Show off your Python chops and compete with others

[Nathaniel Sokoll-Ward]

Thought this group would appreciate this: www.metabright.com/challenges/python

MetaBright makes skill assessments to measure how talented people are at different skills. And recruiters use MetaBright to find outrageously skilled job candidates.

Python is a new area of expertise for us. We make "Challenges" for a bunch of languages and we're excited to finally have Python released. Give it a shot -- I'd love to hear what you think.

[Andrew Cooper]

"What is the correct number of spaces for indentation in Python?"

I presume the question should be more along the lines of "What does PEP8
say?", because all answers are correct.

"String literals are written with what?"

The answer is not "ALl of these answers are correct"


So two of of 7 questions with wrong answers so far...

~Andrew

[Roy Smith]

In article <jWAeu.102858$rN3....@fx21.am4>,

Andrew Cooper <ro...@127.0.0.1> wrote:

> On 07/11/2013 00:00, Nathaniel Sokoll-Ward wrote:
> > Thought this group would appreciate this:
> > www.metabright.com/challenges/python
> >
> > MetaBright makes skill assessments to measure how talented people are at
> > different skills. And recruiters use MetaBright to find outrageously
> > skilled job candidates.
> >
> > Python is a new area of expertise for us. We make "Challenges" for a bunch
> > of languages and we're excited to finally have Python released. Give it a
> > shot -- I'd love to hear what you think.
> >
>
> "What is the correct number of spaces for indentation in Python?"

What does the following code do?
def a(b, c, d): pass

My answer: "Defines a function which returns None", but that isn't one
of the choices.

[Andrew Cooper]

"Which is a correct way to perform exponentiation in Python?"

1) math.pow(a,b)
2) a^b
3) a*2b
4) None of the other responses are correct

Apparently I was wrong by answering 4), and 1) is the expected answer.
Clearly the author doesn't know about the ** operator in python.


It appears that no serious python coders were consulted when writing
these questions.

~Andrew

[Mark Lawrence]

So that narrows the search for the culprit down to our Greek aquaintance? :)

--
Python is the second best programming language in the world.
But the best has yet to be invented. Christian Tismer

Mark Lawrence

[Chris Angelico]

"""How could you open a file c:\scores.dat to write in binary?

outfile = open("c:\\scores.dat", "w")
outfile = open("c:\scores.dat", "a")
outfile = open("c:\\scores.dat", "w")
outfile = open("c:\\scores.dat", "wb")"""

Not technically wrong, but stylistically suspect; I would recommend
using forward slashes (which work fine on Windows) and avoiding the
drive letter, both of which avoid making your example
Windows-specific. (At least, I don't think there are any other
platforms Python supports that use drive letters; OS/2 support was
dropped a little while ago, though I believe Paul Smedley still
maintains a port. But I digress.)

"""Which method will write a pickled representation of the object to
an open file?"""

Method names without object names aren't all that useful. Do you mean
"Which method of the pickle module..."?

"""From which languages are Python classes derived from?"""

Sounds like Python history trivia more than a coding challenge, but if
that's what you want to go for, sure.

ChrisA

[Chris Angelico]

On Thu, Nov 7, 2013 at 11:00 AM, Nathaniel Sokoll-Ward
<nathaniel...@gmail.com> wrote:

By the way, here's a fairly bad solution to your final question:

array666=lambda x:b"\6\6\6" in bytes(x)

Works for the given test-cases! Doesn't work with arrays at all,
despite the description.

ChrisA

[MRAB]

On 07/11/2013 00:59, Chris Angelico wrote:
> On Thu, Nov 7, 2013 at 11:00 AM, Nathaniel Sokoll-Ward
> <nathaniel...@gmail.com> wrote:

> """How could you open a file c:\scores.dat to write in binary?
>
> outfile = open("c:\\scores.dat", "w")
> outfile = open("c:\scores.dat", "a")
> outfile = open("c:\\scores.dat", "w")
> outfile = open("c:\\scores.dat", "wb")"""
>
> Not technically wrong, but stylistically suspect; I would recommend
> using forward slashes (which work fine on Windows) and avoiding the
> drive letter, both of which avoid making your example
> Windows-specific. (At least, I don't think there are any other
> platforms Python supports that use drive letters; OS/2 support was
> dropped a little while ago, though I believe Paul Smedley still
> maintains a port. But I digress.)
>
> """Which method will write a pickled representation of the object to
> an open file?"""
>
> Method names without object names aren't all that useful. Do you mean
> "Which method of the pickle module..."?
>
> """From which languages are Python classes derived from?"""
>

Does it really have the word "from" twice?

[Chris Angelico]

On Thu, Nov 7, 2013 at 12:12 PM, MRAB <pyt...@mrabarnett.plus.com> wrote:
>> """From which languages are Python classes derived from?"""
>>
> Does it really have the word "from" twice?

You know, I didn't even notice that. But since that was copied and
pasted, I would say that yes, it really does. That's a pretty simple
grammatical bugfix though.

ChrisA

[John Nagle]

On 11/6/2013 5:04 PM, Chris Angelico wrote:
> On Thu, Nov 7, 2013 at 11:00 AM, Nathaniel Sokoll-Ward
> <nathaniel...@gmail.com> wrote:
>> Thought this group would appreciate this: www.metabright.com/challenges/python
>>
>> MetaBright makes skill assessments to measure how talented people are at different skills. And recruiters use MetaBright to find outrageously skilled job candidates.

With tracking cookies blocked, you get 0 points.

John Nagle

[John Ladasky]

On Wednesday, November 6, 2013 4:00:57 PM UTC-8, Nathaniel Sokoll-Ward wrote:
> Thought this group would appreciate this: www.metabright.com/challenges/python

I have to concur with what several other people are saying here. Several of MetaBright's questions are ambiguously worded, or expect non-idiomatic Python code. It might be helpful for you to ask (hire?) some seasoned Python programmers to critique your questions.

[Chris Angelico]

No need to hire anyone, just posting the questions here will generate
exactly such a critique - as evidenced by this thread :)

ChrisA

[Tim Chase]

On 2013-11-06 17:31, John Nagle wrote:
> >> MetaBright makes skill assessments to measure how talented
> >> people are at different skills. And recruiters use MetaBright to
> >> find outrageously skilled job candidates.
>
> With tracking cookies blocked, you get 0 points.

And with JavaScript blocked, you get bupkis. :-)

I was amused that the sidebar of similar challenges suggested that
the Python challenge might be similar to this one. Ya think? So
similar that even the URL is the same...

-tkc

[Nathaniel Sokoll-Ward]

Wow! Thanks for all the feedback everyone. This content is fresh so I appreciate everyone's comments. As opposed to responding to each post individually, I'll just lump everything in here...

Andrew, big thanks for your comments:

> "What is the correct number of spaces for indentation in Python?"
>

> I presume the question should be more along the lines of "What does PEP8
> say?", because all answers are correct.

I agree. Question has been edited.

>
> "String literals are written with what?"
>
> The answer is not "ALl of these answers are correct"

I believe that string literals can be written with single, double, or triple quotes: http://docs.python.org/release/2.5.2/ref/strings.html

> "Which is a correct way to perform exponentiation in Python?"

This was a silly error. Thanks for pointing it out.

> What does the following code do?
> def a(b, c, d): pass
>
> My answer: "Defines a function which returns None", but that isn't one
> of the choices.

Roy, thanks for your note. When I run this code, the function just gets defined and nothing happens. None isn't returned. Do you recall why you found the options available to you unsuitable?

> """How could you open a file c:\scores.dat to write in binary?
>
> outfile = open("c:\\scores.dat", "w")
> outfile = open("c:\scores.dat", "a")
> outfile = open("c:\\scores.dat", "w")
> outfile = open("c:\\scores.dat", "wb")"""
>
> Not technically wrong, but stylistically suspect; I would recommend
> using forward slashes (which work fine on Windows) and avoiding the
> drive letter, both of which avoid making your example
> Windows-specific. (At least, I don't think there are any other
> platforms Python supports that use drive letters; OS/2 support was
> dropped a little while ago, though I believe Paul Smedley still
> maintains a port. But I digress.)

Excellent suggestion. We've gone ahead and made the change.

>
> """Which method will write a pickled representation of the object to
> an open file?"""
>
> Method names without object names aren't all that useful. Do you mean
> "Which method of the pickle module..."?

Again, great suggestion.

>
> """From which languages are Python classes derived from?"""
>

> Sounds like Python history trivia more than a coding challenge, but if
> that's what you want to go for, sure.

I agree it's not directly coding related. Our questions are actually sorted into topic buckets. We try to get a reading on people's knowledge in a bunch of different areas of a given skill. Familiarity with general knowledge facts such as this, gives us another data point to help parse out the types of questions the best developers tend to get right.

> By the way, here's a fairly bad solution to your final question:
>
> array666=lambda x:b"\6\6\6" in bytes(x)
>
> Works for the given test-cases! Doesn't work with arrays at all,
> despite the description.

Chris, I actually really like your answer, even if it doesn't satisfy the goal in the question. I'd give it a vote for cleverness!

> You know, I didn't even notice that. But since that was copied and
> pasted, I would say that yes, it really does. That's a pretty simple
> grammatical bugfix though.

Silly error. Fixed.

> I have to concur with what several other people are saying here. Several of MetaBright's questions are > ambiguously worded, or expect non-idiomatic Python code. It might be helpful for you to ask (hire?) > some seasoned Python programmers to critique your questions.

Thanks for the thoughts, John. I'd be lying if I said I wasn't disappointed with how many errors everyone here is picking out. Some of our Challenges are built exclusively by our users, others are built by someone who helped build MetaBright, while others, like the Python Challenge, are built with the help of contractors. Even so, the responsibility to make sure we are publishing high quality content falls on our shoulders and I regret we didn't go a better job of vetting this material.

> With tracking cookies blocked, you get 0 points.

> And with JavaScript blocked, you get bupkis. :-)

I know that's frustrating. Our tech lead will be on here later today to explain why we do this.

Thanks again everyone!

[Mark Lawrence]

On 07/11/2013 18:38, Nathaniel Sokoll-Ward wrote:
>>
>> My answer: "Defines a function which returns None", but that isn't one
>> of the choices.
>
> Roy, thanks for your note. When I run this code, the function just gets defined and nothing happens. None isn't returned. Do you recall why you found the options available to you unsuitable?
>

>>> def a(b, c, d): pass

...
>>> x=a(1,2,3);type(x)
<class 'NoneType'>

[jsk...@gmail.com]

We do not currently support cookieless or javascript-less browsing. We are definitely looking at relying less and less on cookies, but it's unlikely we'll ever be able to pull out javascript as it limits interactivity too much. Its definitely possible to do, and maybe something we can look at in the future, but right now we don't have the resources for that. Sorry for the inconvenience!

- Jonathan Kirst
Lead Engineer at MetaBright

[Alister]

On Thu, 07 Nov 2013 10:38:40 -0800, Nathaniel Sokoll-Ward wrote:

> Wow! Thanks for all the feedback everyone. This content is fresh so I
> appreciate everyone's comments. As opposed to responding to each post
> individually, I'll just lump everything in here...
>
>
>>

>> My answer: "Defines a function which returns None", but that isn't one
>> of the choices.
>
> Roy, thanks for your note. When I run this code, the function just gets
> defined and nothing happens. None isn't returned. Do you recall why you
> found the options available to you unsuitable?

your sites answer is " defines a function that does nothing"
once you have defined the function try print (a(1,2,3))
you will see that is does indeed return none, as do all functions without
an explicit return.
>

> Thanks again everyone!
--
While you recently had your problems on the run, they've regrouped and
are making another attack.

[Tim Chase]

On 2013-11-07 11:02, jsk...@gmail.com wrote:
> it's unlikely we'll ever be able to pull out javascript as it
> limits interactivity too much.

It was mostly in jest as it's one of the things I test when doing
web development. That said, the quizzes are mostly just HTML forms
where you pick the answer with a radio button and click the [next]
button. There's not much interactivity there that hasn't been around
since the dawn of the web.

Additionally, I noticed that if I accidentally select an answer
(laptop track-pads aren't the most precise pointing devices), there
was no readily-apparent way to change/fix it before hitting [next].

-tkc

[Chris Angelico]

On Fri, Nov 8, 2013 at 5:38 AM, Nathaniel Sokoll-Ward
<nathaniel...@gmail.com> wrote:
> Wow! Thanks for all the feedback everyone. This content is fresh so I appreciate everyone's comments. As opposed to responding to each post individually, I'll just lump everything in here...

Best way, I think :)

> I believe that string literals can be written with single, double, or triple quotes: http://docs.python.org/release/2.5.2/ref/strings.html

Hmm. As a general rule, can you consider aiming your quiz - and any
citations like this - at a current version of Python? I'd prefer to
see this sort of thing aimed at the 3.3 docs, though if you want to
cite 2.7 that would also be of value. But 2.5 is now quite old, and
I'd rather not get the impression that you're writing a quiz based on
an unsupported version of Python. :) Though in this particular
instance it makes no difference.

>> By the way, here's a fairly bad solution to your final question:
>>
>> array666=lambda x:b"\6\6\6" in bytes(x)
>>
>> Works for the given test-cases! Doesn't work with arrays at all,
>> despite the description.
>
> Chris, I actually really like your answer, even if it doesn't satisfy the goal in the question. I'd give it a vote for cleverness!

Heh. Do you know what the limitation of my solution is, though? As I
said, it works for the given test-cases; what sort of input will it
fail on? (And also: What's its algorithmic complexity, and what's the
complexity of a better solution?) That's why I said it's a bad
solution :)

The side comment about arrays, though: Python *does* have arrays, but
they're a different beast from what you're working with, which are
called lists. The version I posted will actually work with any
iterable, but specifying that it be a list might open up some other
options.

BTW, you're going to see a lot of criticism on the list, because
that's the natural state of things. Doesn't mean we didn't enjoy
taking the quiz. :)

In your Intermediate section:
"""Which of the following is false regarding the raw_input() and
input() built-in functions in Python?

The old raw_input() has been renamed to input() in Python 3.x
input() is equivalent to exec(raw_input())
In Python 2.x, raw_input() returns a string.
raw_input() does not exist in Python 3.x"""

Technically one of those is false, but (a) you really need to specify
versions a LOT more clearly here, and (b) the falseness is a minor
technicality; it took me a while to notice that you'd written exec
where it actually uses eval. Is that distinction really worth
highlighting in the quiz?

"""Which of the following statements is false?

Python can be used to generate dynamic web pages.
Python can be used for web development.
Python's syntax is much like PHP.
Python can run on any type of platform."""

What does *any type* of platform mean? Do you mean "any platform", and
if so, do you mean that there is no pocket calculator on which Python
doesn't run? Or is there some other "type" of platform?

>>> type(platform)
<class 'module'>

I get it. Python will run on any module. *dives for cover*

BTW, here's my chosen "bad solution" for the boss question at the end
of the intermediate section. I'm sure someone here can come up with a
worse one. Wasn't sure what should be done if all three numbers are
the same, incidentally.

def indie_three(*numbers):
seen = {}
tot = 0
for n in numbers:
seen.setdefault(n, 5)
seen[n] -= 4
tot += n * seen[n]
return tot

Note how I've generalized it to any number of input values AND to any
possible number of duplicates!

ChrisA

[88888 Dihedral]

That is easy. Please use FireFox
plus NoScript to achieve what you
want.

[Roy Smith]

In article <pyReu.25286$ql7....@fx33.am4>,

Alister <aliste...@ntlworld.com> wrote:

> your sites answer is " defines a function that does nothing"
> once you have defined the function try print (a(1,2,3))
> you will see that is does indeed return none, as do all functions without
> an explicit return.

Well, if you want to be truly pedantic about it (*), this defines a
function without an explicit return and which does not return None:

def foo():
raise Exception

and, for that matter:

def bar():
import os
os._exit(0) # Or variations, such as exec()

(*) and I do.

[alex23]

On 8/11/2013 11:02 AM, Roy Smith wrote:
> Well, if you want to be truly pedantic about it (*), this defines a
> function without an explicit return and which does not return None:
>
> def foo():
> raise Exception

In [2]: import dis
In [3]: dis.dis(foo)
2 0 LOAD_GLOBAL 0 (Exception)
3 RAISE_VARARGS 1
6 LOAD_CONST 0 (None)
9 RETURN_VALUE

Seeing as we're being pedantic, the function *does* return None, it's
just that the return value is never seen because an exception is raise.

[Roy Smith]

In article <l5hfuj$m2n$1...@dont-email.me>, alex23 <wuw...@gmail.com>
wrote:

Dead code doesn't count.

[alex23]

On 8/11/2013 11:54 AM, Roy Smith wrote:
> Dead code doesn't count.

Neither do shifting goalposts.

[Roy Smith]

In article <l5hh32$qf4$1...@dont-email.me>, alex23 <wuw...@gmail.com>
wrote:

> On 8/11/2013 11:54 AM, Roy Smith wrote:
> > Dead code doesn't count.
>
> Neither do shifting goalposts.

It's not a shifting goalpost. My original statement was that:

def foo():
raise Exception

defines a function which 1) has no explicit return statement and 2) does
not return None. I stand by that statement. There is no possible
codepath, no possible calling sequence, no possible execution
environment, which will cause that function to return None. That fact
that one particular Python implementation happens to produce unreachable
bytecode for returning None is meaningless. Would you say that:

def baz():
return None
print "I got here"

is a function which prints "I got here"?

[Chris Angelico]

On Fri, Nov 8, 2013 at 1:18 PM, Roy Smith <r...@panix.com> wrote:
> It's not a shifting goalpost. My original statement was that:
>
> def foo():
> raise Exception
>
> defines a function which 1) has no explicit return statement and 2) does
> not return None. I stand by that statement. There is no possible
> codepath, no possible calling sequence, no possible execution
> environment, which will cause that function to return None. That fact
> that one particular Python implementation happens to produce unreachable
> bytecode for returning None is meaningless. Would you say that:
>
> def baz():
> return None
> print "I got here"
>
> is a function which prints "I got here"?

Granted, but I would describe this:

def foo(x):
return "Hello, world!\n" + str(x)

as a function which returns a string. Is it? Well, not if str raises
an exception. Even if the only arguments you can give to foo will
result in exceptions, I would still say that, per design, this is a
function that returns a string. The possibility of raising an
exception (and thus not returning anything) doesn't change a
function's return type (by which I mean more than just what C would
use as the declaration - I could just as well say "Returns the name of
an employee", and the same argument would apply).

ChrisA

[Tim Chase]

On 2013-11-07 21:18, Roy Smith wrote:
> It's not a shifting goalpost. My original statement was that:
>
> def foo():
> raise Exception
>
> defines a function which 1) has no explicit return statement and 2)
> does not return None. I stand by that statement. There is no
> possible codepath, no possible calling sequence, no possible
> execution environment, which will cause that function to return
> None.

Well, for varying definitions of "that function", you can do

>>> def unerr(fn):
... def wrapper(*args, **kwargs):
... try:
... fn(*args, **kwargs)
... except:
... return None
... return wrapper
...
>>> @unerr
... def foo():
... raise Exception
...
>>> print foo()
None

;-)

Beyond that, I'm sure one could resort to bytecode hacking to have
"that function" skip the raise...

-tkc

[Steven D'Aprano]

On Thu, 07 Nov 2013 22:05:14 -0600, Tim Chase wrote:

> On 2013-11-07 21:18, Roy Smith wrote:
>> It's not a shifting goalpost. My original statement was that:
>>
>> def foo():
>> raise Exception
>>
>> defines a function which 1) has no explicit return statement and 2)
>> does not return None. I stand by that statement. There is no possible
>> codepath, no possible calling sequence, no possible execution
>> environment, which will cause that function to return None.
>
> Well, for varying definitions of "that function", you can do

[snip modified functions]

> Beyond that, I'm sure one could resort to bytecode hacking to have "that
> function" skip the raise...

Now who's shifting the goalposts? Whether you edit the function's source
code, wrap it in a decorator, or hack it's byte-code, it's not the same
function as the one Roy showed above by any reasonable definition of "the
same". As an intellectual exercise of how one might subvert the standard
semantics of the Python compiler, it is interesting to consider (say)
byte-code hacks that turn this source code:

def foo():
raise Exception

into something that returns None, but by the same logic one might say
that this function:

def spam():
return 42

connects to some database over the Internet and deletes any table
containing more than seven records. If we're going to allow those sorts
of debating shenanigans, the obvious counter is "yes, but when I said
that the function doesn't return None, I actually meant that it doesn't
solve the Halting Problem, and it still doesn't do that, so I win nyah
nyah nyah".



--
Steven

[Gregory Ewing]

alex23 wrote:
> In [2]: import dis
> In [3]: dis.dis(foo)
> 2 0 LOAD_GLOBAL 0 (Exception)
> 3 RAISE_VARARGS 1
> 6 LOAD_CONST 0 (None)
> 9 RETURN_VALUE
>
> Seeing as we're being pedantic, the function *does* return None, it's
> just that the return value is never seen because an exception is raise.

Koan for the day:

If a man goes into the forest and never returns,
does he bring back nothing?

--
Greg

[Omar Abou Mrad]

On Thu, Nov 7, 2013 at 2:00 AM, Nathaniel Sokoll-Ward <nathaniel...@gmail.com> wrote:

Thought this group would appreciate this: www.metabright.com/challenges/python

MetaBright makes skill assessments to measure how talented people are at different skills. And recruiters use MetaBright to find outrageously skilled job candidates.

Python is a new area of expertise for us. We make "Challenges" for a bunch of languages and we're excited to finally have Python released. Give it a shot -- I'd love to hear what you think.

--
https://mail.python.org/mailman/listinfo/python-list

Nathaniel,

You may want to classify the questions under some weight. You can't really have a level 6 question about semi colon.

Also, when the boss questions are being computed, you should run more than the 'example' given as a test, otherwise users can just cheat. For example, I think one of the 'Boss' question was return the first 3 digits of PI as a list, all i did was:

return [3,1,4]

Hope this helps.

[Mark Lawrence]

Game, set and match to Roy Smith? :)

[Nathaniel Sokoll-Ward]

Hi Omar,

Thanks for the suggestions! 

Your point about question difficulty is well taken. We previously organized questions into sections based on difficulty or topic, but have been experimenting with doing away with sections entirely. We are developing a way to intelligently deliver questions to a user based on their perceived skill level.

You're right that our checks can be defeated with sneakiness, but in the end we believe that it makes more sense to implement incentives to encourage people to post high quality answers, than to build full-proof validation tools.

Thanks again!