From 7efe9612bcb903473c415a130c70a7990df47577 Mon Sep 17 00:00:00 2001
From: Fabian Joswig <fabian.joswig@ed.ac.uk>
Date: Thu, 21 Oct 2021 10:59:53 +0100
Subject: [PATCH] npr doc extended, CObs now have real and imag properties

---
 pyerrors/npr.py      | 20 ++++++++++++++------
 pyerrors/pyerrors.py | 14 +++++++++++---
 2 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/pyerrors/npr.py b/pyerrors/npr.py
index ad7d7de8..96e35514 100644
--- a/pyerrors/npr.py
+++ b/pyerrors/npr.py
@@ -38,7 +38,7 @@ class Npr_matrix(np.ndarray):
         if s_mom is not None and o_mom is not None:
             if not np.allclose(s_mom, o_mom):
                 raise Exception(name + ' does not match.')
-        return o_mom if o_mom else s_mom
+        return o_mom if o_mom is not None else s_mom
 
     def __matmul__(self, other):
         return self.__new__(Npr_matrix,
@@ -65,13 +65,23 @@ def _check_geometry():
             raise Exception("Temporal extent 'T' must be an integer.")
 
 
-def _invert_propagator(prop):
+def inv_propagator(prop):
+    """ Inverts a 12x12 quark propagator"""
+    if prop.shape != (12, 12):
+        raise Exception("Only 12x12 propagators can be inverted.")
     return Npr_matrix(mat_mat_op(anp.linalg.inv, prop), prop.mom_in)
 
 
-def Zq(prop, fermion='Wilson'):
+def Zq(inv_prop, fermion='Wilson'):
+    """ Calculates the quark field renormalization constant Zq
+
+        Attributes:
+        inv_prop -- Inverted 12x12 quark propagator
+        fermion -- Fermion type for which the tree-level propagator is used
+                   in the calculation of Zq. Default Wilson.
+    """
     _check_geometry()
-    mom = np.copy(prop.mom_in)
+    mom = np.copy(inv_prop.mom_in)
     mom[3] /= T / L
     sin_mom = np.sin(2 * np.pi / L * mom)
 
@@ -80,8 +90,6 @@ def Zq(prop, fermion='Wilson'):
     else:
         raise Exception("Fermion type '" + fermion + "' not implemented")
 
-    inv_prop = _invert_propagator(prop)
-
     res = 1 / 12. * np.trace(inv_prop @ np.kron(np.eye(3, dtype=int), p_slash))
     res.gamma_method()
 
diff --git a/pyerrors/pyerrors.py b/pyerrors/pyerrors.py
index acb704c2..853809c6 100644
--- a/pyerrors/pyerrors.py
+++ b/pyerrors/pyerrors.py
@@ -650,13 +650,21 @@ class Obs:
 
 class CObs:
     """Class for a complex valued observable."""
-    __slots__ = ['real', 'imag', 'tag']
+    __slots__ = ['_real', '_imag', 'tag']
 
     def __init__(self, real, imag=0.0):
-        self.real = real
-        self.imag = imag
+        self._real = real
+        self._imag = imag
         self.tag = None
 
+    @property
+    def real(self):
+        return self._real
+
+    @property
+    def imag(self):
+        return self._imag
+
     def gamma_method(self, **kwargs):
         if isinstance(self.real, Obs):
             self.real.gamma_method(**kwargs)