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Most probably a stupid question, but I still want to ask

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  Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 18:51 -0400
    Re: Most probably a stupid question, but I still want to ask Chris Angelico <rosuav@gmail.com> - 2016-04-11 08:58 +1000
    Re: Most probably a stupid question, but I still want to ask Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 09:04 +1000
    Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 16:30 -0700
      Re: Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:17 -0400
        Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:32 -0700
        Re: Most probably a stupid question, but I still want to ask Terry Reedy <tjreedy@udel.edu> - 2016-04-10 21:45 -0400
          Re: Most probably a stupid question, but I still want to ask Marko Rauhamaa <marko@pacujo.net> - 2016-04-11 08:41 +0300
    one-element tuples [Was: Most probably a stupid question, but I still want to ask] Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:13 -0400
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:19 -0700
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:18 -0700
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Chris Angelico <rosuav@gmail.com> - 2016-04-11 10:20 +1000
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:22 -0400
        Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:28 -0700
        Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:31 +1000
          Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:48 -0400
            Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:56 +1000
              Re: one-element tuples Grant Edwards <invalid@invalid.invalid> - 2016-04-11 14:10 +0000
                Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-11 10:11 -0400
                  Re: one-element tuples Grant Edwards <invalid@invalid.invalid> - 2016-04-11 14:26 +0000
            Re: one-element tuples Ned Batchelder <ned@nedbatchelder.com> - 2016-04-10 18:00 -0700
            Re: one-element tuples Stephen Hansen <me+python@ixokai.io> - 2016-04-10 18:07 -0700
            Re: one-element tuples "Martin A. Brown" <martin@linux-ip.net> - 2016-04-10 18:08 -0700
              Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 23:19 -0400
                Re: one-element tuples Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-04-11 09:57 +0300
                Re: one-element tuples Larry Hudson <orgnut@yahoo.com> - 2016-04-11 23:01 -0700
            Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 11:36 +1000
              Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 22:57 -0400
                Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 14:10 +1000
                  Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-11 00:43 -0400
                    Re: one-element tuples Stephen Hansen <me+python@ixokai.io> - 2016-04-10 21:54 -0700
                    Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 15:40 +1000
                  Re: one-element tuples Rustom Mody <rustompmody@gmail.com> - 2016-04-10 22:07 -0700
            Re: one-element tuples BartC <bc@freeuk.com> - 2016-04-11 12:15 +0100
              Re: one-element tuples Marko Rauhamaa <marko@pacujo.net> - 2016-04-11 15:12 +0300
                Re: one-element tuples Grant Edwards <invalid@invalid.invalid> - 2016-04-11 14:12 +0000
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:30 +1000
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] MRAB <python@mrabarnett.plus.com> - 2016-04-11 01:33 +0100
        Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Dan Sommers <dan@tombstonezero.net> - 2016-04-11 02:22 +0000
          Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Chris Angelico <rosuav@gmail.com> - 2016-04-11 12:34 +1000
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Chris Angelico <rosuav@gmail.com> - 2016-04-11 10:38 +1000
      Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:45 +1000
      Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Chris Angelico <rosuav@gmail.com> - 2016-04-11 10:50 +1000
      Re: Parens do create a tuple Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:57 +1000
      Re: Parens do create a tuple Chris Angelico <rosuav@gmail.com> - 2016-04-11 11:04 +1000
      Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Stephen Hansen <me@ixokai.io> - 2016-04-10 18:03 -0700
      Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Tim Chase <python.list@tim.thechases.com> - 2016-04-10 19:52 -0500
      Re: Parens do create a tuple Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 11:41 +1000
        Re: Parens do create a tuple Steven D'Aprano <steve@pearwood.info> - 2016-04-11 12:32 +1000
          Re: Parens do create a tuple Random832 <random832@fastmail.com> - 2016-04-10 22:51 -0400
            Re: Parens do create a tuple Steven D'Aprano <steve@pearwood.info> - 2016-04-11 14:08 +1000
              Re: Parens do create a tuple Random832 <random832@fastmail.com> - 2016-04-11 01:27 -0400
                Re: Parens do create a tuple Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-04-11 18:01 +1000
                  Re: Parens do create a tuple Random832 <random832@fastmail.com> - 2016-04-11 09:42 -0400
          Re: Parens do create a tuple Chris Angelico <rosuav@gmail.com> - 2016-04-11 13:02 +1000
          Re: Parens do create a tuple Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 14:08 +1000
      Re: Parens do create a tuple Chris Angelico <rosuav@gmail.com> - 2016-04-11 11:51 +1000
        Re: Parens do create a tuple Steven D'Aprano <steve@pearwood.info> - 2016-04-11 12:57 +1000
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Tim Chase <python.list@tim.thechases.com> - 2016-04-10 19:46 -0500
    Re: Most probably a stupid question, but I still want to ask Steven D'Aprano <steve@pearwood.info> - 2016-04-11 11:50 +1000
      Re: Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 22:48 -0400
        Re: Most probably a stupid question, but I still want to ask Steven D'Aprano <steve@pearwood.info> - 2016-04-11 13:54 +1000
          Re: Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-11 00:03 -0400
            Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 21:46 -0700
              Re: Most probably a stupid question, but I still want to ask Rustom Mody <rustompmody@gmail.com> - 2016-04-10 22:18 -0700
                Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 22:42 -0700
                  Re: Most probably a stupid question, but I still want to ask Rustom Mody <rustompmody@gmail.com> - 2016-04-10 23:57 -0700
            Re: Most probably a stupid question, but I still want to ask Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-04-11 17:50 +1000

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#106799 — Most probably a stupid question, but I still want to ask

let's look at this:

$ python3.4
Python 3.4.0 (default, Apr 11 2014, 13:05:11)
[GCC 4.8.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
 >>> line1 = '"String1" | bla'
 >>> parts1 = line1.split(" | ")
 >>> parts1
['"String1"', 'bla']
 >>> tokens1 = eval(parts1[0])
 >>> tokens1
'String1'
 >>> tokens1[0]
'S'

and now this

 >>> line2 = '"String1","String2" | bla'
 >>> parts2 = line2.split(" | ")
 >>> tokens2 = eval(parts2[0])
 >>> tokens2
('String1', 'String2')
 >>> tokens2[0]
'String1'
 >>> type(tokens1)
<class 'str'>
 >>> type(tokens2)
<class 'tuple'>
 >>>


the question is: at which point did the language designers decide to betray the
"path of least surprise" principle and create a 'discontinuity' in the language?
Open to the idea that I am getting something fundamentally wrong. I'm new to Python...

Thanks

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#106800

On Mon, Apr 11, 2016 at 8:51 AM, Fillmore <fillmore_remove@hotmail.com> wrote:
> the question is: at which point did the language designers decide to betray
> the
> "path of least surprise" principle and create a 'discontinuity' in the
> language?
> Open to the idea that I am getting something fundamentally wrong. I'm new to
> Python...

Can you please simplify your example and show what the discontinuity
is you're referring to? You keep messing with eval and split and
stuff, and then looking at the types of things. Which part are you
surprised at?

ChrisA

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#106801

Fillmore <fillmore_remove@hotmail.com> writes:

> let's look at this:

Can you set a “Subject” field that pertains to the actual question? As
is, it doesn't help know what you want to discuss.

> the question is: at which point did the language designers decide to
> betray the "path of least surprise" principle and create a
> 'discontinuity' in the language?

This, also, doesn't help us know what the question is.

Please describe what you expect that code to do, and if possible what it
is that surprises you about its behaviour.

-- 
 \       “Repetition leads to boredom, boredom to horrifying mistakes, |
  `\       horrifying mistakes to God-I-wish-I-was-still-bored, and it |
_o__)              goes downhill from there.” —Will Larson, 2008-11-04 |
Ben Finney

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#106802

On Sun, Apr 10, 2016, at 03:51 PM, Fillmore wrote:
> 
> let's look at this:
> 
> $ python3.4
> Python 3.4.0 (default, Apr 11 2014, 13:05:11)
> [GCC 4.8.2] on linux
> Type "help", "copyright", "credits" or "license" for more information.
>  >>> line1 = '"String1" | bla'
>  >>> parts1 = line1.split(" | ")
>  >>> parts1
> ['"String1"', 'bla']
>  >>> tokens1 = eval(parts1[0])
>  >>> tokens1
> 'String1'
>  >>> tokens1[0]
> 'S'
> 
> and now this
> 
>  >>> line2 = '"String1","String2" | bla'
>  >>> parts2 = line2.split(" | ")
>  >>> tokens2 = eval(parts2[0])

I *THINK* what you're asking is why this returns a tuple, where in the
first eval you got a string. The answer is because commas create tuples
(not parens), so:

    "String1", "String2"

is a tuple expression. Whereas:

    "String1"

is a string expression. 

> the question is: at which point did the language designers decide to
> betray the
> "path of least surprise" principle and create a 'discontinuity' in the
> language?

There's nothing inconsistent or surprising going on besides you doing
something vaguely weird and not really expressing what you find
surprising.

--Stephen
m e @ i x o k a i . i o

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#106804

On 04/10/2016 07:30 PM, Stephen Hansen wrote:

> There's nothing inconsistent or surprising going on besides you doing
> something vaguely weird and not really expressing what you find
> surprising.

well, I was getting some surprising results for some of my data, so I can
guarantee that I was surprised!

apparently my 'discontinuity' is mappable to the fact that there's no such
thing as one-element tuples in Python, and attempts to create one will
result in a string (i.e. an object of a different kind!)...

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#106811

On Sun, Apr 10, 2016, at 05:17 PM, Fillmore wrote:
> On 04/10/2016 07:30 PM, Stephen Hansen wrote:
> 
> > There's nothing inconsistent or surprising going on besides you doing
> > something vaguely weird and not really expressing what you find
> > surprising.
> 
> well, I was getting some surprising results for some of my data, so I can
> guarantee that I was surprised!

The point is you are not saying *what* is surprising. Nothing in your
example code looks the least bit surprising to me, but I've been using
Python for ages. If you're surprised by something, say *what* surprises
you at the very least.

But to repeat what I said that you didn't quote: the thing you need to
understand is that parentheses do not create tuples, commas do.

Parentheses only group things together.

--Stephen
m e @ i x o k a i . i o

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#106831

On 4/10/2016 8:17 PM, Fillmore wrote:

> apparently my 'discontinuity' is mappable to the fact that there's no such
> thing as one-element tuples in Python, and attempts to create one will
> result in a string (i.e. an object of a different kind!)...

Please work through the tutorial before posting wrong information
about the basics of Python.

 >>> t = 1,
 >>> t
(1,)

-- 
Terry Jan Reedy

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#106860

Terry Reedy <tjreedy@udel.edu>:

> On 4/10/2016 8:17 PM, Fillmore wrote:
>
>> apparently my 'discontinuity' is mappable to the fact that there's no
>> such thing as one-element tuples in Python, and attempts to create
>> one will result in a string (i.e. an object of a different kind!)...
>
> Please work through the tutorial before posting wrong information
> about the basics of Python.
>
>>>> t = 1,
>>>> t
> (1,)

However, in some languages, one-dimensional vectors/tuples and scalars
are treated as equivalent (at least APL and Scheme).


Marko

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#106803 — one-element tuples [Was: Most probably a stupid question, but I still want to ask]

Sorry guys. It was not my intention to piss off anyone...just trying to understand how the languare works

I guess that the answer to my question is: there is no such thing as a one-element tuple,
and Python will automatically convert a one-element tuple to a string... hence the
behavior I observed is explained...

 >>> a = ('hello','bonjour')
 >>> b = ('hello')
 >>> b
'hello'
 >>> a
('hello', 'bonjour')
 >>>


Did I get this right this time?

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#106805 — Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]

On Sun, Apr 10, 2016, at 05:18 PM, Stephen Hansen wrote:
> The parens are optional, I always put them in because:
> >>> b = "hello",

Ahem, "because its easy to miss the trailing comma" is what I meant to
say here.

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#106806 — Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]

On Sun, Apr 10, 2016, at 05:13 PM, Fillmore wrote:
> I guess that the answer to my question is: there is no such thing as a
> one-element tuple,
> and Python will automatically convert a one-element tuple to a string...
> hence the
> behavior I observed is explained...
> 
>  >>> a = ('hello','bonjour')
>  >>> b = ('hello')
>  >>> b
> 'hello'
>  >>> a
> ('hello', 'bonjour')
>  >>>
> 
> 
> Did I get this right this time?

No, you didn't. Your mistake is again -- parens don't make tuples,
commas do.

A one element tuple is:
>>> b = ("hello,)

The parens are optional, I always put them in because:
>>> b = "hello",

The parens group an expression, they don't make a type.

--
Stephen Hansen
  m e @ i x o k a i . i o

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#106807 — Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]

On Mon, Apr 11, 2016 at 10:13 AM, Fillmore <fillmore_remove@hotmail.com> wrote:
> Sorry guys. It was not my intention to piss off anyone...just trying to
> understand how the languare works
>
> I guess that the answer to my question is: there is no such thing as a
> one-element tuple,
> and Python will automatically convert a one-element tuple to a string...
> hence the
> behavior I observed is explained...
>
>>>> a = ('hello','bonjour')
>>>> b = ('hello')
>>>> b
> 'hello'
>>>> a
> ('hello', 'bonjour')
>>>>
>
>
> Did I get this right this time?

Okay, now you're asking a question in a reasonable way, so we can answer :)

The thing you're confused at is that it's not the parentheses that
create a tuple. Parentheses merely group.

>>> 'hello', 'bonjour'
('hello', 'bonjour')
>>> 'hello',
('hello',)

One-element tuples are perfectly possible, but you MUST have a comma,
so you have one at the end. The trailing comma is perfectly legal (and
ignored) on larger tuples.

>>> 'hello', 'bonjour',
('hello', 'bonjour')

ChrisA

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#106808 — Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]

On 04/10/2016 08:13 PM, Fillmore wrote:
>
> Sorry guys. It was not my intention to piss off anyone...just trying to understand how the languare works
>
> I guess that the answer to my question is: there is no such thing as a one-element tuple,
> and Python will automatically convert a one-element tuple to a string... hence the
> behavior I observed is explained...
>
>  >>> a = ('hello','bonjour')
>  >>> b = ('hello')
>  >>> b
> 'hello'
>  >>> a
> ('hello', 'bonjour')
>  >>>


Hold on a sec! it turns up that there is such thing as single-element tuples in python:

 >>> c = ('hello',)
 >>> c
('hello',)
 >>> c[0]
'hello'
 >>> c[1]
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
IndexError: tuple index out of range
 >>>

So, my original question makes sense. Why was a discontinuation point introduced by the language designer?

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#106809 — Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]

On Sun, Apr 10, 2016, at 05:22 PM, Fillmore wrote:
> Hold on a sec! it turns up that there is such thing as single-element
> tuples in python:
> 
>  >>> c = ('hello',)
>  >>> c
> ('hello',)
>  >>> c[0]
> 'hello'
>  >>> c[1]
> Traceback (most recent call last):
>    File "<stdin>", line 1, in <module>
> IndexError: tuple index out of range
>  >>>
> 
> So, my original question makes sense. Why was a discontinuation point
> introduced by the language designer?

What discontinuation point? 

You keep masterfully managing to *not explain what you're asking*. What
is surprising to you? 

--S

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#106813 — Re: one-element tuples

Fillmore <fillmore_remove@hotmail.com> writes:

> So, my original question makes sense. Why was a discontinuation point
> introduced by the language designer?

Can you describe explicitly what that “discontinuation point” is? I'm
not seeing it.

-- 
 \           “People are very open-minded about new things, as long as |
  `\         they're exactly like the old ones.” —Charles F. Kettering |
_o__)                                                                  |
Ben Finney

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#106816 — Re: one-element tuples

On 04/10/2016 08:31 PM, Ben Finney wrote:
> Can you describe explicitly what that “discontinuation point” is? I'm
> not seeing it.

Here you go:

 >>> a = '"string1"'
 >>> b = '"string1","string2"'
 >>> c = '"string1","string2","string3"'
 >>> ea = eval(a)
 >>> eb = eval(b)
 >>> ec = eval(c)
 >>> type(ea)
<class 'str'>   <--- HERE !!!!
 >>> type(eb)
<class 'tuple'>
 >>> type(ec)
<class 'tuple'>

I can tell you that it exists because it bit me in the butt today...

and mind you, I am not saying that this is wrong. I'm just saying that it surprised me.

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#106818 — Re: one-element tuples

Fillmore <fillmore_remove@hotmail.com> writes:

> Here you go:
>
> >>> a = '"string1"'
> >>> b = '"string1","string2"'
> >>> c = '"string1","string2","string3"'
> >>> ea = eval(a)
> >>> eb = eval(b)
> >>> ec = eval(c)
> >>> type(ea)
> <class 'str'>   <--- HERE !!!!
> >>> type(eb)
> <class 'tuple'>
> >>> type(ec)
> <class 'tuple'>
>
> I can tell you that it exists because it bit me in the butt today...
>
> and mind you, I am not saying that this is wrong. I'm just saying that
> it surprised me.

What behaviour did you expect instead? That's still unclear.

Can you show the fictional session that would result from the behaviour
you expect?

-- 
 \         “Education is learning what you didn't even know you didn't |
  `\                  know.” —Daniel J. Boorstin, historian, 1914–2004 |
_o__)                                                                  |
Ben Finney

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#106878 — Re: one-element tuples

On 2016-04-11, Ben Finney <ben+python@benfinney.id.au> wrote:
> Fillmore <fillmore_remove@hotmail.com> writes:
>>
>> I can tell you that it exists because it bit me in the butt today...
>>
>> and mind you, I am not saying that this is wrong. I'm just saying that
>> it surprised me.
>
> What behaviour did you expect instead? That's still unclear.

I must admit this is one of the best trolls I've seen in a while...

-- 
Grant Edwards               grant.b.edwards        Yow! GOOD-NIGHT, everybody
                                  at               ... Now I have to go
                              gmail.com            administer FIRST-AID to my
                                                   pet LEISURE SUIT!!

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#106879 — Re: one-element tuples

On 04/11/2016 10:10 AM, Grant Edwards wrote:

>> What behaviour did you expect instead? That's still unclear.
>
> I must admit this is one of the best trolls I've seen in a while...
>

shall I take it as a compliment?

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#106882 — Re: one-element tuples

On 2016-04-11, Fillmore <fillmore_remove@hotmail.com> wrote:
> On 04/11/2016 10:10 AM, Grant Edwards wrote:
>
>>> What behaviour did you expect instead? That's still unclear.
>>
>> I must admit this is one of the best trolls I've seen in a while...
>
> shall I take it as a compliment?

That depends on your intent, so only you really know the answer.

-- 
Grant Edwards               grant.b.edwards        Yow! I hope something GOOD
                                  at               came in the mail today so
                              gmail.com            I have a REASON to live!!

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