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Pyevmasm

Pyevmasm is an open-source Python library for assembling Ethereum Virtual Machine (EVM) instructions into opcodes and disassembling EVM bytecode into readable instructions. It includes a command-line utility, a Python API, opcode tables, and selection of instruction sets by fork or block number.

Explore the practical guide ↓

Independent OpenViST project profile, based on linked sources.

Pyevmasm — OpenViST project profile in Developer Tools.
OpenViST project illustration. See the linked sources for product details.
Understand the project

Practical overview

When it fits

Use Pyevmasm when a task calls for low-level EVM instruction assembly, bytecode disassembly, or opcode-table inspection, either from the CLI or within Python.

Who it is for

  • Python developers building EVM bytecode inspection or assembly into their tools.
  • EVM developers who want a command-line way to translate instruction sequences and bytecode.
  • Readers who need to list or inspect opcodes for a supported fork.

Documented uses

  • Disassemble EVM bytecode into readable instructions.
  • Assemble EVM instruction sequences into opcodes.
  • Inspect an opcode table selected by fork or block number.
  • Use Python functions and instruction tables in a bytecode-processing workflow.
Before you choose

Requirements & limits

The repository is public and provides source-install instructions under an Apache-2.0 license. The README requires Python 3.10 or later and documents installation with pip or from source.

  • The CLI supports assembly, disassembly and opcode-table output, with file or standard-input/output handling.
  • Binary input is documented for disassembly and binary output for assembly.
  • The default fork is Byzantium; the CLI also accepts listed fork names or an unsigned block number.
  • The Python API includes instruction tables and functions such as disassemble_hex, disassemble_all and assemble_hex.

Check current requirements in the official documentation. Source-based guidance does not mean OpenViST has run or independently tested this project.

Source-based practical guide

Install Pyevmasm from source

Install the library from its GitHub repository.

Before you start

  • Python 3.10 or later
  • Git
  • pip

Steps

  1. Clone https://github.com/crytic/pyevmasm.

  2. Change into the pyevmasm directory.

  3. Run the command below.

    Documented command
    pip install .

Expected outcome

The repository's source-install instructions install the package from the checked-out project.

Guide limitations

  • These steps cover installation, not a bytecode assembly or disassembly workflow.
Documentation 1 ↗
Evidence and transparency

Sources & review

Official repository ↗
Source record details
Source availability
Active
Sources checked
9 October 2026
Original website title
crytic/pyevmasm · Official homepage title · retained in its source language
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