git

or

pip install quatpy

Verify installation:

import quaternions
print(quaternions.__version__)

import numpy as np
from quaternions import normalize, product

# Create two quaternions (scalar-first format)
q1 = np.array([1, 0, 1, 0])  # [w, x, y, z]
q2 = np.array([0, 1, 0, 1])

# Normalize and multiply quaternions
q1_norm = normalize(q1)
q2_norm = normalize(q2)
result = product(q1_norm, q2_norm)

2. Rotating Vectors

from quaternions import from_angles, quat_rotate

# Create rotation quaternion from Euler angles (in radians)
angles = np.array([np.pi/4, 0, 0])  # 45° rotation around x-axis
q = from_angles(angles)

# Rotate a vector
vector = np.array([0, 0, 1])
rotated_vector = quat_rotate(q, vector)

3. Converting Between Representations

from quaternions import from_rotmat, to_angles

# Create rotation matrix
R = np.array([[0, -1, 0],
              [1,  0, 0],
              [0,  0, 1]])

# Convert to quaternion and then to Euler angles
q = from_rotmat(R)
euler_angles = to_angles(q, order='xyz')
print(f"Euler angles (degrees): {np.degrees(euler_angles)}")