Modify Symbol to add assumptions to global assumptions

symbol.diff

commit de49998cc22c1873799539237d6202134a463956
Author: Sudhanshu Mishra <[email protected]>
Date:   Tue Jun 23 16:35:13 2015 +0530

    Symbol creation adds provided assumptions to global assumptions

diff --git a/sympy/core/symbol.py b/sympy/core/symbol.py
index 3945fa1..45be26d 100644
--- a/sympy/core/symbol.py
+++ b/sympy/core/symbol.py
@@ -96,8 +96,41 @@ def __new__(cls, name, **assumptions):
         False
 
         """
+        from sympy.assumptions.assume import global_assumptions
+        from sympy.assumptions.ask import Q
+
         cls._sanitize(assumptions, cls)
-        return Symbol.__xnew_cached_(cls, name, **assumptions)
+        sym = Symbol.__xnew_cached_(cls, name, **assumptions)
+
+        items_to_remove = []
+        # Remove previous assumptions on the symbol with same name.
+        # Note: This doesn't check expressions e.g. Q.real(x) and
+        # Q.positive(x + 1) are not contradicting.
+        for assumption in global_assumptions:
+            if isinstance(assumption.arg, cls):
+                if str(assumption.arg) == name:
+                    items_to_remove.append(assumption)
+
+        for item in items_to_remove:
+            global_assumptions.remove(item)
+
+        for key, value in assumptions.items():
+            if not hasattr(Q, key):
+                continue
+            # Special case to handle commutative key as this is true
+            # by default
+            if key == 'commutative':
+                if not assumptions[key]:
+                    global_assumptions.add(~getattr(Q, key)(sym))
+                continue
+
+            if value:
+                global_assumptions.add(getattr(Q, key)(sym))
+            elif value is False:
+                global_assumptions.add(~getattr(Q, key)(sym))
+
+        return sym
+
 
     def __new_stage2__(cls, name, **assumptions):
         if not isinstance(name, string_types):


Master

In [1]: from sympy import *
In [2]: %time x = Symbol('x', positive=True, real=True, integer=True)
CPU times: user 233 µs, sys: 29 µs, total: 262 µs
Wall time: 231 µs


This branch

In [1]: from sympy import *
In [2]: %time x = Symbol('x', positive=True, real=True, integer=True)
CPU times: user 652 µs, sys: 42 µs, total: 694 µs
Wall time: 657 µs