diff --git a/python/damask/Lambert.py b/python/damask/_Lambert.py
similarity index 98%
rename from python/damask/Lambert.py
rename to python/damask/_Lambert.py
index 0ff177f9b..b3f159ff6 100644
--- a/python/damask/Lambert.py
+++ b/python/damask/_Lambert.py
@@ -36,7 +36,7 @@ sc   = np.pi**(1./6.)/6.**(1./6.)
 beta = np.pi**(5./6.)/6.**(1./6.)/2.
 R1   = (3.*np.pi/4.)**(1./3.)
 
-def CubeToBall(cube):
+def cube_to_ball(cube):
     """
     Map a point in a uniform refinable cubical grid to a point on a uniform refinable grid on a ball.
 
@@ -59,7 +59,7 @@ def CubeToBall(cube):
         ball = np.zeros(3)
     else:
         # get pyramide and scale by grid parameter ratio
-        p = get_order(cube)
+        p = _get_order(cube)
         XYZ = cube[p] * sc
 
         # intercept all the points along the z-axis
@@ -87,7 +87,7 @@ def CubeToBall(cube):
     return ball
 
 
-def BallToCube(ball):
+def ball_to_cube(ball):
     """
     Map a point on a uniform refinable grid on a ball to a point in a uniform refinable cubical grid.
 
@@ -109,7 +109,7 @@ def BallToCube(ball):
     if np.allclose(ball,0.0,rtol=0.0,atol=1.0e-300):
         cube = np.zeros(3)
     else:
-        p = get_order(ball)
+        p = _get_order(ball)
         xyz3 = ball[p]
 
         # inverse M_3
@@ -137,7 +137,7 @@ def BallToCube(ball):
     return cube
 
 
-def get_order(xyz):
+def _get_order(xyz):
     """
     Get order of the coordinates.
 
diff --git a/python/damask/__init__.py b/python/damask/__init__.py
index 86f8d4862..7933651da 100644
--- a/python/damask/__init__.py
+++ b/python/damask/__init__.py
@@ -7,19 +7,19 @@ with open(_os.path.join(_os.path.dirname(__file__),'VERSION')) as _f:
     version = _re.sub(r'^v','',_f.readline().strip())
 
 # classes
-from .environment import Environment      # noqa
-from .table       import Table            # noqa
-from .ktv         import VTK              # noqa
-from .colormaps   import Colormap, Color  # noqa
-from .rotation    import Rotation         # noqa
-from .lattice     import Symmetry, Lattice# noqa
-from .orientation import Orientation      # noqa
-from .result      import Result           # noqa
-from .geom        import Geom             # noqa
-from .solver      import Solver           # noqa
+from ._environment import Environment      # noqa
+from ._table       import Table            # noqa
+from ._vtk         import VTK              # noqa
+from ._colormaps   import Colormap, Color  # noqa
+from ._rotation    import Rotation         # noqa
+from ._lattice     import Symmetry, Lattice# noqa
+from ._orientation import Orientation      # noqa
+from ._result      import Result           # noqa
+from ._geom        import Geom             # noqa
+from ._solver      import Solver           # noqa
 
 # deprecated
-from .asciitable  import ASCIItable       # noqa
+from ._asciitable import ASCIItable       # noqa
+from ._config     import Material         # noqa
+from ._test       import Test             # noqa
 from .util        import extendableOption # noqa
-from .config      import Material         # noqa
-from .test        import Test             # noqa
diff --git a/python/damask/asciitable.py b/python/damask/_asciitable.py
similarity index 100%
rename from python/damask/asciitable.py
rename to python/damask/_asciitable.py
diff --git a/python/damask/colormaps.py b/python/damask/_colormaps.py
similarity index 100%
rename from python/damask/colormaps.py
rename to python/damask/_colormaps.py
diff --git a/python/damask/config/__init__.py b/python/damask/_config/__init__.py
similarity index 100%
rename from python/damask/config/__init__.py
rename to python/damask/_config/__init__.py
diff --git a/python/damask/config/material.py b/python/damask/_config/material.py
similarity index 100%
rename from python/damask/config/material.py
rename to python/damask/_config/material.py
diff --git a/python/damask/environment.py b/python/damask/_environment.py
similarity index 100%
rename from python/damask/environment.py
rename to python/damask/_environment.py
diff --git a/python/damask/geom.py b/python/damask/_geom.py
similarity index 100%
rename from python/damask/geom.py
rename to python/damask/_geom.py
diff --git a/python/damask/lattice.py b/python/damask/_lattice.py
similarity index 99%
rename from python/damask/lattice.py
rename to python/damask/_lattice.py
index 3c949b02c..42aa0e9bd 100644
--- a/python/damask/lattice.py
+++ b/python/damask/_lattice.py
@@ -1,10 +1,8 @@
 import numpy as np
 
-from .rotation import Rotation
+from . import Rotation
 
-P = -1
 
-# ******************************************************************************************
 class Symmetry:
     """
     Symmetry operations for lattice systems.
diff --git a/python/damask/orientation.py b/python/damask/_orientation.py
similarity index 99%
rename from python/damask/orientation.py
rename to python/damask/_orientation.py
index d3f42c8d1..6cbe4f7d4 100644
--- a/python/damask/orientation.py
+++ b/python/damask/_orientation.py
@@ -1,7 +1,7 @@
 import numpy as np
 
-from .lattice  import Lattice
-from .rotation import Rotation
+from . import Lattice
+from . import Rotation
 
 class Orientation:
   """
diff --git a/python/damask/result.py b/python/damask/_result.py
similarity index 100%
rename from python/damask/result.py
rename to python/damask/_result.py
diff --git a/python/damask/rotation.py b/python/damask/_rotation.py
similarity index 99%
rename from python/damask/rotation.py
rename to python/damask/_rotation.py
index 28f55853b..0b481e149 100644
--- a/python/damask/rotation.py
+++ b/python/damask/_rotation.py
@@ -1,6 +1,6 @@
 import numpy as np
 
-from . import Lambert
+from ._Lambert import ball_to_cube, cube_to_ball
 
 P = -1
 
@@ -802,7 +802,7 @@ class Rotation:
     @staticmethod
     def ho2cu(ho):
         """Homochoric vector to cubochoric vector."""
-        return Lambert.BallToCube(ho)
+        return ball_to_cube(ho)
 
 
     #---------- Cubochoric ----------
@@ -834,4 +834,4 @@ class Rotation:
     @staticmethod
     def cu2ho(cu):
         """Cubochoric vector to homochoric vector."""
-        return Lambert.CubeToBall(cu)
+        return cube_to_ball(cu)
diff --git a/python/damask/solver/__init__.py b/python/damask/_solver/__init__.py
similarity index 100%
rename from python/damask/solver/__init__.py
rename to python/damask/_solver/__init__.py
diff --git a/python/damask/solver/marc.py b/python/damask/_solver/marc.py
similarity index 100%
rename from python/damask/solver/marc.py
rename to python/damask/_solver/marc.py
diff --git a/python/damask/solver/solver.py b/python/damask/_solver/solver.py
similarity index 100%
rename from python/damask/solver/solver.py
rename to python/damask/_solver/solver.py
diff --git a/python/damask/table.py b/python/damask/_table.py
similarity index 100%
rename from python/damask/table.py
rename to python/damask/_table.py
diff --git a/python/damask/test.py b/python/damask/_test.py
similarity index 100%
rename from python/damask/test.py
rename to python/damask/_test.py
diff --git a/python/damask/ktv.py b/python/damask/_vtk.py
similarity index 100%
rename from python/damask/ktv.py
rename to python/damask/_vtk.py
diff --git a/python/damask/mechanics.py b/python/damask/mechanics.py
index 63927e05d..674ff9c5a 100644
--- a/python/damask/mechanics.py
+++ b/python/damask/mechanics.py
@@ -85,7 +85,7 @@ def left_stretch(T):
         Tensor of which the left stretch is computed.
 
     """
-    return __polar_decomposition(T,'V')[0]
+    return _polar_decomposition(T,'V')[0]
 
 
 def maximum_shear(T_sym):
@@ -113,7 +113,7 @@ def Mises_strain(epsilon):
         Symmetric strain tensor of which the von Mises equivalent is computed.
 
     """
-    return __Mises(epsilon,2.0/3.0)
+    return _Mises(epsilon,2.0/3.0)
 
 
 def Mises_stress(sigma):
@@ -126,7 +126,7 @@ def Mises_stress(sigma):
         Symmetric stress tensor of which the von Mises equivalent is computed.
 
     """
-    return __Mises(sigma,3.0/2.0)
+    return _Mises(sigma,3.0/2.0)
 
 
 def PK2(P,F):
@@ -158,7 +158,7 @@ def right_stretch(T):
         Tensor of which the right stretch is computed.
 
     """
-    return __polar_decomposition(T,'U')[0]
+    return _polar_decomposition(T,'U')[0]
 
 
 def rotational_part(T):
@@ -171,7 +171,7 @@ def rotational_part(T):
         Tensor of which the rotational part is computed.
 
     """
-    return __polar_decomposition(T,'R')[0]
+    return _polar_decomposition(T,'R')[0]
 
 
 def spherical_part(T,tensor=False):
@@ -262,7 +262,7 @@ def transpose(T):
            np.transpose(T,(0,2,1))
 
 
-def __polar_decomposition(T,requested):
+def _polar_decomposition(T,requested):
     """
     Singular value decomposition.
 
@@ -290,7 +290,7 @@ def __polar_decomposition(T,requested):
     return tuple(output)
 
 
-def __Mises(T_sym,s):
+def _Mises(T_sym,s):
     """
     Base equation for Mises equivalent of a stres or strain tensor.