pyasm 1.1.5

Description:

pyasm 1.1.5

PyASM
PyASM is a python library designed to help modify bytecode in a somewhat easy manner.
The API design is loosely based on objectweb:asm for Java.
Features
Deconstruct code objects
You can use the asm.Deserializer class to convert a code object into a list of opcodes
>>> from asm import *
>>>
>>> def my_function(x: int = 1) -> int:
... if x > 20:
... return x / 20
... return x
...
>>> deserializer = Deserializer(my_function.__code__)
>>> deserializer.deserialize() # Below is formatted for readability
[
LOAD_FAST(id=124, arg='x'),
LOAD_CONST(id=100, arg=20),
COMPARE_OP(id=107, arg=4),
POP_JUMP_IF_FALSE(id=114, arg=Label(0x7fd2fbeb0d60)),
LOAD_FAST(id=124, arg='x'),
LOAD_CONST(id=100, arg=20),
BINARY_TRUE_DIVIDE(id=27, arg=0),
RETURN_VALUE(id=83, arg=0),
Label(0x7fd2fbeb0d60),
LOAD_FAST(id=124, arg='x'),
RETURN_VALUE(id=83, arg=0)
]

Construct code objects
Conversely, you can also turn a list of opcodes into a code object using asm.Serializer
>>> from asm import *
>>>
>>> dummy = lambda x: None
>>> serializer = Serializer([ # Bytecode for `return x * 20`
... LOAD_FAST("x"),
... LOAD_CONST(20),
... BINARY_MULTIPLY(),
... RETURN_VALUE()
... ], dummy.__code__)
>>> dummy.__code__ = serializer.serialize()
>>> dummy(10)
200

Jumps
A big issue when modifying bytecode is jumps. We solve this by using asm.Label:
>>> from asm import *
>>> lbl = Label()
>>> ops = [
... LOAD_CONST(10),
... LOAD_CONST(20),
... COMPARE_OP("<"),
... POP_JUMP_IF_FALSE(lbl), # jump to where lbl is located
... LOAD_CONST(True),
... RETURN_VALUE(),
... lbl, # jump to here
... LOAD_CONST(False),
... RETURN_VALUE()
... ]

This way, no matter how many instructions you place between the jump and the label, it will always resolve correctly.
Installing
To install PyASM, you can just use pip:
pip install pyasm

License
PyASM is licensed under MIT.