[PYTHON] From the introduction of pyethapp to the execution of contract

Purpose of this article

We have summarized from the introduction of pyethapp for using Ethereum with Python to the execution of contract. In this article, I will introduce up to the point of contracting with Ethereum according to the following flow.

--Building a virtual environment for Python --Installing pyethapp and pyethereum --Install serpent --Compile and execute contract

In addition, the commands executed in this article have been confirmed to work on ubuntu (16LTS) and CentOS (6.9).

Ethereum I will briefly explain the related terms of Ethereum that appear in this article.

What is Ethereum

Ethereum is a Turing-complete contract processing and enforcement platform for blockchain ledgers, with completely independent specifications and implementations rather than Bitcoin duplication. It has a built-in currency called ether and you will be asked to pay when you execute the contract.

What is a contract

The Ethereum blockchain is recorded by the contract. contract is a low-level language, written in Turing complete code, similar to bytecode. A contract is a program that runs on the Ethereum system and allows you to save, pay, receive and save data. It can also act as a decentralized and autonomous software agent to perform computationally unlimited length processing.


-Bitcoin and blockchain technology that supports cryptocurrencies (NTT Publishing)

Python virtual environment construction

Build a Python virtual environment to launch pyethapp.

--Virtual environment construction

$ pip install virtualenv
$ pip install virtualenvwrapper

//Reboot the terminal and virtualenvwrapper.make sh
$ reset

// virtualenvwrapper.Check the location of sh
$ which virtualenvwrapper.sh

$ source /usr/bin/virtualenvwrapper.sh

$ export WORKON_HOME=~/Envs
$ mkdir -p $WORKON_HOME

$ mkvirtualenv pyethapp
$ cd $WORKON_HOME/pyethapp/bin
$ source activate


(pyethapp)$ deactivate


Install pyethapp

pyethapp is a module that implements Ethereum based on Python. In git, only the installation procedure with ubuntu is written, but I was able to install it with CentOS.


$ apt-get install build-essential automake pkg-config libtool libffi-dev libgmp-dev
(pyethapp)$ pip install pyethapp


$ yum groupinstall "Development Tools"
(pyethapp)$ yum install kernel-devel kernel-headers
(pyethapp)$ yum install automake libtool libffi libffi-devel gmp


--There is no related package Error countermeasures (mainly CentOS) http://stackoverflow.com/questions/31508612/pip-install-unable-to-find-ffi-h-even-though-it-recognizes-libffi http://www.techblogistech.com/2012/03/installing-build-essentials-in-centos-make-gcc-gdb/ http://blog.goo.ne.jp/asakurah/e/7f9cdf8cbada8841c388ece8cd421432

Installation of pyethereum

pyethereum is the core library for processing blockchain, ethereum and mining. By installing this in pyethapp, you can use each library.

(pyethapp)$ cd pyethapp
(pyethapp)$ git clone https://github.com/ethereum/pyethereum/
(pyethapp)$ cd pyethereum
(pyethapp)$ python setup.py install


Run pyethapp

The data directory is located in "~ / .config / pyethapp / leveldb" by default.

Account creation

(pyethapp)$ cd pyethapp
(pyethapp)$ pyethapp -d "~/.config/pyethapp/leveldb" account new

//Enter the private key password twice
Password to encrypt private key:
Repeat for confirmation:
Account creation successful
Address: 8d69118ca81b5878ad22d40b701ea9ae88190a60
Id: None

Run on console

Specify testnet in --profile to connect in the test environment. IPython is started by executing it with the console as an argument.

(pyethapp)$ workon pyethapp
(pyethapp)$ pyethapp -d "~/.config/pyethapp/leveldb" --profile testnet run --console

You can use the eth object without importing the library.

$ eth.latest
<CachedBlock(#0 0cd786a2)>

$ eth.latest.get_balance(eth.coinbase)

The pyethereum library can be used on the console by importing it in the same way as IPython.

//Import utilities for Ethereum
$ import ethereum.utils as u

//Import test module
$ import ethereum.tester as t

//Address of test account 1
$ t.a0

$ u.is_numeric(t.a0)

$ u.is_string(t.a0)

//Private key for test account 1(k0)Convert from to address
$ u.privtoaddr(t.k0)

//Create a new blockchain state
$ s=t.state()

//Check all blockchains
$ s.blocks
[<Block(#0 565a32e6)>]

//Increase chains by mining
$ s.mine(n=1)

$ s.blocks
[<Block(#0 50ba5c12)>, <Block(#1 6c0f699b)>]


installation of serpent

serpent is a high-level programming language for writing Ethereum contracts. It is a language specialized in contract programming, which is similar in writing method to Python, allows clean and easy coding, and combines many advantages of low-level languages with a simple programming style. The serpent compiler is written in C ++.


There are two installation methods, but it doesn't matter which one.

--Install from source code

$ git clone https://github.com/ethereum/serpent.git
$ cd serpent
$ git checkout develop
$ make && sudo make install
$ python setup.py install

--Install on pyethapp

(pyethapp)$ git clone https://github.com/ethereum/pyethereum.git
(pyethapp)$ cd pyethereum
(pyethapp)$ git checkout develop
(pyethapp)$ pip install -r requirements.txt
(pyethapp)$ python setup.py install


Create the following serpent file directly under the pyethapp project.


def double(x):
 return (x*2)

Compile using serpent.

$ serpent compile mul2.se
//Bytecode returned

On the pyethapp console, after compilation, the contract can be run consuming gas.

$ d=s.abi_contract("mul2.se")
$ s.block.gas_used
$ d.double(2)
$ s.block.gas_used


Reference summary

--There is no related package Error countermeasures (mainly CentOS) http://stackoverflow.com/questions/31508612/pip-install-unable-to-find-ffi-h-even-though-it-recognizes-libffi http://www.techblogistech.com/2012/03/installing-build-essentials-in-centos-make-gcc-gdb/ http://blog.goo.ne.jp/asakurah/e/7f9cdf8cbada8841c388ece8cd421432

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