Caterpillar is a Python 3.12 library to pack and unpack structurized binary data. It enhances the capabilities of Python Struct by enabling direct class declaration. More information about the different configuration options will be added in the future. Documentation is here >.

Caterpillar is able to:

• Pack and unpack data just from processing Python class definitions (including support for bitfields, c -like templates and c-like unions!),
• apply a wide range of data types (with endianess and architecture configuration),
• dynamically adapt structs based on their inheritance layout,
• reduce the used memory space using __slots__,
• allowing you to place conditional statements into class definitions,
• insert proper types into the class definition to support documentation and
• it helps you to create cleaner and more compact code.
• You can even extend Caterpillar and write your parsing logic in C or C !!

from caterpillar.py import *

@struct(order=LittleEndian)
class Format:
    magic: b"ITS MAGIC"       # Supports string and byte constants directly
    a: uint8                  # Primitive data types
    b: int32
    length: uint8             # String fields with computed lengths
    name: String(this.length) #  -> you can also use Prefixed(uint8)
    names: CString[uint8::]   # Sequences with prefixed, computed lengths

# Instantiation (keyword-only arguments, magic is auto-inferred):
obj = Format(a=1, b=2, length=3, name="foo", names=["a", "b"])
# Packing the object:
blob = pack(obj) # objects of struct classes can be packed right away
# results in: b'ITS MAGIC\x01\x02\x00\x00\x00\x03foo\x02a\x00b\x00'
# Unpacking the binary data:
obj2 = unpack(blob, Format)

This library offers extensive functionality beyond basic struct handling. For further details on its powerful features, explore the official documentation, examples, and test cases.

pip install "caterpillar[all]@git https://github.com/MatrixEditor/caterpillar"

pip install "caterpillar[all]@git https://github.com/MatrixEditor/caterpillar/#subdirectory=src/ccaterpillar"

Please visit the Documentation, it contains a complete tutorial on how to use this library.

A list of similar approaches to parsing structured binary data with Python can be taken from below:

• construct
• kaitai_struct
• hachoir
• mrcrowbar

The documentation also provides a Comparison to these approaches.

Distributed under the GNU General Public License (V3). See License for more information.