.. _Introduction: Introduction ============== Traditional machine learning systems are deployed under the closed-world setting, which requires the entire training data before the offline training process. However, real-world applications often face the incoming new classes, and a model should incorporate them continually. The learning paradigm is called Class-Incremental Learning (CIL). We propose a Python toolbox that implements several key algorithms for class-incremental learning to ease the burden of researchers in the machine learning community. The toolbox contains implementations of a number of founding works of CIL, such as EWC and iCaRL, but also provides current state-of-the-art algorithms that can be used for conducting novel fundamental research. This toolbox, named PyCIL for Python Class-Incremental Learning, is open source with an MIT license. For more information about incremental learning, you can refer to these reading materials: * A brief introduction (in Chinese) about CIL is available `here `_. * A PyTorch Tutorial to Class-Incremental Learning (with explicit codes and detailed explanations) is available `here `_.