What is Pickle?

Pickle is a Python module that implements binary protocols for serializing and de-serializing Python object structures. 'Pickling' is the process where a Python object hierarchy is converted into a byte stream, and 'unpickling' is the inverse operation, whereby a byte stream is converted back into an object hierarchy. It is commonly used for saving and loading machine learning models, caching data, and transmitting Python objects over a network. However, it is important to be very careful when unpickling data from untrusted sources, because arbitrary code execution is possible.