Sets printing issues

[asmeurer]

Some issues with str and srepr printing in sets.

Some notes:

• The str printer should always generate valid Python, which recreates the expression (but may require some variables to be defined).
• The srepr printer should generate an expression that recreates the expression exactly, using only the names from from sympy import * (or other relevant imports for other submodules, but that isn't relevant for the sets).
• Fancy printing should be relegated to the pretty printers (pprint and latex).

Here are the issues I found:

1. str(Interval)

   In [9]: str(Interval(0, 1, False))
   Out[9]: '[0, 1]'
   
   In [10]: str(Interval(0, 1, True))
   Out[10]: '(0, 1]'
   

   The former creates a list, not an interval. The latter isn't even valid Python.

2. srepr(S.Integers) (and probably others)

   In [11]: srepr(S.Integers)
   Out[11]: 'Integers()'
   

   Integers isn't a name that is imported from sympy. It should print as S.Integers. The str printers should probably do the same.

3. str(Union)

   In [18]: str(Union(S.Integers, FiniteSet(pi))) 
   Out[18]: 'Integers() U {pi}'
   

   It's not valid Python. It should print as Union(S.Integers, FiniteSet(pi)). Printing as Union(S.Integers, {pi}) is fine when sympify(set) should give FiniteSet #10654 gets merged.

There are likely others. I didn't check too much. An audit of the printing in the sets module would be worthwhile.

[parvparkhiya]

I would like to work on this.

[SalilVishnuKapur]

@asmeurer Regarding the issue 1 . I find it outputs something else on the sympy live shell . Kindly have a look .

str(Interval(0, 1, False))
[0,1]

str(Interval(0, 1, True))
(0,1]

Also,

type(str(Interval(0, 1, False)))
<type′str′>

type(str(Interval(0, 1, true)))
<type′str′>

[AnishShah]

The output is the same on sympy live

[SalilVishnuKapur]

@AnishShah but here have a look at this screenshot of what i tried on sympy live.

If I am going wrong somewhere then kindly guide.

[AnishShah]

I'm sorry if I'm missing something, but the output in your screenshot is same as the output mentioned by @asmeurer. I don't see any difference.

[SalilVishnuKapur]

'[0, 1]' and [0, 1] . I think it is already a string after getting evaluated by str.

[asmeurer]

@SalilVishnuKapur that's because the SymPy Live shell renders the output as LaTeX.

You should work locally against the git master. SymPy Live has some differences against the normal SymPy which might confuse, but more importantly, it runs SymPy 0.7.6, whereas you want to work against the git master.

[theaverageguy]

I would like to take this up. :)

[wrat]

I also want to work on this but i am new here so how should start?

[asmeurer]

It looks like this has already been started at #10708, so you should at least wait until that is merged and see if anything is left to do then.

[asmeurer]

Also see https://github.com/sympy/sympy/wiki/Development-workflow for general instructions on how to contribute.

[wrat]

Ohkk thanks Aaron Meurer!!! I will wait for that or I will work on other Issue. Thanks for suggestion.

[asmeurer]

Related #10035

[SagarB-97]

@asmeurer
Please review PR #12112

[Upabjojr]

#12213

[asmeurer]

@Upabjojr wrong number? I don't see how that's related.

[Upabjojr]

wrong number? I don't see how that's related.

Sorry, I wanted to link the issue of the And and Or str() printer.

[SagarB-97]

Please review #12112

[SagarB-97]

@Upabjojr I don't think this issue should be closed. #12112 takes care of only str printer. srepr printer is still the same.

[Upabjojr]

@SagarB-97 github apparently closed the issue automatically, I didn't actually notice that.

[AnimeshSinha1309]

Is this the expected behaviour of str() and srepr():

>>> from sympy import S
>>> from sympy import srepr
>>> print(S.Integers)
S.Integers
>>> S.Naturals0
S.Naturals0
>>> srepr(S.Naturals)
'S.Naturals'
>>> str(S.Reals)
'S.Reals'

I implemented this but then did not pass the tests as the examples and tests are written for the previous output. Please tell me if this is what was desired so I can fix the tests and examples for the new output.

[asmeurer]

It looks like points 1 and 3 are now fixed. It is no longer necessary to print the fancy sets with S. because they are included in from sympy import * now.

However, this is still wrong:

>>> srepr(Integers)
Integers()

because Integers() raises a TypeError. It should just return "Integers", the same as str.

[AnimeshSinha1309]

Thanks, will fix srepr().