diff --git a/mapytex/calculus/API/expression.py b/mapytex/calculus/API/expression.py
index abb0044..315b303 100644
--- a/mapytex/calculus/API/expression.py
+++ b/mapytex/calculus/API/expression.py
@@ -41,14 +41,38 @@ class Expression(object):
         self._ancestor = ancestor
 
     @classmethod
-    def from_str(cls,  string):
+    def from_str(cls, string, typing=True):
         """ Initiate the expression from a string
 
         :param string: String to parse to generate the Expression
         :returns: the expression
 
+        :example:
+        >>> e = Expression.from_str("2 + 3 * 4")
+        >>> e
+        <Exp: 2 + 3 * 4>
+        >>> e = Expression.from_str("2/3")
+        >>> e
+        <Fraction 2 / 3>
+        >>> e = Expression.from_str("2x + 1")
+        >>> e
+        <Linear 2x + 1>
+        >>> e = Expression.from_str("2x + 1 + 5x^2")
+        >>> e
+        <Quadratic 2x + 1 + 5x^2>
+        >>> e = Expression.from_str("2x + 1 + 5x")
+        >>> e
+        <Exp: 2x + 1 + 5x>
+
         """
         t = Tree.from_str(string)
+        if typing:
+            tt = cls(t)._typing()
+            try:
+                return factory(tt)
+            except TypeError as e:
+                return cls(t)
+
         return cls(t)
 
     @classmethod
@@ -173,7 +197,7 @@ class Expression(object):
         """ Build a copy of self with as much typing as possible
         
         :example:
-        >>> e = Expression.from_str("2x")
+        >>> e = Expression.from_str("2x", typing=False)
         >>> print(e._tree.map_on_leaf(type))
         *
          > <class 'mapytex.calculus.core.MO.mo.MOnumber'>
@@ -185,7 +209,7 @@ class Expression(object):
         >>> print(type(typed_e._tree))
         <class 'mapytex.calculus.core.MO.monomial.MOMonomial'>
 
-        >>> e = Expression.from_str("2x+3+4/5")
+        >>> e = Expression.from_str("2x+3+4/5", typing=False)
         >>> print(e._tree.map_on_leaf(type))
         +
          > +