Mailman 3 April 2013 - Edu-sig

a short essay about programming
by kirby urner Dec. 8, 2022

Dec. 8, 2022

A common "error" (not too serious) that I see in beginning Python (and no doubt other languages, but Python is the one I'm teaching), is having a while condition that appears to put a lid on things, but then the flow all leaks away through break statements, such that the "front door" condition is never revisited. while guess != secret: guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") break else: print("Nope, try again...") What's messed up about the above code is you never really go back to the top in the case where you'd get to leave. Rather, you exit by the back door, through break. So in that case, wouldn't have been simpler and more elegant, even more "correct" (dare I say it) to have gone: while True: # no ifs ands or buts guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") break else: print("Nope, try again...") I see lots of heads nodding, and that could be the end of the matter, but then a next question arises: wouldn't this also be a more correct solution?: while guess != secret: guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") continue # instead of break else: print("Nope, try again...") We're back to having a variable while condition, not a boolean constant, but this time we actually exit by means of it, thanks to continue or... while guess != secret: guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") else: print("Nope, try again...") ... thanks to no continue. This last one is getting a thumbs up, but then I'd pause here and say "continue" can be easier on the eyes. It's unambiguous where it takes you, in contrast to having to scan on down the gauntlet, looking for possibly other open doors. "What happens next" should not require scanning ahead too far. Help us not to get lost. Be a civic-minded coder. I'm thinking of a programming style that advises two things: (a) if you use a while condition that's variable, that's expected to change, then your goal should be to always exit because of that, i.e. that should be your only exit point. Even if some other criterion suggests exiting, you have the option to flip that "lid" at the top, to crack that front door, and bounce the ball out. (b) which is why 'continue' is your friend. You are showing the user where your 'break' statements are, except you don't use "break" statements, as you've given a non-constant condition, and your aim is to make that your ONLY exit point. In short: never use break to exit a while loop unless your condition is while True. Instead, always flip the condition and exit through the font door. However, as soon as I make that rule I can think of good reasons to break it. The other programmers in the room are shaking their heads. Won't we lose information, needed elsewhere in the program, if we "artificially" force a True condition to False. Aren't we, in effect, lying? That concern could be addressed. Keep all the info true, just treat the "lid condition" (it "keeps a lid on it") as a flag. Go ahead and remember the user's guess. allowed = 5 tries = 1 exit = False while not exit: # no other way out guess = int(input("Guess?: ") if guess == secret: print("You guessed it!") exit = True # instead of break continue print("Nope, try again...") tries += 1 if tries == allowed: print("You've maxed out") exit = True continue I think we all understand the main issue: writing reader-friendly code, and rules for doing so. There's something comforting about approaching a while loop and knowing its not a leaky sieve, riddled with back doors, maybe even an exit( ) time bomb. But in the recursion world we want a minimum of two exits usually: when another round is called for versus when we've "hit bottom". Can we have it both ways? Conclusions: Lets not be too hasty with rules of thumb and: Lets keep the reader in mind when writing code. Just because the interpreter knows to compute the flow unambiguously, doesn't mean all ways of writing it are equally reader-friendly. What may seem a gratuitous gesture, an unnecessary flourish, may actually promote reader comprehension of your code, and that should be a goal as much as satisfying the interpreter. Kirby

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Re: [Edu-sig] RurPLE-NG is nice
by Jurgis Pralgauskis April 5, 2014

April 5, 2014

Some updates: - separated Variables Watch and Output panes, to be seen simultaneusly - implemented Breakpoints :) - beta style Todo: - let enter arbitrary watch expressions http://ftp.akl.lt/users/jurgis/python/rurple-NG053.png http://ftp.akl.lt/users/jurgis/python/rurple-ng-dz0-SplitLogVars_and_Breakp… for windows one doesn't need to install python separately, just unzip and run :) http://ftp.akl.lt/users/jurgis/python/RURPLE-NG-0.53%20%5bindependent%20exe… ps.: RurPLE-NG uses py3 unicode_literals, with_statement, division, print_function so code is generally py3 compliant. when wxpy will work well with py3 it shouldn't be too hard to port fully... >> >> just wanted to mention, >> that http://dev.lshift.net/paul/rurple/ >> is a very nice and lightweit PLE. >> >> what I like most (compared to RurPLE) are: >> 1) variables watch list (if it had breakpoints, it would rock :)

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Easy Web Environment to post pupils Python Creations
by Philip Bagge April 1, 2014

April 1, 2014

Dear Colleagues, My Y6 pupils (10-11 year olds) have been creating some simple text based linear adventures using Python. Does anyone know of a way we can play their adventures online? They are not very complicated. You can see the planning here. https://sites.google.com/site/pythoncodecouk/python-adventure Also as a new person to your forum does anyone know of an easy way to search you archives just in case someone has already answered this question. Thanks in advance for any help Phil Bagge -- Primary ICT Advanced Skills Teacher HCC Teacher & IT Manager http://code-it.co.uk

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Python MOOC (massive open online course)
by John Posner June 10, 2013

June 10, 2013

At the nytimes.com site, I came across a reference to this Python course in the comments to Thomas Friedman's latest column: http://blog.topfreeclasses.com/2012/12/an-introduction-to-interactive-pytho… Does anyone have any direct knowledge of this (or any other) Python MOOC? -John

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[ANNC] pynguin-0.14 python turtle graphics application
by Lee Harr May 3, 2013

May 3, 2013

Pynguin is a python-based turtle graphics application. It combines an editor, interactive interpreter, and graphics display area. It is meant to be an easy environment for introducing some programming concepts to beginning programmers. http://pynguin.googlecode.com/ This release adds several user-requested features, including circular arcs, SVG export, and undo. Pynguin is tested with Python 3.2.3 and PyQt 4.9.3 and will use Pygments syntax highlighting if available. Pynguin is released under GPLv3. Changes in pynguin-0.14: Important fixes Other fixes Pynguin API - Added font() to change font for use with write() - Added move parameter for write() - Added align and valign parameters for write() - Added arc() for circular arcs Canvas - Added SVG Export UI - Added ability to use translations - Added (basic) undo capability (ctrl-z) Integrated Editor - Added shortcut (ctrl-w) for removing doc pages - Stop asking for confirmation to remove empty doc page - Stop autosave from modifying empty doc page Integrated Console Examples - Added arc examples

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Learn python programming animated robots
by contacto＠batonbots-ml.net April 26, 2013

April 26, 2013

Hi everyone, I'm bringing to you a personal project made in python. It's free and open-source and ideal to learn how to program playing. BatOnBots-ML is a programming game where each player programs a virtual robot to fight against robots from other players. During a battle, while robots fight, players can see the battle in a 2D interface made in Pygame. Main Features: - Players can choose the your preferred programming language. Currently support: - Python - Java - C/C++ - Multiplayer Online - Players can play over the internet without having to load the robots locally. - Online Leadearboard It is available on: - Linux - Windows Oficial Website: www.batonbots-ml.net To start playing just sign up on the website and follow the Start Guide to help understanding the game. All documentation is on the forum: http://www.batonbots-ml.net/forum/en/index.php?topic=93.msg93#msg93 And you can also see also how to create the first battle and the first robot in these videos: http://www.youtube.com/watch?v=c-H403y7tTI http://www.youtube.com/watch?v=W07Xvd7cf20 Do you think it might be a good learning tool? Hope you enjoy! ;)

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Maintaining the edu-sig page on python.org
by Andre Roberge April 26, 2013

April 26, 2013

Hi everyone, I can no longer maintain the edu-sig page on python.org (and have not done so for a while now). Would anyone be interested in doing it? André

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Re: [Edu-sig] Maintaining the edu-sig page on python.org
by Lee Harr April 26, 2013

April 26, 2013

> In the meantime, it's always a useful thread in edu-sig to brainstorm > the kinds of links we might want. What's new etc.? One thing I think should be added is a link to Portable Python. That is an awesome tool available for both Python 2 and 3. Getting things "installed" at a school can be impossible. Portable Python makes python not just possible, but easy. I was thinking it might be cool to create a Portable Python respin that has a bunch of educational apps, tools, and maybe even lesson plans all built in.

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latest blog re generators & geometry
by kirby urner April 26, 2013

April 26, 2013

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illustrating a class wrapper
by Kirby Urner April 17, 2013

April 17, 2013

def g(x): return x + 2 class Hijack: def __init__(self, f): self.f = g def __call__(self, x): return self.f(x) @Hijack def f(x): return x * x print(f(10)) print(f(100)) The code above shows a decorator, Hijack, that takes a function g from the global namespace and swaps it in for another function f. This might be useful for debugging. You have a new version of a function you want to try and by defining it under another name, yet swapping it in by Hijack, you get to pretend you're using the new version instead. A wrapper function could do the same thing plus take g as an argument: from functools import wraps def g(x): return x + 2 def Hijack2(newf): def decorated(func): @wraps(func) def swap(x): return newf(x) return swap return decorated @Hijack2(g) def f(x): """ 2nd power """ return x * x print(f(10)) # 10 + 2 print(f(100)) # 100 + 2 print(f.__doc__) Executing: 12 102 2nd power Kirby

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