FiniteSet not Value False

[flavio1974-art]

A=FiniteSet(1,2)
B=(FiniteSet(1,2),FiniteSet(1))

{1} in A
AttributeError Traceback (most recent call last)
in ()
----> 1 {1} in A

/usr/lib/python3/dist-packages/sympy/sets/sets.py in contains(self, other)
577
578 def contains(self, other):
--> 579 symb = sympify(self.contains(other))
580 if not (symb is S.true or symb is S.false):
581 raise TypeError('contains did not evaluate to a bool: %r' % symb)

/usr/lib/python3/dist-packages/sympy/sets/sets.py in contains(self, other)
305 """
306 other = sympify(other, strict=True)
--> 307 ret = sympify(self._contains(other))
308 if ret is None:
309 ret = Contains(other, self, evaluate=False)

/usr/lib/python3/dist-packages/sympy/sets/sets.py in _contains(self, other)
2001 r = false
2002 for e in self._elements:
-> 2003 t = Eq(e, other, evaluate=True)
2004 if isinstance(t, Eq):
2005 t = t.simplify()

/usr/lib/python3/dist-packages/sympy/core/relational.py in new(cls, lhs, rhs, **options)
302 return r
303 if hasattr(rhs, '_eval_Eq'):
--> 304 r = rhs._eval_Eq(lhs)
305 if r is not None:
306 return r

/usr/lib/python3/dist-packages/sympy/sets/sets.py in _eval_Eq(self, other)
1899
1900 def _eval_Eq(self, other):
-> 1901 if not other.is_FiniteSet:
1902 if (other.is_Union or other.is_Complement or
1903 other.is_Intersection or other.is_Produ

[flavio1974-art]

[friyaz]

Hi! Can you please clarify the issue further?

[oscarbenjamin]

This is what I get with sympy 1.6.2:

In [8]: A = FiniteSet(1, 2)                                                                                                                    

In [9]: B = FiniteSet(FiniteSet(1, 2), FiniteSet(1))                                                                                           

In [10]: A                                                                                                                                     
Out[10]: {1, 2}

In [11]: B                                                                                                                                     
Out[11]: {{1}, {1, 2}}

In [12]: A in B                                                                                                                                
Out[12]: True

In [15]: 1 in A                                                                                                                                
Out[15]: True

In [13]: print(A.issubset(B)) # should be False                                                                                                
None

In [14]: 1 in B           # should be False                                                                                                                     
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-14-858aaa7d4c4d> in <module>
----> 1 1 in B

~/current/sympy/sympy/sympy/sets/sets.py in __contains__(self, other)
    673             # x in y must evaluate to T or F; to entertain a None
    674             # result with Set use y.contains(x)
--> 675             raise TypeError('did not evaluate to a bool: %r' % c)
    676         return b
    677 

TypeError: did not evaluate to a bool: None

These would evaluate correctly if Eq could recognise that a Set is never equal to an Expr:

In [11]: Eq(1, FiniteSet(1, 2))                                                                                                                
Out[11]: 1 = {1, 2}

In [12]: Eq(1, FiniteSet(1))                                                                                                                   
Out[12]: 1 = {1}