WFE603 Programming in Python Rob Faludi Collaborative Strategy Leader

Session Overview Problem Statement Python Programming Language (v. 2.4) Python on Digi devices Digi ESP

The Problem Putting application intelligence in the right places Writing simply Writing experimentally Writing powerfully

Where’s Your Application?

Open-source, flexible language that puts decision-making smarts on a gateway Very simply to write basic code Easy to experiment interactively Powerful extensions Broad support

High-level Readable Dynamically typed Automatic memory management Scripting, OOP, functions Extensible Powerful Portable Free

Zen of Python Beautiful is better than ugly. Explicit is better than implicit. Simple is better than complex. Complex is better than complicated. Flat is better than nested. Sparse is better than dense. Readability counts. Special cases aren't special enough to break the rules. Although practicality beats purity. Errors should never pass silently. Unless explicitly silenced. In the face of ambiguity, refuse the temptation to guess. There should be one-- and preferably only one --obvious way to do it. Although that way may not be obvious at first unless you're Dutch. Now is better than never. Although never is often better than *right* now. If the implementation is hard to explain, it's a bad idea. If the implementation is easy to explain, it may be a good idea. Namespaces are one honking great idea -- let's do more of those!

Less is more – Less to type – Less to debug – Less to maintain Productivity

Lots of Resources Online – Python.org ( – Dive Into Python ( – Python Challenge ( Books – Learning Python by Mark Lutz – Programming Python by Mark Lutz – Python Cookbook by Alex Martelli, Anna Martelli Ravenscroft, David Ascher

A basic program def hello(): """Prints a salutation to the user""" # Say hello print "Hello World!" if __name__ == "__main__": hello() Note that indentation dictates structure, not keywords or special tokens.

Really basic print "Hello World!"

Python is about getting work done print "Hello World!" print 2+2 foo="bar" print foo

Indentation Matters if 1+1==2: print "answer correct!" print "you did math!" if 1+1==3: print "answer correct" print "you did math!"

Core Data Types Numbers Strings Lists Dictionaries Tuples Files

Data types – Scalars Numbers – Three types (int, float and long) – Varying representations (10, 0xa, 012) – Don't worry too much about type (except division) – 5 /2 = 2 – 5.0 / 2 = 2.5 – from __future__ import division bool – Values ( True and False ) None

Container Objects Sequences – Strings: mystring ="abcdefg" – Lists: foo=[1, 'a', None] – Tuples: bar=(1, 'a', None) (immutable) Mapping – Dictionaries: moof={"a": True, 42: 7}

Strings Normal – "Hello\nThere" (allows escapes) Triple-quoted (preserves entered text) """Hello There""" Raw – r"Hello\nThere" (escapes ignored) Unicode – u"\u0496"( inserts Җ) – Allows unicode escapes, creates unicode strings, a different type Many native operations plus normal immutable sequence operations

dir shows available attributes >>> f= 37.1 >>> g="hello" >>> dir(f) ['__abs__', '__add__', '__class__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__eq__', '__float__', '__floordiv__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__int__', '__le__', '__long__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__nonzero__', '__pos__', '__pow__', '__radd__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rmod__', '__rmul__', '__rpow__', '__rsub__', '__rtruediv__', '__setattr__', '__str__', '__sub__', '__truediv__'] >>> dir(g) ['__add__', '__class__', '__contains__', '__delattr__', '__doc__', '__eq__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__getslice__', '__gt__', '__hash__', '__init__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__str__', 'capitalize', 'center', 'count', 'decode', 'encode', 'endswith', 'expandtabs', 'find', 'index', 'isalnum', 'isalpha', 'isdigit', 'islower', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'replace', 'rfind', 'rindex', 'rjust', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill’]

Conditional Execution if : elif : else : There is no goto or case statement in Python

Loops for in : while : Variations: break and continue affect looping pass can act as a placeholder (x)range(i[, j[, k]]) is extremely useful for for statements

Functions def arg_info(arg=42, *pos_args, **kw_args): """Doc-string""" if (arg == 42): print "arg has default value" # Print positional arguments for i in len(pos_args): # Use string formatting operator print "Positional argument %d is %v" % (i, pos_args[i]) print "Keyword arguments" for key in kw_args.keys(): print "\t", key, ": ", kw_args[key] return len(pos_args) + len(kw_args)

Modules We already have seen one # hello.py def hello(): """Prints a salutation to the user""" # Say hello print "Hello World!" if __name__ == "__main__": hello() import hello hello.hello()

Importing Styles – from import – import as Uses sys.path to find

Exceptions and Error Handling class ItCantWork(Exception): pass def no_work(): raise ValueError try: no_work() except ValueError, e: # handle exception does_work() else: raise ItCantWork

Homework Classes Generators Iterators List comprehensions The standard library Lots of other useful things…

Where do I configure Python on the Digi device? – Applications -> Python in the WebUI – Manage scripts and module files on the device – Configure Python scripts to run automatically on boot – Python in iDigi Manager Pro – Manage scripts and module files on the device – Configure Python scripts to run automatically on boot – Python command line tools – set python – Configure automatic start with added options – python – Run scripts manually, or enter an interactive session Using Digi Python

Plain Text Files use.py extension upload files iDigi web UI command line interface Putting Files on the Device

Check the Box iDigi web UI command line interface Command Line Launch from CLI: set python or from within Python: import Launching a Program

Purpose: Configures Python programs to execute on device boot. Syntax: set python [range=1-4] [state={on|off}] [command=filename,args] Options: range=1-4 Range specifies the index or indices to view or modify with the command. state={on|off} When the state is set to on, the specified command is run when the device boots. command=filename,args The program filename to execute and any arguments to pass with the program, similar to the arguments for the python command. The command option allows for programs to be run from a TFTP server; however, this usage is not recommended. If there are spaces to provide arguments, make sure to wrap the entire command in quotation marks. set python

terminal% telnet Trying Connected to Escape character is '^]'. #> python >>> Running Interpreter

Monitoring the System Management -> Connections For monitoring only, can't disconnect Python activity Equivalent functionality in the CLI is the who command

Checking Resources (Memory) The memory of the system is all the memory there is (no virtual memory), use it wisely. The rest of the system uses memory as well, leave some for it (~ k at least)

Checking Resources (Sockets) 128 max in the entire system

Garbage Collection Simplest: – Run gc.collect() as often as "you find necessary". Tune thresholds (gc.set_threshold) – "correct" values vary widely per application Don't use __del__ methods If you must, break cycles manually by examining gc.garbage periodically and using your object knowledge to resolve the cycle

Viewing Debug Output #> set trace state=on mask=printf:* All sys.stdout and sys.stderr output from your script will be redirected to the console that ran trace.

Digi Python

XBee ® Sockets Creation: from socket import * s = socket(AF_XBEE, SOCK_DGRAM, XBS_PROT_TRANSPORT) XBee sockets are datagram sockets like UDP Maximum packet length depends on radio technology and configuration Address format: (address_string, endpoint, profile_id, cluster_id) zigbee/zb_ex1_hello.py, zb_ex2_rw.py

XBee Module ddo_command(addr_extended, id[, param, timeout, order=False, apply=True) ddo_set_param(…) ddo_get_param(…) – No param argument Get/set DDO parameters on XBee modules – addr_extended – Address of node to configure – id – Two letter string identifying parameter – param – New value to set for ddo_command or ddo_set_param – timeout – Max time to wait for response – order – Force this request not to run concurrently – apply – Make changes active (Same as "AC" id) Returns: ddo_command and ddo_get_param return binary string configuration value. ddo_set_param returns boolean success. All versions throw an exception if they cannot reach the radio.

XBee (cont…) get_node_list( ) -> list of node objects Performs device discovery – refresh False: returns the gateways cache of nodes. True: Blocks to perform fresh discovery Node object attributes – type: One of coordinator, router or end – addr_extended, addr_short: Address representations – addr_parent: Parent's short address – profile_id, manufacturer_id: Identifying characteristics – label: Nodes 'NI' parameter – device_type: Nodes 'DD' parameter zigbee/zb_ex4_disc.py

File system Path structure is / System volume is WEB Python modules go in WEB/python Directory listing/traversal may be limited – listdir, mkdir will be available in FW version 2.9 USB volumes progress A, B,... – Not guaranteed to enumerate the same each boot Python file objects work completely.

Digicli Module import digicli digicli.digicli( ) -> (status, output) Run a CLI command – cmd – Command to run Returns – status – False if command failed – output – list of output lines from execution

Perform a Network Node Discovery # Perform a node discovery and print out # the list of discovered nodes to stdio. # import the zigbee module into its own namespace import zigbee # Perform a node discovery: node_list = zigbee.getnodelist() # Print the table: print "%12s %12s %8s %24s" % \ ("Label", "Type", "Short", "Extended") print "%12s %12s %8s %24s" % \ ("-" * 12, "-" * 12, "-" * 8, "-" * 24) for node in node_list: print "%12s %12s %8s %12s" % \ (node.label, node.type, node.addr_short, node.addr_extended)

Use DDO to Read Temperature from XBee Sensor # Collect a sample from a known XBee Sensor adapter # and parse it into a temperature. # import zigbee and xbee_sensor modules: import zigbee import xbee_sensor # configure known destination: DESTINATION="[00:13:a2:00:40:0a:07:8d]!" # ensure sensor is powered from adapter: zigbee.ddo_set_param(DESTINATION, 'D2', 5) zigbee.ddo_set_param(DESTINATION, 'AC', '') # get and parse sample: sample = zigbee.ddo_get_param(DESTINATION, '1S') xbee_temp = xbee_sensor.XBeeWatchportT() xbee_temp.parse_sample(sample) print "Temperature is: %f degrees Celsius" % (xbee_temp.temperature)

Digicli Example import digicli status, output = digicli.digicli('show net') if status: for line in output: if line.find('MAC Address') >= 0: l = line.split(':') print "".join(l[1:]).strip()import digicli digicli.digicli( ) -> (status, output)

The Digi ESP

An IDE used across several product lines, built on top of Eclipse Facilitates development with Digi products Distributed as a built-in product (not as plug-ins) Powerful editing capabilities (syntax highlight, auto completion, syntax verification, …); Code builders and checkers; Integrated symbolic debugger Example/Project wizards Configuration tools Extended through custom plug-ins to provide a better integration with our products Bundled with other components needed like JVM, Python interpreters, etc Multiplatform (runs on MS Windows, Linux and Mac)

The Digi ESP

ESP flavors

Digi ESP for Python Complete and simplified development process: – Easy-to-use project wizards – Python source code and Smart iDigi Dia Editor – Build management – Remote launch/debug – Application deployment Built-in iDigi support Full integrated help with interactive tutorials Additional tools: – Device discovery (USB, LAN and iDigi) – Remote file explorer – Channel explorer – Terminal consoles – Package manager

Package Manager Server Digi Internet Digi ESP for Embedded Linux Digi ESP for NET+OS Digi ESP for Python Package Manager Digi ESP software distribution/upgrade plug-in Allows the access to the different software packages available on the PkM server, available for that specific ESP flavor, accordingly to the privileges provided by the installed PkM license(s) Packages are created by Digi engineers which are later posted to the Package Manager server, making them available to all Digi ESP users Package Types: – New features – Fixes – Documentation – Updates – Other

Getting ESP

Using ESP connecting devices Hello World SMTP HTTP Dia Example

Digi Python Samples

Connect a Device

Hello World """\ Hello World! demo for Digi devices This example prints out a "Hello World!" message to stdout. """ import sys, os print "Hello World!"

SMTP Alarm SMTP_Server = " .mydomain.com" #hostname of the SMTP server sender_ = #The sender's address recipient_ = #The destination address subject = "Value Detect test" #Subject of the msg_format = 'The value is now: %s' #The body of the , the sample will #replace the %s in this message. print "Creating alarm" _alarm = alarm.SMTPAlarm(alarm_function, msg_format, debounce_function, SMTP_Server, sender_ , recipient_ , subject)

Fetch Web Page "def main(): # Open the web page. fhandler = urllib.urlopen(WEB_PAGE) # Print some details about the page retrieved page_info = fhandler.info() print "Retrieved '%s'\r\n" %fhandler.geturl() for item in page_info.items(): print "%s : %s" %(item[0], item[1]) print "\r\nPage content:" # Start reading and printing the content of the web page. while True: data = fhandler.read(1024) if len(data) == 0: break sys.stdout.write(data)

Dia

Using Digi Python Where can I get more information? – Digi developer Wiki ( – "Digi Python Programmer's Guide" in particular – Digi support forum ( – Drop-In Networking -> Software -> Python What version of Python should I use? – Python 2.4 for Digi NDS devices. – Python 2.7 for Digi X2E devices.

THANK YOU! Rob Faludi