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PyWart: Itertools module needs attention

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  PyWart: Itertools module needs attention rantingrick <rantingrick@gmail.com> - 2011-09-12 15:04 -0700
    Re: PyWart: Itertools module needs attention Ethan Furman <ethan@stoneleaf.us> - 2011-09-12 16:29 -0700
    Re: PyWart: Itertools module needs attention Ian Kelly <ian.g.kelly@gmail.com> - 2011-09-13 09:45 -0600
      Re: PyWart: Itertools module needs attention rantingrick <rantingrick@gmail.com> - 2011-09-13 19:08 -0700

#13202 — PyWart: Itertools module needs attention

############################################################
#                          Quote                           #
############################################################
# The itertools module is great HOWEVER i believe most     #
# people are recreating the functionalities due to the     #
# insanely cryptic and/or missing examples from each       #
# method                                                   #
############################################################

py> print itertools.chain.__doc__
chain(*iterables) --> chain object
Return a chain object whose .next() method returns elements from the
first iterable until it is exhausted, then elements from the next
iterable, until all of the iterables are exhausted.

############################################################
#                          Quote                           #
############################################################
# Okay not TOO bad however this simple example would       #
# suffice:                                                 #
############################################################

py> list(itertools.chain([1,2], [3,[4,5],6]))
[1, 2, 3, [4, 5], 6]

############################################################
#                          Quote                           #
############################################################
# Same for these...                                        #
############################################################

py> ''.join(list(itertools.dropwhile(lambda x:x==" ", "    hello
word    ")))
'hello word    '
py> ''.join(list(itertools.takewhile(lambda x:x==" ", "    hello
word    ")))
'    '
py> print itertools.compress.__doc__
compress(data, selectors) --> iterator over selected data
Return data elements corresponding to true selector elements.
Forms a shorter iterator from selected data elements using the
selectors to choose the data elements.

############################################################
#                          Quote                           #
############################################################
# WTF! Would you like to define a Python "selector". Could #
# it be that we should be using "selector function" or     #
# "predicate function" instead?                            #
############################################################

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#13204

Nick Stinemates wrote:
> I'm honestly missing the point of this mail.


rantingrick is a well-known troll, and doesn't need to have a point.

Please do not feed the troll.

~Ethan~

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#13236

On Mon, Sep 12, 2011 at 4:04 PM, rantingrick <rantingrick@gmail.com> wrote:
>
> ############################################################
> #                          Quote                           #
> ############################################################
> # The itertools module is great HOWEVER i believe most     #
> # people are recreating the functionalities due to the     #
> # insanely cryptic and/or missing examples from each       #
> # method                                                   #
> ############################################################

Have you looked at the online itertools documentation at all?

http://docs.python.org/library/itertools.html

> py> ''.join(list(itertools.dropwhile(lambda x:x==" ", "    hello
> word    ")))
> 'hello word    '
> py> ''.join(list(itertools.takewhile(lambda x:x==" ", "    hello
> word    ")))
> '    '

These are too complex to be good examples.  Drop the lambda and
replace it with a built-in.  Also, str.join is perfectly capable of
taking an iterator as its argument.  There is no reason at all to
construct a list first.

> py> print itertools.compress.__doc__
> compress(data, selectors) --> iterator over selected data
> Return data elements corresponding to true selector elements.
> Forms a shorter iterator from selected data elements using the
> selectors to choose the data elements.
>
> ############################################################
> #                          Quote                           #
> ############################################################
> # WTF! Would you like to define a Python "selector". Could #
> # it be that we should be using "selector function" or     #
> # "predicate function" instead?                            #
> ############################################################

Notice that it says "selector elements", not "selector functions".
You have misconstrued what this function does.  Hint: it does not use
predicates at all.

I can agree though that this could probably use a simple example in
the doc string.

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#13256

On Sep 13, 10:45 am, Ian Kelly <ian.g.ke...@gmail.com> wrote:

> Have you looked at the online itertools documentation at all?
>
> http://docs.python.org/library/itertools.html

Yes the online docs are much better. I really like the source code
showing the inner workings of the methods. However i always get upset
when i see poorly thought out doc-strings. My philosophy is that we
should use the built in help function first and only visit the
documentation if more instruction is needed.


I may need to create another PyWart on the topic of doc-strings and
how the author of these strings needs to forget everything he knows
and imagine he is a complete python neophyte. I remember my initial
frustrations learning about functions (in another life it seems) and
my inability to grasp the concept was due to poor examples. I believe
the author use the Fibonacci sequence as an example (Python docs use
this example also). What an idiot!

What does conditionals, linear assignment, loops, the print function,
in-place addition, logic, blah, blah, have to do with understanding a
function... NOTHING! The most basic and by far the best first example
for functions (in any language) is this...

def add(x, y):
    return x + y

Followed by this...

def sub(x,y):
    return x - y

Simple and to the point. It simply reeks of "ah ha"! I dare anyone to
create a better introductory function example. Dear Tutorial Writer:
When writing tutorials please check your ego at the door. Thank you.

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