diff --git a/pymath/__init__.py b/pymath/__init__.py
index 44cea70..c12f1ed 100644
--- a/pymath/__init__.py
+++ b/pymath/__init__.py
@@ -7,4 +7,4 @@ from .stat import Dataset, WeightedDataset
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/__init__.py b/pymath/calculus/__init__.py
index 4e0ba5f..414e13e 100644
--- a/pymath/calculus/__init__.py
+++ b/pymath/calculus/__init__.py
@@ -11,4 +11,4 @@ from .render import txt
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/abstract_polynom.py b/pymath/calculus/abstract_polynom.py
index 6faab70..b0ffaf0 100644
--- a/pymath/calculus/abstract_polynom.py
+++ b/pymath/calculus/abstract_polynom.py
@@ -71,7 +71,7 @@ class AbstractPolynom(Explicable):
         self.feed_coef(coefs)
         self._letter = letter
         self.name = name
-        
+
         if self.is_monom():
             self.mainOp = op.mul
         else:
@@ -81,7 +81,7 @@ class AbstractPolynom(Explicable):
 
     def feed_coef(self, l_coef):
         """Feed coef of the polynom. Manage differently whether it's a number or an expression
-        
+
         :l_coef: list of coef
         """
         self._coef = []
@@ -156,16 +156,16 @@ class AbstractPolynom(Explicable):
         ['x', 2, '^']
 
         """
-        ans =[] 
+        ans =[]
         if a == [0]:
             pass
         elif i == 0:
             ans = a
         elif i == 1:
-            ans = a * (a!=[1]) + [self._letter] + [op.mul] *  (a!=[1]) 
+            ans = a * (a!=[1]) + [self._letter] + [op.mul] *  (a!=[1])
         else:
-            ans = a * (a!=[1]) + [self._letter, i, op.pw] + [op.mul] *  (a!=[1]) 
-        
+            ans = a * (a!=[1]) + [self._letter, i, op.pw] + [op.mul] *  (a!=[1])
+
         return ans
 
     @property
@@ -276,13 +276,13 @@ class AbstractPolynom(Explicable):
 
     def conv2poly(self, other):
         """Convert anything number into a polynom
-        
+
         >>> P = AbstractPolynom([1,2,3])
         >>> P.conv2poly(1)
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [1]>
         >>> P.conv2poly(0)
         < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [0]>
-        
+
         """
         if isNumber(other) and not isPolynom(other):
             return AbstractPolynom([other], letter = self._letter)
@@ -290,7 +290,7 @@ class AbstractPolynom(Explicable):
             return other
         else:
             raise ValueError(type(other) + " can't be converted into a polynom")
-    
+
     def reduce(self):
         """Compute coefficients which have same degree
 
@@ -315,7 +315,7 @@ class AbstractPolynom(Explicable):
         >>> Q.steps
         [< <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [[1, 2], [3, 4, 5], 6]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [< <class 'pymath.calculus.expression.Expression'> [1, 2, '+'] >, < <class 'pymath.calculus.expression.Expression'> [3, 4, '+', 5, '+'] >, 6]>, < <class 'pymath.calculus.abstract_polynom.AbstractPolynom'> [3, < <class 'pymath.calculus.expression.Expression'> [7, 5, '+'] >, 6]>]
         """
-    
+
         # TODO: It doesn't not compute quick enough |ven. févr. 27 18:04:01 CET 2015
 
         # gather steps for every coefficients
@@ -368,7 +368,7 @@ class AbstractPolynom(Explicable):
 
         ans, steps = steps[-1], steps[:-1]
         ans.steps = steps
-            
+
         return ans
 
     def simplify(self):
@@ -378,7 +378,7 @@ class AbstractPolynom(Explicable):
     @staticmethod
     def postfix_add(numbers):
         """Convert a list of numbers into a postfix addition
-        
+
         :numbers: list of numbers
         :returns: Postfix list of succecive attition of number
 
@@ -400,7 +400,7 @@ class AbstractPolynom(Explicable):
         else:
             ans = [[a, op.add] if i!=0 else [a] for (i,a) in enumerate(numbers)]
             return list(chain.from_iterable(ans))
-            
+
     def __eq__(self, other):
         try:
             o_poly = self.conv2poly(other)
@@ -409,7 +409,7 @@ class AbstractPolynom(Explicable):
             return 0
 
     def __add__(self, other):
-        """ Overload + 
+        """ Overload +
 
         >>> P = AbstractPolynom([1,2,3])
         >>> Q = AbstractPolynom([4,5])
@@ -484,9 +484,9 @@ class AbstractPolynom(Explicable):
 
     def __rsub__(self, other):
         o_poly = self.conv2poly(other)
-        
+
         return o_poly.__sub__(self)
-    
+
     def __mul__(self, other):
         """ Overload *
 
@@ -549,7 +549,7 @@ class AbstractPolynom(Explicable):
         o_poly = self.conv2poly(other)
 
         return o_poly.__mul__(self)
-        
+
     @power_cache
     def __pow__(self, power):
         """ Overload **
@@ -612,4 +612,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/arithmetic.py b/pymath/calculus/arithmetic.py
index 98fee2e..5508139 100644
--- a/pymath/calculus/arithmetic.py
+++ b/pymath/calculus/arithmetic.py
@@ -41,4 +41,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/explicable.py b/pymath/calculus/explicable.py
index fb91efd..fe5c6c0 100644
--- a/pymath/calculus/explicable.py
+++ b/pymath/calculus/explicable.py
@@ -71,23 +71,23 @@ class Renderable(object):
         except AttributeError:
             return False
 
-    
-        
+
+
 class Explicable(Renderable):
 
     """ An Explicable object is an object which can be explicable!
-    
+
     It's a parent class of a more classical Expression, Fraction and Polynom (and later square root)
     Child class will have the following method
         * explain: Generator which return steps which leed to himself
-    
+
     """
     def __init__(self, *args, **kwargs):
         self.steps = []
 
     def explain(self, noself = True):
         """ Generate and render steps  which leed to itself
-        
+
         :param noself: does explain return self
 
         """
@@ -125,11 +125,11 @@ class Explicable(Renderable):
             else:
                 return False
 
-        
+
 
 
 
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/expression.py b/pymath/calculus/expression.py
index b4aa488..87f9f5c 100644
--- a/pymath/calculus/expression.py
+++ b/pymath/calculus/expression.py
@@ -22,7 +22,7 @@ class Fake_int(int, Explicable):
         self.steps = []
     def simplify(self):
         return Fake_int(self._val)
-        
+
 
 class Expression(Explicable):
     """A calculus expression. Today it can andle only expression with numbers later it will be able to manipulate unknown"""
@@ -88,7 +88,7 @@ class Expression(Explicable):
         expression = object.__new__(cls)
 
         if type(exp) == str:
-            expression.postfix_tokens = str2tokens(exp) 
+            expression.postfix_tokens = str2tokens(exp)
 
         elif type(exp) == list:
             # Ici on ne peut convertir les "+" en opérateur que s'ils sont d'arité 2.
@@ -96,7 +96,7 @@ class Expression(Explicable):
             expression.postfix_tokens = flatten_list([tok.postfix_tokens if Expression.isExpression(tok) else tok for tok in exp_mod_op])
 
         elif type(exp) == Expression:
-            return exp 
+            return exp
 
         elif isNumerand(exp):
             expression.postfix_tokens = [exp]
@@ -156,16 +156,16 @@ class Expression(Explicable):
         tokenList = self.postfix_tokens.copy()
         tmpTokenList = []
 
-        while len(tokenList) > 2: 
-            # on va chercher les motifs du genre A B +, quand l'operateur est d'arité 2, pour les calculer 
+        while len(tokenList) > 2:
+            # on va chercher les motifs du genre A B +, quand l'operateur est d'arité 2, pour les calculer
             if isNumerand(tokenList[0]) and isNumerand(tokenList[1]) \
                     and isOperator(tokenList[2]) and tokenList[2].arity == 2 :
-                
+
                 # S'il y a une opération à faire
                 op1 = tokenList[0]
                 op2 = tokenList[1]
                 operator = tokenList[2]
-                
+
                 res = operator(op1, op2)
 
                 tmpTokenList.append(res)
@@ -176,7 +176,7 @@ class Expression(Explicable):
             # Et les motifs du gens A -, quand l'operateur est d'arité 1
             elif isNumerand(tokenList[0]) \
                     and isOperator(tokenList[1]) and tokenList[1].arity == 1:
-                
+
                 # S'il y a une opération à faire
                 op1 = tokenList[0]
                 operator = tokenList[1]
@@ -261,7 +261,7 @@ class Expression(Explicable):
             return Expression(self.postfix_tokens + other + [operator])
         else:
             return Expression(self.postfix_tokens + [other] + [operator])
-    
+
     def roperate(self, other, operator):
         if type(other) == Expression:
             return Expression(other.postfix_tokens + self.postfix_tokens + [operator])
@@ -336,7 +336,7 @@ class Expression(Explicable):
         >>> c = a / b
         >>> print(c.postfix_tokens)
         [1, 2, '+', 3, 4, '+', '/']
-        >>> 
+        >>>
         """
         return self.operate(other, op.div)
 
@@ -351,7 +351,7 @@ class Expression(Explicable):
 
     def __neg__(self):
         return Expression(self.postfix_tokens + [op.sub1])
-    
+
 
 def untest(exp):
     a = Expression(exp)
@@ -376,7 +376,7 @@ if __name__ == '__main__':
     #    print(i)
 
     #print(type(Ar))
-    
+
 
     #print('\n-----------')
     #A = Expression("-6 / 3 + 10 / -5")
@@ -396,4 +396,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/fraction.py b/pymath/calculus/fraction.py
index f7fa92f..e1dace7 100644
--- a/pymath/calculus/fraction.py
+++ b/pymath/calculus/fraction.py
@@ -31,7 +31,7 @@ class Fraction(Explicable):
         self.isNumber = 1
 
     def simplify(self):
-        """Simplify the fraction 
+        """Simplify the fraction
 
         :returns: steps to simplify the fraction or the fraction if there is nothing to do
 
@@ -133,7 +133,7 @@ class Fraction(Explicable):
             number = Fraction(other)
 
         return number
-    
+
     def __add__(self, other):
         """ overload +
 
@@ -276,7 +276,7 @@ class Fraction(Explicable):
         ans =  f.simplify()
 
         return ans
-    
+
     def __mul__(self, other):
         """ overload *
 
@@ -330,18 +330,18 @@ class Fraction(Explicable):
         else:
             number = self.convert2fraction(other)
 
-            gcd1 = gcd(self._num, number._denom) 
+            gcd1 = gcd(self._num, number._denom)
             if gcd1 != 1:
                 num1 = [int(self._num/ gcd1), gcd1, op.mul]
-                denom2 = [int(number._denom/ gcd1), gcd1, op.mul] 
+                denom2 = [int(number._denom/ gcd1), gcd1, op.mul]
             else:
                 num1 = [self._num]
                 denom2 = [number._denom]
 
-            gcd2 = gcd(self._denom, number._num) 
+            gcd2 = gcd(self._denom, number._num)
             if gcd2 != 1:
                 num2 = [int(number._num/ gcd2), gcd2, op.mul]
-                denom1 = [int(self._denom/ gcd2), gcd2, op.mul] 
+                denom1 = [int(self._denom/ gcd2), gcd2, op.mul]
             else:
                 num2 = [number._num]
                 denom1 = [self._denom]
@@ -396,7 +396,7 @@ class Fraction(Explicable):
 
     def __pow__(self, power):
         """ overload **
-        
+
         >>> f = Fraction(3, 4)
         >>> f**0
         1
@@ -419,7 +419,7 @@ class Fraction(Explicable):
         < <class 'pymath.calculus.expression.Expression'> [6, 3, '^', 4, 3, '^', '/'] >
         < <class 'pymath.calculus.expression.Expression'> [216, 64, '/'] >
         < <class 'pymath.calculus.expression.Expression'> [27, 8, '*', 8, 8, '*', '/'] >
-        
+
         """
         if not type(power) == int:
             raise ValueError("Can't raise fraction to power {}".format(str(power)))
@@ -449,7 +449,7 @@ class Fraction(Explicable):
         >>> f^3
         < Fraction 27 / 64>
         """
-        
+
         return self.__pow__(power)
 
     def __abs__(self):
@@ -557,4 +557,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/generic.py b/pymath/calculus/generic.py
index 3607ad9..98b7780 100644
--- a/pymath/calculus/generic.py
+++ b/pymath/calculus/generic.py
@@ -242,7 +242,7 @@ def convolution_dict(D1, D2, op = lambda x,y:x*y,\
 
 def spe_zip(l1,l2):
     """Zip two lists, if a list is longer, only it's element are taken
-    
+
     >>> spe_zip([1,2], [3,4])
     [[1, 3], [2, 4]]
     >>> spe_zip([1,2], [3,4,5])
@@ -260,7 +260,7 @@ def spe_zip(l1,l2):
 
 def transpose_fill(list_lists):
     """Transpose a list of list and if inside list have not the same length, fill with last token
-    
+
     :list_lists: a list of list to transpose
     :returns: generator which generate lines of the transposed matrix
 
@@ -274,7 +274,7 @@ def transpose_fill(list_lists):
                 col.append(l[i])
             except IndexError:
                 col.append(l[-1])
-        
+
         yield col
 
 def isOperator(exp):
@@ -284,7 +284,7 @@ def isOperator(exp):
     :returns: boolean
 
     """
-    
+
     #return (type(exp) == str and exp in "+-*/:^")
     try:
         exp.isOperator
@@ -358,4 +358,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/operator.py b/pymath/calculus/operator.py
index b83e2a8..01cdee9 100644
--- a/pymath/calculus/operator.py
+++ b/pymath/calculus/operator.py
@@ -66,7 +66,7 @@ class Operator(str):
 
     def __txt__(self, *args):
         """Txt rendering for the operator
-        
+
         :*args: Operands for this operation
         :returns: String with operator and his operands
 
@@ -90,7 +90,7 @@ class Operator(str):
 
     def __tex__(self, *args):
         """Tex rendering for the operator
-        
+
         :*args: Operands for this operation
         :returns: String with operator and his operands
 
@@ -114,7 +114,7 @@ class Operator(str):
 
     def __p2i__(self, *args):
         """Fix list transformation for the operator
-        
+
         :*args: Operands for this operation
         :returns: list with the operator surrounded by operands
 
@@ -140,7 +140,7 @@ class Operator(str):
             op1 = self.l_parenthesis(args[0])
             op2 = self.r_parenthesis(args[1])
             ans = flatten_list([op1, self, op2])
-        
+
         ans = save_mainOp(ans, self)
         return ans
 
@@ -181,7 +181,7 @@ class Operator(str):
 
 def save_mainOp(obj, mainOp):
     """Create a temporary class build over built-in type to stock the main operation of a calculus
-    
+
     :obj: the object to add the attribute
     :mainOp: the main operator
     :returns: the same object with the main operation attribute
@@ -251,9 +251,9 @@ class op(object):
     @operatorize
     def add(cls):
         """ The operator +
-        
+
         For doctest see test/test_operator.py
-        
+
         """
 
         def _render(self, link, *args):
@@ -296,7 +296,7 @@ class op(object):
     @operatorize
     def sub(self):
         """ The operator -
-        
+
         >>> sub = op.sub
         >>> sub
         '-'
@@ -350,7 +350,7 @@ class op(object):
     @operatorize
     def sub1(self):
         """ The operator -
-        
+
         >>> sub1 = op.sub1
         >>> sub1
         '-'
@@ -398,7 +398,7 @@ class op(object):
     @operatorize
     def mul(self):
         """ The operator *
-        
+
         >>> mul = op.mul
         >>> mul
         '*'
@@ -475,7 +475,7 @@ class op(object):
     @operatorize
     def div(self):
         """ The operator /
-        
+
         >>> div = op.div
         >>> div
         '/'
@@ -498,7 +498,7 @@ class op(object):
         def __tex__(self, *args):
             # Pas besoin de parenthèses en plus pour \frac
             replacement = {"op"+str(i+1): op for (i,op) in enumerate(args)}
-            
+
             ans = self.tex.format(**replacement)
             ans = save_mainOp(ans, self)
             return ans
@@ -520,7 +520,7 @@ class op(object):
     @operatorize
     def pw(self):
         """ The operator ^
-        
+
         >>> pw = op.pw
         >>> pw
         '^'
@@ -586,7 +586,7 @@ class op(object):
     @classmethod
     def get_op(cls, op, arity = 2):
         """Return the corresponding operator
-        
+
         :op: symbole of the op
         :arity: the arity
 
@@ -643,4 +643,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/polynom.py b/pymath/calculus/polynom.py
index af6d34d..c59d5eb 100644
--- a/pymath/calculus/polynom.py
+++ b/pymath/calculus/polynom.py
@@ -34,7 +34,7 @@ def polynom_factory(func):
 class Polynom(AbstractPolynom):
 
     """Polynom view as a function.
-    
+
     It can be initiate like a AbstractPolynom
     # Put example
     Randomly
@@ -48,10 +48,10 @@ class Polynom(AbstractPolynom):
 
     @classmethod
     def random(self, coefs_form=[], conditions=[], letter = "x", degree = 0, name = "P"):
-        """ Create a random polynom from coefs_form and conditions 
+        """ Create a random polynom from coefs_form and conditions
 
         :param coefs_form: list of forms (one by coef) (ascending degree sorted)
-        :param conditions: condition on variables 
+        :param conditions: condition on variables
         :param letter: the letter for the polynom
         :param degree: degree of the polynom (can't be used with coefs_form, it will be overwrite) - can't be higher than 26 (number of letters in alphabet)
 
@@ -146,8 +146,8 @@ class Polynom(AbstractPolynom):
         return Expression(postfix_exp).simplify()
 
     def derivate(self):
-        """ Return the derivated polynom 
-        
+        """ Return the derivated polynom
+
         >>> P = Polynom([1, 2, 3])
         >>> Q = P.derivate()
         >>> Q
@@ -169,7 +169,7 @@ class Polynom(AbstractPolynom):
 
 # Decorate methods which may return Polynoms
 methods_list = ["__add__", "__call__", "__mul__", "__neg__", "__pow__",
-        "__radd__", "__rmul__", "__rsub__", "__sub__", "derivate", 
+        "__radd__", "__rmul__", "__rsub__", "__sub__", "derivate",
         "reduce", "simplify", "random"]
 for name, func in inspect.getmembers(Polynom):
     if name in methods_list:
@@ -228,7 +228,7 @@ if __name__ == '__main__':
     print("-----------------\n")
     f = Fraction(2,3)
     print(P(f))
-    #coefs_p = [[(i-2),(j-2)] for i,j in permutations(range(20),2)] 
+    #coefs_p = [[(i-2),(j-2)] for i,j in permutations(range(20),2)]
     #fractions = [Fraction(i,j) for i,j in coefs_p if j!=0]
     #for f in fractions:
     #    try:
@@ -241,4 +241,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/polynomDeg2.py b/pymath/calculus/polynomDeg2.py
index ecf88ca..9773f47 100644
--- a/pymath/calculus/polynomDeg2.py
+++ b/pymath/calculus/polynomDeg2.py
@@ -23,7 +23,7 @@ class Polynom_deg2(Polynom):
         """ Create a 2nd degree poly from coefs_form ans conditions
 
         :param coefs_form: list of forms (one by coef) (ascending degree sorted)
-        :param conditions: condition on variables 
+        :param conditions: condition on variables
         :param letter: the letter for the polynom
 
         """
@@ -83,7 +83,7 @@ class Polynom_deg2(Polynom):
     @property
     def alpha(self):
         """ Compute alpha the abcisse of the extremum
-        
+
         >>> P = Polynom_deg2([1,2,3])
         >>> P.alpha
         < Fraction -1 / 3>
@@ -240,11 +240,11 @@ if __name__ == '__main__':
 
     import doctest
     doctest.testmod()
-        
+
 
 
 
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/random_expression.py b/pymath/calculus/random_expression.py
index 4b7074f..304e8cd 100644
--- a/pymath/calculus/random_expression.py
+++ b/pymath/calculus/random_expression.py
@@ -50,11 +50,11 @@ class RdExpression(object):
         for c in self._conditions:
             c_varia_cond = flatten_list([eval(str(i[0])) for i in pyparsing.nestedExpr('{','}').searchString(c)])
             varia_cond = varia_cond | set(c_varia_cond)
-        
+
         self._2replaced = varia_cond | varia_form
 
         return self._2replaced
-        
+
     def get_letters(self):
         """Find letters in the form
         :returns: list of letters
@@ -90,7 +90,7 @@ class RdExpression(object):
 
         :param val_min: minimum value random generation
         :param val_max: maximum value random generation
-        :returns: an formated random expression 
+        :returns: an formated random expression
 
         """
         return self.raw_str(val_min, val_max)
@@ -171,4 +171,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/render.py b/pymath/calculus/render.py
index 4c58f07..138124a 100644
--- a/pymath/calculus/render.py
+++ b/pymath/calculus/render.py
@@ -10,7 +10,7 @@ class Render(object):
 
     def __init__(self, render):
         """Initiate the render
-        
+
         :param render: function which take an operator and return a function to render the operator with his operands
         """
         self.render = render
@@ -25,12 +25,12 @@ class Render(object):
         """
         operandeStack = Stack()
         for token in postfix_tokens:
-            
+
             if isOperator(token):
                 if token.arity == 1:
-                    
+
                     op1 = operandeStack.pop()
-                    
+
                     operandeStack.push(self.render(token)(op1))
                 elif token.arity == 2:
                     op1 = operandeStack.pop()
@@ -76,21 +76,21 @@ if __name__ == '__main__':
     from .operator import op
     from itertools import permutations
     from pymath import Polynom
-    from pymath import Expression 
+    from pymath import Expression
     from pymath import Fraction
-    coefs_p = [[(i-2),(j-2)] for i,j in permutations(range(5),2)] 
-    coefs_q = [[2*(i-2),2*(j-2)] for i,j in permutations(range(5),2)] 
+    coefs_p = [[(i-2),(j-2)] for i,j in permutations(range(5),2)]
+    coefs_q = [[2*(i-2),2*(j-2)] for i,j in permutations(range(5),2)]
     l_p = [Polynom(i) for i in coefs_p]
     l_q = [Fraction(i,j) for i,j in coefs_q if j!=0]
     operations = [Expression([l_p[i],l_q[j],op.mul]) for i,j in permutations(range(len(l_q)),2)]
     for i in operations:
         print(i)
-    
 
 
 
-    
+
+
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/str2tokens.py b/pymath/calculus/str2tokens.py
index 1271934..60316be 100644
--- a/pymath/calculus/str2tokens.py
+++ b/pymath/calculus/str2tokens.py
@@ -6,7 +6,7 @@ from .operator import op
 
 def str2tokens(exp):
     """ Parse the string into tokens then turn it into postfix form
-    
+
     >>> str2tokens('2+3*4')
     [2, 3, 4, '*', '+']
     >>> str2tokens('2*3+4')
@@ -86,7 +86,7 @@ def str2in_tokens(exp):
 
 def in2post_fix(infix_tokens):
     """ From the infix_tokens list compute the corresponding postfix_tokens list
-    
+
     @param infix_tokens: the infix list of tokens to transform into postfix form.
     @return: the corresponding postfix list of tokens.
 
@@ -115,7 +115,7 @@ def in2post_fix(infix_tokens):
                 postfix_tokens.append(next_op)
                 next_op = opStack.pop()
 
-            # Go back to old arity 
+            # Go back to old arity
             arity_Stack.pop()
             # Raise the arity
             arity = arity_Stack.pop()
@@ -127,7 +127,7 @@ def in2post_fix(infix_tokens):
                 # Set next arity counter
                 arity_Stack.push(0)
             else:
-                arity = arity_Stack.pop() 
+                arity = arity_Stack.pop()
                 token_op = op.get_op(token, arity + 1)
                 # Reset arity to 0 in case there is other operators (the real operation would be "-op.arity + 1")
                 arity_Stack.push(0)
@@ -185,4 +185,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/test/test_arithmetic.py b/pymath/calculus/test/test_arithmetic.py
index 67f559b..435d96a 100644
--- a/pymath/calculus/test/test_arithmetic.py
+++ b/pymath/calculus/test/test_arithmetic.py
@@ -28,5 +28,5 @@ def test_gcd_neg():
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/calculus/test/test_expression.py b/pymath/calculus/test/test_expression.py
index 09713ef..2481b61 100644
--- a/pymath/calculus/test/test_expression.py
+++ b/pymath/calculus/test/test_expression.py
@@ -70,11 +70,11 @@ def test_mul_exp():
 
 def test_neg_exp():
     e = Expression("12- 4")
-    g = -e 
+    g = -e
     assert g.postfix_tokens == [12, 4, '-', '-']
 
 
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/test/test_fraction.py b/pymath/calculus/test/test_fraction.py
index 89c87e0..7e2b8c1 100644
--- a/pymath/calculus/test/test_fraction.py
+++ b/pymath/calculus/test/test_fraction.py
@@ -80,7 +80,7 @@ class TestFraction(unittest.TestCase):
         f = Fraction(2, 3)
         ans = "\\frac{ 2 }{ 3 }"
         self.assertEqual(f.__tex__(), ans)
-    
+
     def test_txt(self):
         f = Fraction(2, 3)
         ans = "2 / 3"
@@ -92,4 +92,4 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/test/test_generic.py b/pymath/calculus/test/test_generic.py
index bfc0838..57af8d9 100644
--- a/pymath/calculus/test/test_generic.py
+++ b/pymath/calculus/test/test_generic.py
@@ -66,11 +66,11 @@ class TestGeneric(unittest.TestCase):
 if __name__ == '__main__':
     unittest.main()
 
-        
+
 
 
 
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/calculus/test/test_operator.py b/pymath/calculus/test/test_operator.py
index 2689122..89d173d 100644
--- a/pymath/calculus/test/test_operator.py
+++ b/pymath/calculus/test/test_operator.py
@@ -84,5 +84,5 @@ def test_pw_render_txt():
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/calculus/test/test_polynom.py b/pymath/calculus/test/test_polynom.py
index 6c23fb3..70da7a1 100644
--- a/pymath/calculus/test/test_polynom.py
+++ b/pymath/calculus/test/test_polynom.py
@@ -185,5 +185,5 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/calculus/test/test_polynomDeg2.py b/pymath/calculus/test/test_polynomDeg2.py
index d867c1f..aa7c653 100644
--- a/pymath/calculus/test/test_polynomDeg2.py
+++ b/pymath/calculus/test/test_polynomDeg2.py
@@ -27,5 +27,5 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/calculus/test/test_random_expression.py b/pymath/calculus/test/test_random_expression.py
index ed986d2..b8beba5 100644
--- a/pymath/calculus/test/test_random_expression.py
+++ b/pymath/calculus/test/test_random_expression.py
@@ -14,8 +14,8 @@ def test_only_form():
     assert rdExp._2replaced == {'a'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()) == {'a'} 
-    assert set(rdExp._gene_2replaced.keys()) == {'a'} 
+    assert set(rdExp._gene_varia.keys()) == {'a'}
+    assert set(rdExp._gene_2replaced.keys()) == {'a'}
 
 def test_form_with_underscores():
     form = "_ + 2*_"
@@ -25,8 +25,8 @@ def test_form_with_underscores():
     assert rdExp._2replaced == {'A', 'B'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()) == {'A', 'B'} 
-    assert set(rdExp._gene_2replaced.keys()) == {'A', 'B'} 
+    assert set(rdExp._gene_varia.keys()) == {'A', 'B'}
+    assert set(rdExp._gene_2replaced.keys()) == {'A', 'B'}
 
 def test_only_form_calc():
     form = "{a+b} + 2"
@@ -36,8 +36,8 @@ def test_only_form_calc():
     assert rdExp._2replaced == {'a+b'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()), {'a' == 'b'} 
-    assert set(rdExp._gene_2replaced.keys()) == {'a+b'} 
+    assert set(rdExp._gene_varia.keys()), {'a' == 'b'}
+    assert set(rdExp._gene_2replaced.keys()) == {'a+b'}
 
 def test_only_form_cond():
     form = "{a} + 2"
@@ -48,8 +48,8 @@ def test_only_form_cond():
     assert rdExp._2replaced == {'a'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()) == {'a'} 
-    assert set(rdExp._gene_2replaced.keys()) == {'a'} 
+    assert set(rdExp._gene_varia.keys()) == {'a'}
+    assert set(rdExp._gene_2replaced.keys()) == {'a'}
 
     assert rdExp._gene_varia['a'] == 3
 
@@ -62,8 +62,8 @@ def test_only_form_conds():
     assert rdExp._2replaced == {'a'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()) == {'a'} 
-    assert set(rdExp._gene_2replaced.keys()) == {'a'} 
+    assert set(rdExp._gene_varia.keys()) == {'a'}
+    assert set(rdExp._gene_2replaced.keys()) == {'a'}
 
     assert rdExp._gene_varia['a'] in list(range(5))
     assert rdExp._gene_varia['a'] % 2 == 1
@@ -77,8 +77,8 @@ def test_only_form_calc_cond():
     assert rdExp._2replaced, {'a', 'b' == 'a*3'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()), {'a' == 'b'} 
-    assert set(rdExp._gene_2replaced.keys()), {'a', 'b' == 'a*3'} 
+    assert set(rdExp._gene_varia.keys()), {'a' == 'b'}
+    assert set(rdExp._gene_2replaced.keys()), {'a', 'b' == 'a*3'}
 
     assert rdExp._gene_varia['a'] == 3
 
@@ -91,8 +91,8 @@ def test_only_form_calc_cond_calc():
     assert rdExp._2replaced, {'b', 'a*3' == 'a+b'}
 
     rdExp()
-    assert set(rdExp._gene_varia.keys()), {'a' == 'b'} 
-    assert set(rdExp._gene_2replaced.keys()), {'b', 'a*3' == 'a+b'} 
+    assert set(rdExp._gene_varia.keys()), {'a' == 'b'}
+    assert set(rdExp._gene_2replaced.keys()), {'b', 'a*3' == 'a+b'}
 
     assert (rdExp._gene_varia['a'] + rdExp._gene_varia['b']) == 3
 
@@ -101,5 +101,5 @@ def test_only_form_calc_cond_calc():
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/calculus/test/test_render.py b/pymath/calculus/test/test_render.py
index 8c38309..edd85d3 100644
--- a/pymath/calculus/test/test_render.py
+++ b/pymath/calculus/test/test_render.py
@@ -20,8 +20,8 @@ def mass_poly_test(operation, rg= 5):
     :rg: number of potential values for coefs
     :returns: @todo
     """
-    coefs_p = [[(i-2),(j-2)] for i,j in permutations(range(rg),2)] 
-    coefs_q = [[2*(i-2),2*(j-2)] for i,j in permutations(range(rg),2)] 
+    coefs_p = [[(i-2),(j-2)] for i,j in permutations(range(rg),2)]
+    coefs_q = [[2*(i-2),2*(j-2)] for i,j in permutations(range(rg),2)]
     l_p = [Polynom(i) for i in coefs_p]
     l_q = [Polynom(i) for i in coefs_q]
     return [Expression([l_p[i],l_q[j],op.get_op(operation)]) for i,j in permutations(range(len(coefs_p)),2)]
@@ -306,5 +306,5 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/calculus/test/test_str2tokens.py b/pymath/calculus/test/test_str2tokens.py
index 03eeb27..cb7de0c 100644
--- a/pymath/calculus/test/test_str2tokens.py
+++ b/pymath/calculus/test/test_str2tokens.py
@@ -13,20 +13,20 @@ class TestStr2tokens(unittest.TestCase):
     def test_str2intokens(self):
         ans = str2in_tokens("2+3*4")
         self.assertEqual(ans, [2, "+", 3, "*", 4])
-        
+
         ans = str2in_tokens("2*3+4")
         self.assertEqual(ans, [2, "*", 3, "+", 4])
-        
+
 
     def test_in2post_fix(self):
         in_tokens = str2in_tokens("2+3*4")
         ans = in2post_fix(in_tokens)
         self.assertEqual(ans, [2, 3, 4, "*", "+"])
-        
+
         in_tokens = str2in_tokens("2*3+4")
         ans = in2post_fix(in_tokens)
         self.assertEqual(ans, [2, 3,"*", 4, "+"])
-        
+
 
         # TODO: Ajouter des tests pour les cas particuliers... |sam. nov.  8 17:39:18 CET 2014
     def test_str2in_tokens_big_num(self):
@@ -82,5 +82,5 @@ if __name__ == '__main__':
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/stat/__init__.py b/pymath/stat/__init__.py
index f5b4d75..0e38917 100644
--- a/pymath/stat/__init__.py
+++ b/pymath/stat/__init__.py
@@ -7,4 +7,4 @@ from .weightedDataset import WeightedDataset
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
diff --git a/pymath/stat/dataset.py b/pymath/stat/dataset.py
index 51069ad..4d6b8f6 100644
--- a/pymath/stat/dataset.py
+++ b/pymath/stat/dataset.py
@@ -15,7 +15,7 @@ from .random_generator import random_generator
 
 class Dataset(list):
     """ A dataset (a list) with statistics and latex rendering methods
-    
+
     >>> s = Dataset(range(100))
     >>> s.sum()
     4950
@@ -52,11 +52,11 @@ class Dataset(list):
             exact_mean)
 
         return cls(data, data_name = data_name)
-    
+
     def __init__(self, data = [], data_name = "Valeurs"):
-        """ 
+        """
         Create a numeric data set
-        
+
         :param data: values of the data set
         :param data_name: name of the data set
         """
@@ -83,10 +83,10 @@ class Dataset(list):
     @number_factory
     def sum(self):
         return sum(self)
-    
+
     @number_factory
     def mean(self):
-        return self.sum()/self.effectif_total() 
+        return self.sum()/self.effectif_total()
 
     @number_factory
     def deviation(self):
@@ -97,7 +97,7 @@ class Dataset(list):
     @number_factory
     def variance(self):
         return self.deviation()/self.effectif_total()
-    
+
     @number_factory
     def sd(self):
         """ Compute the standard deviation """
@@ -150,18 +150,18 @@ class Dataset(list):
             return self[ceil(position)]
 
     def posi_quartile(self, quartile = 1):
-        """ 
+        """
         Calcul la position du quartile
 
         :param quartile: le quartile concerné
-        
+
         :return : la position du quartile (arondis à l'entier suppérieur, non arrondis)
         """
         return quartile * self.effectif_total() / 4
-    
+
     # --------------------------
     # Rendu latex
-    
+
     def tabular_latex(self, nbr_lines = 1):
         """ Latex code to display dataset as a tabular """
         d_per_line = self.effectif_total() // nbr_lines
@@ -188,5 +188,5 @@ class Dataset(list):
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/stat/number_tools.py b/pymath/stat/number_tools.py
index 04a597b..0a44c0b 100644
--- a/pymath/stat/number_tools.py
+++ b/pymath/stat/number_tools.py
@@ -23,5 +23,5 @@ def number_factory(fun):
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/stat/random_generator.py b/pymath/stat/random_generator.py
index 619dcef..fa17c3b 100644
--- a/pymath/stat/random_generator.py
+++ b/pymath/stat/random_generator.py
@@ -70,5 +70,5 @@ def random_generator(length,\
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del
 
diff --git a/pymath/stat/weightedDataset.py b/pymath/stat/weightedDataset.py
index 3ed3c73..60057d6 100644
--- a/pymath/stat/weightedDataset.py
+++ b/pymath/stat/weightedDataset.py
@@ -16,7 +16,7 @@ from .number_tools import number_factory
 
 class WeightedDataset(dict):
     """ A weighted dataset with statistics and latex rendering methods
-    
+
     >>> w = WeightedDataset([1, 2, 3, 4], "Enfants", [10, 11, 12, 13])
     >>> print(w)
     {1: 10, 2: 11, 3: 12, 4: 13}
@@ -32,12 +32,12 @@ class WeightedDataset(dict):
     1.24
     >>> w.sd()
     1.11
-    
+
     """
-    
+
     def __init__(self, datas = [], data_name = "Valeurs", weights = [], weight_name = "Effectifs"):
-        """ 
-        Initiate the WeightedDataset 
+        """
+        Initiate the WeightedDataset
         """
         if datas and not weights:
             weightedDatas = Counter(datas)
@@ -51,7 +51,7 @@ class WeightedDataset(dict):
 
         self.data_name = data_name
         self.weight_name = weight_name
-    
+
     def add_data(self, data, weight = 1):
         try:
             self[data] += weight
@@ -72,7 +72,7 @@ class WeightedDataset(dict):
 
     @number_factory
     def mean(self):
-        return self.sum()/self.effectif_total() 
+        return self.sum()/self.effectif_total()
 
     @number_factory
     def deviation(self):
@@ -83,7 +83,7 @@ class WeightedDataset(dict):
     @number_factory
     def variance(self):
         return self.deviation()/self.effectif_total()
-    
+
     @number_factory
     def sd(self):
         """ Compute the standard deviation """
@@ -141,19 +141,19 @@ class WeightedDataset(dict):
             return expanded_values[ceil(position)]
 
     def posi_quartile(self, quartile = 1):
-        """ 
+        """
         Calcul la position du quartile
 
         :param quartile: le quartile concerné
-        
+
         :return : la position du quartile (arondis à l'entier suppérieur, non arrondis)
         """
         return quartile * self.effectif_total() / 4
-    
-    
+
+
     # --------------------------
     # Rendu latex
-    
+
     def tabular_latex(self):
         """ Latex code to display dataset as a tabular """
         latex = "\\begin{{tabular}}{{|c|*{{{nbr_col}}}{{c|}}}} \n".format(nbr_col = len(self.keys()))
@@ -176,5 +176,5 @@ class WeightedDataset(dict):
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
-# cursor: 16 del 
+# cursor: 16 del