pure python什么意思_python-opcua
Pure Python OPC UA / IEC 62541 Client and Server Python 2, 3 and pypy .
http://freeopcua.github.io/, https://github.com/FreeOpcUa/python-opcua
OPC UA binary protocol implementation is quasi complete and has been tested against many different OPC UA stacks. API offers both a low level interface to send and receive all UA defined structures and high level classes allowing to write a server or a client in a few lines. It is easy to mix high level objects and low level UA calls in one application.
Most low level code is autogenerated from xml specification, thus adding missing functionnality to client or server is often trivial.
Using Python > 3.4 the dependencies are cryptography and dateutil. If using python 2.7 or pypy < 3 you also need to install enum34, trollius(asyncio), and futures(concurrent.futures), with pip for example.
coveryage.py reports a test coverage of over 90% of code, most of non-tested code is autogenerate code that is not used yet.
uadiscover (find_servers, get_endpoints and find_servers_on_network calls)
uals (list children of a node)
uahistoryread
uaread (read attribute of a node)
uawrite (write attribute of a node)
uasubscribe (subscribe to a node and print datachange events)
uaclient (connect to server and start python shell)
uaserver (starts a demo OPC UA server)
tools/uaserver --populate --certificate cert.pem --private_key pk.pem
Client: what works:
connection to server, opening channel, session
browsing and reading attributes value
gettings nodes by path and nodeids
creating subscriptions
subscribing to items for data change
subscribing to events
adding nodes
method call
user and password
history read
login with certificate
communication encryption
removing nodes
Tested servers: freeopcua C++, freeopcua Python, prosys, kepware, beckoff
Client: what is not implemented yet
localized text feature
adding some missing modify methods
XML protocol
Server: what works:
creating channel and sessions
read/set attributes and browse
gettings nodes by path and nodeids
autogenerate addres space from spec
adding nodes to address space
datachange events
events
methods
basic user implementation (one existing user called admin, which can be disabled, all others are read only)
encryption
certificate handling
removing nodes
history support for data change and events
Tested clients: freeopcua C++, freeopcua Python, uaexpert, prosys, quickopc
Server: what is not implemented
alarms
XML protocol
views
localized text features
better securty model with users and password
adding some missing modify methods
Server: Running on a Raspberry Pi
Setting up the standard address-space from XML is the most time-consuming step of the startup process which may lead to long startup times on less powerful devices like a Raspberry Pi. By passing a path to a cache-file to the server constructor, a shelve holding the address space will be created during the first startup. All following startups will make use of the cache-file which leads to significantly better startup performance (~3.5 vs 125 seconds on a Raspbery Pi Model B).
Development
Code follows PEP8 apart for line lengths which should be max 120 characters and OPC UA structures that keep camel case from XML definition.
All protocol code is under opcua directory
opcua/ua contains all UA structures from specification, most are autogenerated
opcua/common contains high level objects and methods used both in server and client
opcua/client contains client specific code
opcua/server contains server specific code
opcua/utils contains some utilities function and classes
opcua/tools contains code for command lines tools
schemas contains the XML and text files from specification and the python scripts used to autogenerate code
tests contains tests
docs contains files to auto generate documentation from doc strings
examples contains many example files
tools contains python scripts that can be used to run command line tools from repository without installing
Running tests:
python tests.py
Coverage
coverage run tests.py
coverage html
firefox htmlcov/index.html