Mailman 3 August 2007 - Edu-sig

Open Minds Conference
by Nicholas Wheeler 14 Aug '07

14 Aug '07

This isn't very python related, but it is open source software in education related....I'm guessing some of you on this list would love to speak as a presenter at this conference on the work you do using open source tools in education..... http://openmindsconference.org -- Nicholas Wheeler Systems Administrator Development InfoStructure

1 0

snakes ad infinitum
by Dean Goodmanson 09 Aug '07

09 Aug '07

Greetings Pythoneers, I pondered far and wide which Python SIG might find this shirt most captivating and have drawn to a near conclusion that the EDU-SIG'ers could stomach it. Even if this device resembles a spiced ham product. http://shirt.woot.com/Friends.aspx?k=3656 Be well and never tire the CP4E quest. Looking forward to seeing you in Chicago for PyCon `08 next March. Anyone need a talk topic? http://www.google.com/search?q=CP4E+prosumer -Dean ____________________________________________________________________________________ Moody friends. Drama queens. Your life? Nope! - their life, your story. Play Sims Stories at Yahoo! Games. http://sims.yahoo.com/

2 1

When am I the same age as my dog?
by kirby urner 08 Aug '07

08 Aug '07

I may have posted about this awhile back, but it came up as a real question for a man wanting to party the day his dog caught up and passed him in age, assuming one human year = seven dog years. It makes a fun Python program as it involves dates, which are notoriously problematic. Hint: Julian dates might come in handy, plus don't forget leap years. Another posing of the problem: Every day I live counts as 1 day, every day a dog lives counts as 7. Given a dog born later than myself (date), and my birthday (date), on which day will my dog and I have the same number of days to our credit (date)? I.e. date samecount ( date dog_bday, date my_bday ) Note: my newest gig involves teaching SQL using Python in shell mode to start (import MySQLdb **), per my standard pedagogy: http://worldgame.blogspot.com/2007/08/sa-pedagogy.html This courseware is proprietary by mutual consent, so I won't be saying much more about it here (or anywhere). Just more of the usual day job. Kirby ** typical student/teacher interface: """ kirby@dell:~$ ssh [xxx] [xxx] password: Last login: Wed Aug 8 11:33:46 2007 from [yyy] [prompt ~]$ python2.5 Python 2.5.1 (r251:54863, Jul 17 2007, 14:30:01) [GCC 3.4.6 20060404 (Red Hat 3.4.6-8)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import MySQLdb >>> dir(MySQLdb) ['BINARY', 'Binary', 'Connect', 'Connection', 'DATE', 'DATETIME', 'DBAPISet', 'DataError', 'DatabaseError', 'Date', 'DateFromTicks', 'Error', 'FIELD_TYPE', 'ImmutableSet', 'IntegrityError', 'InterfaceError', 'InternalError', 'MySQLError', 'NULL', 'NUMBER', 'NotSupportedError', 'OperationalError', 'ProgrammingError', 'ROWID', 'STRING', 'TIME', 'TIMESTAMP', 'Time', 'TimeFromTicks', 'Timestamp', 'TimestampFromTicks', 'Warning', '__all__', '__author__', '__builtins__', '__doc__', '__file__', '__loader__', '__name__', '__path__', '__revision__', '__version__', '_mysql', 'apilevel', 'connect', 'connection', 'constants', 'debug', 'escape', 'escape_dict', 'escape_sequence', 'escape_string', 'get_client_info', 'paramstyle', 'release', 'result', 'server_end', 'server_init', 'string_literal', 'thread_safe', 'threadsafety', 'times', 'version_info'] """

1 0

Python types, iterators in particular
by kirby urner 05 Aug '07

05 Aug '07

Speaking of types, I'm not seeing a generic 'iterator type' in the types module. Then we have all these special types for iterable objects: >>> type(xrange(10)) <type 'xrange'> >>> type((i for i in range(10))) <type 'generator'> >>> type(enumerate((1,2,3,4))) <type 'enumerate'> >>> type(iter([1,2,3,4,5])) <type 'listiterator'> >>> type(iter((1,2,3))) <type 'tupleiterator'> Noting: """ (In retrospect, it might have been better to go for __next__() and have a new built-in, next(it), which calls it.__next__(). But alas, it's too late; this has been deployed in Python 2.2 since December 2001.) """ [ http://www.python.org/dev/peps/pep-0234/ ] Is this part of what's fixed in Python 3.0 then? Plus there'll be some type integration under the concept if 'iterator type'? I've heard Guido's latest 3.0 talk twice now, and that's the impression I'm left with. Background to this question (writing about Python 3.0 on another list): """ The details are interesting too. What's been emerging in computer science is this notion of "lazy evaluation" akin to "just in time" in many dimensions (another important meme). In Python, this was foretold by xrange, a prophetic __builtin__ in retrospect. xrange will be simply range in Python 3.x. What did xrange foretell? Lazy evaluation. Instead of pre-allocating gobs of memory, just save the algorithm for getting the *next* in the sequence, only deliver when specifically asked. Constructs such as 'for p in primes:' don't seem so strange any more, because 'primes' isn't an infinite chunk of memory, so much as a factory for a sequence of values, to be delivered conveyor belt style, but only when a .next() button is pressed. All that __next__ button pushing takes time, and in the mean time, Python is off doing other things. However, this notion of an "iterable" (source of next values) wasn't so clear in the early days of Python. xrange foretold it, but now we have explicit generators and generator expressions. We've since elevated 'iterable' to a known type (a 'duck type' as we say) and return it more consistently as such, and not just by xrange (soon to be just range, taking the place of the old memory pre-allocating version). These innovations were just not conceived of in the earliest Pythons. So rather than focusing on Guido's "mistakes" (aka "regrets"), we have the option to just talk about advances, and Python's amazing ability to adopt them, cleanly and intelligently (a tribute to its namesake). """ Kirby

1 0

Re: [Edu-sig] interactive vs compiled from file
by John Posner 05 Aug '07

05 Aug '07

Nice discussion! Here's my suggestion: if the user types an expression that returns a value, have IDLE echo the return value annotated with its type, and with "<<<" as a prefix. Reversing the direction of the angle brackets is a neat (IMHO) way to remind the user of the concept of "return value". Examples: ############################################# set it up >>> import sys >>> sys.displayhook = show_expression_value ############################################# show how it works >>> 23 + 45 - 31 <<< 37 (INTEGER expression value) >>> 2/3.0 <<< 0.67 (FLOAT expression value) >>> 'hi' + 'there' <<< 'hithere' (STRING expression value) >>> def f(inp): return inp >>> f('func arg') <<< 'func arg' (STRING expression value) >>> f(2 + 3 + 4) <<< 9 (INTEGER expression value) ############################################# quiet if return value is None >>> a = 2 + 3 + 4 >>> a = f(4.56789) Here's my implementation: def show_expression_value(val): """ Show expression value or function return value in IDLE. Deploy this function with: sys.displayhook = show_expression_value """ if type(val) is type("hello"): displayme = "'%s'" % val print "<<< %-15s (STRING expression value)" % displayme elif type(val) is type(1): displayme = "%d" % val print "<<< %-15s (INTEGER expression value)" % displayme elif type(val) is type(1.0): displayme = "%.2f" % val print "<<< %-15s (FLOAT expression value)" % displayme # TO DO: more "elif"s for other value types

2 1

Free Wingware version for students
by kirby urner 04 Aug '07

04 Aug '07

Probably a lot of you got this annoucement already: http://wingware.com/wingide-101 Free, not open source, still in beta. Good Python editor with integrated shell mode. I'm planning to play with it -- haven't yet. Might use it in my next Saturday Academy class. Kirby

1 0

interactive vs compiled from file
by Michael Tobis 04 Aug '07

04 Aug '07

One problem I have consistently had with beginners is in explaining the difference between how the interpreter produces output without an explicit 'print' statement (producing the str() of the last evaluated expression) and how python run from a file does not. This is perfectly natural and useful for an experienced user, but it is awkward and confusing for the beginner, who has enough of a cognitive load just trying to track all the pieces. This leads to two (well, four) questions: 1) How have you folks addressed this problem in your beginning classes? Do you find it causes difficulties? 2) Would it be difficult to provide an alternative interpreter that produced nothing unless you asked it to print? Would this be a good idea? thanks mt

4 14

Interesting thread...
by kirby urner 03 Aug '07

03 Aug '07

For CS teachers interested in matters Pythonic: http://lambda-the-ultimate.org/node/1840 Kirby

1 2