Pickle

Q: How deeply does Fast Python: High performance techniques for large datasets cover pickle?

Shows serialization and reconstruction, then details multiprocessing limits including lambda failures and transfer overhead.

As explained in Fast Python: High performance techniques for large datasets

Pickle is Python’s standard-library facility for serializing Python objects to byte streams and reconstructing them from those streams.

Pickle serializes Python data into bytes and reconstructs data from those bytes. It commonly carries objects between processes, but it does not transfer code. section 3.1.3

Account for these practical limits when choosing pickle for communication:

Lambdas cannot be pickled with the default configuration, so a process pool cannot transfer them as-is; rewriting a lambda as a named function fixes the demonstrated case. section 3.4.1
Foreign-library objects may need separate handling; file pointers, database connections, and sockets may be impossible to transfer or require extra care. section 3.4.1
Serialization and interprocess communication can be slow enough to undermine multiprocessing when data volumes are large. section 3.4.1

Sending data over a socket

A synchronous client pickles its data, sends the byte length and payload over TCP, and uses a separate mechanism to transfer code. The example highlights that framing and compact, fast encoding may require handling outside pickle. section 3.1.3

<Future at 0x7f1ffff104c0 state=finished raised PicklingError>
Can't pickle <function <lambda> at 0x7f2000131ca0>: attribute lookup
  <lambda> on __main__ failed

The failed future shows the pickling error raised when the process pool tries to transfer a lambda. section 3.4.1

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Also explained in

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Python How-ToPickling is Python's serialization process for converting objects into a byte stream that can be stored and later reconstructed.
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The Quick Python Book, Fourth Editionpickle is a Python standard-library serialization facility for converting Python objects to and from a byte stream.

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Related concepts

byte streamproduces · A byte stream is an ordered flow of bytes representing binary data for storage, processing, transmission, or incremental reading without inherent message semantics.
multiprocessingused by · Multiprocessing is a programming technique that executes work in multiple operating-system processes, enabling concurrent or parallel execution across available processor resources.
JSONcontrasts with · JSON is a standardized, language-independent text format for representing structured data using objects, arrays, strings, numbers, Boolean values, and null.
lambdacontrasts with · A lambda is a language construct that defines an unnamed function or callable, often as a value.
cachingused by · Caching is the practice of storing reusable data or computation results so later access can avoid repeating retrieval or computation.

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