Fix the latex representation of a 1-tuple

Without this change, a 1-item tuple looks like a set of parentheses, which is misleading.
This adds the trailing comma (or as appropriate, semicolon) that is typical of 1-tuples in python.

sympy/interactive/tests/test_ipythonprinting.py

@@ -134,7 +134,7 @@ def test_builtin_containers():
 ([ ],)
  [2]  \
 """
-        assert app.user_ns['c']['text/latex'] == '$\\displaystyle \\left( \\left[\\begin{matrix}1\\\\2\\end{matrix}\\right]\\right)$'
+        assert app.user_ns['c']['text/latex'] == '$\\displaystyle \\left( \\left[\\begin{matrix}1\\\\2\\end{matrix}\\right],\\right)$'
     else:
         assert app.user_ns['a'][0]['text/plain'] ==  '(True, False)'
         assert 'text/latex' not in app.user_ns['a'][0]
@@ -146,7 +146,7 @@ def test_builtin_containers():
 ([ ],)
  [2]  \
 """
-        assert app.user_ns['c'][0]['text/latex'] == '$\\displaystyle \\left( \\left[\\begin{matrix}1\\\\2\\end{matrix}\\right]\\right)$'
+        assert app.user_ns['c'][0]['text/latex'] == '$\\displaystyle \\left( \\left[\\begin{matrix}1\\\\2\\end{matrix}\\right],\\right)$'
 
 def test_matplotlib_bad_latex():
     # Initialize and setup IPython session

sympy/printing/latex.py

@@ -209,6 +209,10 @@ def __init__(self, settings=None):
     def _add_parens(self, s):
         return r"\left({}\right)".format(s)
 
+    # TODO: merge this with the above, which requires a lot of test changes
+    def _add_parens_lspace(self, s):
+        return r"\left( {}\right)".format(s)
+
     def parenthesize(self, item, level, is_neg=False, strict=False):
         prec_val = precedence_traditional(item)
         if is_neg and strict:
@@ -1865,15 +1869,20 @@ def _print_frac(self, expr, exp=None):
                     self._print(expr.args[0]), self._print(exp))
 
     def _print_tuple(self, expr):
-        if self._settings['decimal_separator'] =='comma':
-            return r"\left( %s\right)" % \
-                r"; \  ".join([self._print(i) for i in expr])
-        elif self._settings['decimal_separator'] =='period':
-            return r"\left( %s\right)" % \
-                r", \  ".join([self._print(i) for i in expr])
+        if self._settings['decimal_separator'] == 'comma':
+            sep = ";"
+        elif self._settings['decimal_separator'] == 'period':
+            sep = ","
         else:
             raise ValueError('Unknown Decimal Separator')
 
+        if len(expr) == 1:
+            # 1-tuple needs a trailing separator
+            return self._add_parens_lspace(self._print(expr[0]) + sep)
+        else:
+            return self._add_parens_lspace(
+                (sep + r" \  ").join([self._print(i) for i in expr]))
+
     def _print_TensorProduct(self, expr):
         elements = [self._print(a) for a in expr.args]
         return r' \otimes '.join(elements)

sympy/printing/tests/test_latex.py

@@ -2567,16 +2567,19 @@ def test_latex_decimal_separator():
     assert(latex([1, 2.3, 4.5], decimal_separator='comma') == r'\left[ 1; \  2{,}3; \  4{,}5\right]')
     assert(latex(FiniteSet(1, 2.3, 4.5), decimal_separator='comma') == r'\left\{1; 2{,}3; 4{,}5\right\}')
     assert(latex((1, 2.3, 4.6), decimal_separator = 'comma') == r'\left( 1; \  2{,}3; \  4{,}6\right)')
+    assert(latex((1,), decimal_separator='comma') == r'\left( 1;\right)')
 
     # period decimal_separator
     assert(latex([1, 2.3, 4.5], decimal_separator='period') == r'\left[ 1, \  2.3, \  4.5\right]' )
     assert(latex(FiniteSet(1, 2.3, 4.5), decimal_separator='period') == r'\left\{1, 2.3, 4.5\right\}')
     assert(latex((1, 2.3, 4.6), decimal_separator = 'period') == r'\left( 1, \  2.3, \  4.6\right)')
+    assert(latex((1,), decimal_separator='period') == r'\left( 1,\right)')
 
     # default decimal_separator
     assert(latex([1, 2.3, 4.5]) == r'\left[ 1, \  2.3, \  4.5\right]')
     assert(latex(FiniteSet(1, 2.3, 4.5)) == r'\left\{1, 2.3, 4.5\right\}')
     assert(latex((1, 2.3, 4.6)) == r'\left( 1, \  2.3, \  4.6\right)')
+    assert(latex((1,)) == r'\left( 1,\right)')
 
     assert(latex(Mul(3.4,5.3), decimal_separator = 'comma') ==r'18{,}02')
     assert(latex(3.4*5.3, decimal_separator = 'comma')==r'18{,}02')