🌐 Mailman 3 December 2014 - Python-list - python.org

Re: Hello World
by Steven D'Aprano Dec. 23, 2014

Dec. 23, 2014

Tony the Tiger wrote: > On Sat, 20 Dec 2014 23:57:08 +1100, Steven D'Aprano wrote: > >> I am in total awe. > > I'm not. It has no real value. Write your code like that and you'll soon > be looking for a new job. Awww, did da widdle puddy tat get up on the wrong side of the bed this morning? :-) Obviously you don't write obfuscated code like this for production use, except in such cases where you deliberately want to write obfuscated code for production use. Any beginner with 3 seconds experience with Python can write: print "Hello World" But being able to write obfuscated code to that degree displays real skill and understanding of the language, and a great deal of patience and "stick with it"-ness, all of which are valuable work skills. -- Steven

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Re: Hello World
by Roy Smith Dec. 23, 2014

Dec. 23, 2014

In article <mailman.17133.1419276169.18130.python-list(a)python.org>, Tim Chase <python.list(a)tim.thechases.com> wrote: > On 2014-12-22 19:05, MRAB wrote: > > On 2014-12-22 18:51, Mark Lawrence wrote: > > > I'm having wonderful thoughts of Michael Palin's favourite Python > > > sketch which involved fish slapping. > > > > > Well, ChrisA _has_ mentioned Pike in this thread. :-) > > But you know he does it just for the halibut... > Are you guys fishing for complements?

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Re: Program calling unwanted functions
by sohcahtoa82＠gmail.com Dec. 23, 2014

Dec. 23, 2014

On Monday, December 22, 2014 3:57:31 PM UTC-8, Dave Angel wrote: > On 12/22/2014 06:48 PM, Ian Kelly wrote: > > On Dec 22, 2014 2:37 PM, "Dave Angel" <davea(a)davea.name> wrote: > >> > >> I'll pick on one function first, called instructions(). If the user > > types something invalid, you print "Invalid input." and call the function > > again. In this case, because the call is at the end, no harm is usually > > done, but it would be tricky to explain why. If the user happened to type > > the wrong input 1000 times, you'd hit a recursion limit and crash, but > > that's unlikely unless you have a very stubborn user. > > > > Point of interest, Python (or at least CPython) doesn't optimize tail-call > > recursion, so in fact this sort of unbounded recursion (a "stack leak", if > > you will) is equally bad no matter where it appears in the function. > > > > Which is exactly why I mentioned the recursion limit of about 1000. > > > -- > DaveA Python 2.7.3 (default, Dec 4, 2012, 17:28:13) [GCC 4.4.5 20110214 (Red Hat 4.4.5-6)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> def test(t): ... print(t) ... test(t+1) ... >>> test(1) 1 2 3 4 <snip> 998 999 Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in test File "<stdin>", line 3, in test File "<stdin>", line 3, in test <snip> File "<stdin>", line 3, in test File "<stdin>", line 3, in test RuntimeError: maximum recursion depth exceeded Huh...there actually is a limit of about 1,000. I'm assuming this is hard-coded? I did a similar test with Java a while back and was getting different results every time.

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Program calling unwanted functions
by Luke Tomaneng Dec. 22, 2014

Dec. 22, 2014

Hello to all those in this forum, My code seems to have a mind of its own. I have been writing a program to reenact the "Twenny Wun" Vine video, and it seems to be activating functions without me calling them. Here is the script: def kid(): print "Cameraman: You stupid." kid1 = raw_input("Kid: ") if kid1.lower() == "no im not" or kid1.lower() == "no i'm not.": print "Cameraman: What's nine plus ten?" kid2 = raw_input("Kid: ") if kid2.lower() == "twenny wun" or kid2.lower() == "twenty-one" or kid2.lower() == "twenty one" or kid2 == "21" or kid2.lower() == "twenny one": print """Cameraman: You stupid. Ending program... """ else: print "That is not the right quote." kid() else: print "That is not the right quote." kid() def cameraman(): cameraman1 = raw_input("Cameraman: ") if cameraman1.lower() == "you stupid": print "Kid: No I'm not." cameraman2 = raw_input("Cameraman: ") if cameraman2.lower() == "whats 9 + 10" or cameraman2.lower() == "whats nine plus ten": print "Kid: Twenny wun" cameraman3 = raw_input("Cameraman: ") if cameraman3.lower() == "you stupid": print "Ending program..." time.sleep(2) else: print "That is not the right quote." cameraman() else: print "That is not the right quote." cameraman() else: print "That is not the right quote." cameraman() def perspective(): perspective_request = raw_input("Do you want to be the cameraman or the kid? (type the one you want): ") if perspective_request == "cameraman": cameraman() if perspective_request == "kid": kid() else: print "Invalid input." perspective() def instructions(): instructions_request = raw_input("Do you want instructions? (type 'yes' or 'no' without the quotes): ") if instructions_request == "no": perspective() if instructions_request == "yes": print "This is a reenactment of the 'Twenny Wun' Vine. You can type in the empty space to the right of each ':,' then press [return]. Don't use punctuation." perspective() else: print "Invalid input." instructions() instructions() The "cameraman" function restarts itself when it ends, and the "kid" function calls "instructions()." Does anyone know why?

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TypeError: unhashable type: 'list'
by ronald.kevin.burton＠gmail.com Dec. 22, 2014

Dec. 22, 2014

I am getting an exception that the traceback looks like: ------------------------------------------------------------ Traceback (most recent call last): File "C:\Projects\QA\robot_20141103\resources\assessment_utilities.py", line 29, in create_new_project program = customer.add(program_code) File "C:\Projects\QA\robot_20141103\resources\assessment_customer.py", line 589, in add program = ProgramMaker.Code2Program(program_code, self) File "C:\Projects\QA\robot_20141103\resources\programmaker.py", line 25, in Code2Program 'ASSESS_PPL' : PPL(customer) File "C:\Projects\QA\robot_20141103\resources\ppl.py", line 20, in __init__ MeasureMaker.Code2Measure('Furnace Whistle', self) TypeError: unhashable type: 'list' ------------------------------------------------------------ My problem is that I am not sure what the problem is. I can check the type of 'self' which is an object and the string 'Furnace Whistle' is obviously not a list. The static function 'MeasureMaker.Code2Measure' is a simple factory: class MeasureMaker: def Code2Measure(measure_code, core): try: return { ... 'Furnace Whistle': FurnaceWhistle(core) }[measure_code] except KeyError as error: return None Code2Measure = staticmethod(Code2Measure) What is the 'list' that is in the exception? Or how do I find out? Thank you. Kevin

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Re: List Comprehensions
by Steven D'Aprano Dec. 22, 2014

Dec. 22, 2014

Chris Angelico wrote: > On Mon, Dec 22, 2014 at 8:21 PM, Steven D'Aprano > <steve+comp.lang.python(a)pearwood.info> wrote: >> If the called function has side-effects, a list comp is not a good >> solution. > > Hmm. I'm not so sure about that. Side effects are fine in a list comp, > as long as you're making use of the return values. For instance, if > you have a function that inserts a record to a database and returns > the new ID, you could reasonably use a list comp to save a bunch of > records and get a list of IDs for subsequent use. I hear what you are saying, but a list comprehension is a functional idiom. To mix functional and procedural idioms in the one expression is rather icky. Better to use one or the other but not both simultaneously. I'll accept that this is a weak recommendation though. -- Steven

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Re: Hello World
by Grant Edwards Dec. 22, 2014

Dec. 22, 2014

On 2014-12-21, Tony the Tiger <tony(a)tiger.invalid> wrote: > On Sat, 20 Dec 2014 23:57:08 +1100, Steven D'Aprano wrote: > >> I am in total awe. > > I'm not. It has no real value. Write your code like that and you'll soon > be looking for a new job. I think you'll find that people who know enough to write code like that only do it for entertainment purposes. -- Grant

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Re: List Comprehensions
by Rustom Mody Dec. 22, 2014

Dec. 22, 2014

On Monday, December 22, 2014 8:37:50 PM UTC+5:30, Chris Angelico wrote: > On Tue, Dec 23, 2014 at 1:58 AM, Rustom Mody wrote: > > If you consider side-effecting comprehensions as kosher, > > then a next conclusion is naturally going to be that > > multiple generator comprehensions are confusing and therefore > > not kosher -- a very unfortunate conclusion IMHO. > > Why does that follow? What has that to do with side effects? A comprehension means two things 1. There is the standard de-sugaring in terms of for-loops given in the docs that Steven repeated above. 2.There is this picture (needs to be seen in fix-pitch font) [f(x) for x in [x₁ x₂ x₃ … xₙ]] means [x₁ x₂ x₃ … xₙ] ↓ ↓ ↓ ↓ [fx₁ fx₂ x₃ … fxₙ] There are not just two different ways of writing that for-loop -- upwards and downwards -- there are n! ways. And even that assumes that each arrow is atomically and sequentially performed. An assumption quite ok for a sequential machine completely unnecessary for a programmer. Give up that assumption and the ways are infinite IOW the second view is more abstract and programmer friendly than the first in the same way that saying the C expression "x+1" "Adds 1 to the variable x" rather than saying "Its the C version of add 1, %eax" [Why not inc %eax ?] And this despite the fact that mathematical integers and real are rather far removed from C's int and float. IOW white lies are preferable to exact precise gobbledygook. If the semantics of the comprehension depends on the order of the arrows, the comprehension is screwed Shorter technological answer: In Haskell a side-effecting function gets a monadic type -- the type carries the moniker "I am side-effecting" and so it cant be put in to a comprehension without type errors. Now python's type system cannot do what Haskell's can [for better or worse is another matter -- a strong type system can be neat or a pain] Considering that python's comprehensions are cloned from Haskell, it seems fair that Haskell's formal strictures be passed on to beginners at least informally

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Re: Hello World
by Steven D'Aprano Dec. 22, 2014

Dec. 22, 2014

Skip Montanaro wrote: > On Mon, Dec 22, 2014 at 9:22 AM, Steven D'Aprano < > steve+comp.lang.python(a)pearwood.info> wrote: >> Don't try this at home! >> >> >> # download_naked_pictures_of_jennifer_lawrence.py >> import os >> os.system("rm ――rf /") > > And because Steven *knows* some fool will "try this at home", he cripples > the rm command. Now where's the fun in that? :-) Ah, I'm just a big softie :-) -- Steven

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List Comprehensions
by Ganesh Pal Dec. 22, 2014

Dec. 22, 2014

Hi , (a) I was trying to reduce the below piece of code using List comprehension ? Any suggestion please let me know for opt in options: opt['result'] = Queue.Queue() tmp_thread = pause.Thread(opt) threads.append(tmp_thread) tmp_thread.start() (b) * Is there anything that I need to consider while using list comprehension with threads ?* Regards, Ganesh

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