diff --git a/random_expression.py b/random_expression.py
new file mode 100644
index 0000000..ceed4ac
--- /dev/null
+++ b/random_expression.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python
+# encoding: utf-8
+
+from random import randint
+import re
+
+class RdExpression(object):
+    """A generator of random expression builder"""
+
+    def __init__(self, form, conditions = []):
+        """Initiate the generator
+
+        :param form: the form of the expression (/!\ variables need to be in brackets {})
+        :param conditions: condition on variables (/!\ variables need to be in brackets {})
+
+        """
+        self._form = form
+        self._conditions = conditions
+        self._letters = self.get_letters()
+        self._gene_varia = {}
+        
+    def get_letters(self):
+        """Find letters in the form
+        :returns: list of letters
+
+        """
+        pattern = "\{(\w+)\}"
+        varia = re.findall(pattern, self._form)
+        print(varia)
+        return list(set(varia))
+
+    def __call__(self, val_min = -10, val_max = 10):
+        """RdExpression once it is initiate act like a function which create random expressions.
+
+        :param val_min: minimum value random generation
+        :param val_max: maximum value random generation
+        :returns: an random expression
+
+        """
+        self.gene_varia(val_min, val_max)
+
+        while not(self.val_conditions()):
+            self.gene_varia(val_min, val_max)
+
+        return self._form.format(**self._gene_varia)
+
+    def gene_varia(self, val_min = -10, val_max = 10):
+        """RAndomly generates variables/letters
+
+        """
+        for l in self._letters:
+            self._gene_varia[l] = randint(val_min, val_max)
+
+    def val_conditions(self):
+        """Tells whether or not conditions are validates
+        :returns: boolean
+
+        """
+        return eval(" and ".join(self._conditions).format(**self._gene_varia))
+
+
+if __name__ == '__main__':
+    form = "{a}x + 2*{b}"
+    cond = ["{a} + {b} in [1, 2, 3, 4, 5]"]
+    rdExp1 = RdExpression(form, cond)
+    print(rdExp1())
+
+
+
+
+
+# -----------------------------
+# Reglages pour 'vim'
+# vim:set autoindent expandtab tabstop=4 shiftwidth=4:
+# cursor: 16 del