Implemented PAdic.as_tuple_from_zero, following suggestion. It raises…

… ValueError if not a p-adic integer (negative valuation).

pyadic/padic.py

@@ -173,8 +173,16 @@ def k(self, value):
 
     @property
     def as_tuple(self):
+        """Tuple reprensentation of the mantissa."""
         return (to_base(int(self), self.p) + tuple([0 for i in range(self.k)]))[:self.k]
 
+    @property
+    def as_tuple_from_zero(self):
+        """Tuple representation of the mantissa, shifted to start from p^0 term."""
+        if self.n < 0:
+            raise ValueError("PAdic tuple from zero representation is only defined for PAdic integers (non-negative valuation).")
+        return (0, ) * self.n + self.as_tuple
+
     def __getstate__(self):
         return (int(self), self.p, self.k, self.n)
 

tests/test_finite_field.py

@@ -30,8 +30,10 @@ def test_same_class_instantiation_and_unary_plus():
 def test_instantiation_from_padic():
     assert ModP(PAdic(123, 2 ** 31 - 19, 3)) == ModP(123, (2 ** 31 - 19) ** 3)
 
+
 def test_instantiation_from_string():
-    assert ModP('+123', 2 ** 31 - 1) == ModP('-2147483524', 2 ** 31 - 1) ==  ModP(123, 2 ** 31 - 1)
+    assert ModP('+123', 2 ** 31 - 1) == ModP('-2147483524', 2 ** 31 - 1) == ModP(123, 2 ** 31 - 1)
+
 
 def test_instantiation_with_complex():
     p = 2 ** 31 - 19

tests/test_padic.py

@@ -43,6 +43,14 @@ def test_str_non_zero():
     assert str(PAdic(1 + 2 * p + 3 * p ** 2, p, k)) == "1 + 2*{p} + 3*{p}^2 + O({p}^{k})".format(p=p, k=k)
 
 
+def test_tuple_from_zero_representation():
+    a = PAdic(64, 2, 12)
+    assert a.as_tuple_from_zero == (0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, )
+    a = PAdic(Q(1, 2), 2, 12)
+    with pytest.raises(ValueError):
+        a.as_tuple_from_zero
+
+
 def test_isscalar():
     assert numpy.isscalar(PAdic(3, 7, 1))