Move lazyprop decorator to the utils module

Author: scriptator

madmom/audio/cepstrogram.py

@@ -19,6 +19,7 @@
 from .filters import MelFilterbank
 from .spectrogram import Spectrogram
 from ..processors import Processor
+from ..utils import lazyprop
 
 
 class Cepstrogram(np.ndarray):
@@ -37,7 +38,6 @@ class applies some transformation (usually a DCT) on a spectrogram.
         one is instantiated with these additional keyword arguments.
 
     """
-
     # pylint: disable=super-on-old-class
     # pylint: disable=super-init-not-called
     # pylint: disable=attribute-defined-outside-init
@@ -130,19 +130,6 @@ def process(self, data, **kwargs):
 MFCC_DELTADELTA_FILTER = np.linspace(1, -1, 3) / 2
 
 
-# https://stackoverflow.com/questions/3012421/python-memoising-deferred-lookup-property-decorator#3013910
-def lazyprop(fn):
-    attr_name = '_lazy_' + fn.__name__
-
-    @property
-    def _lazyprop(self):
-        if not hasattr(self, attr_name):
-            setattr(self, attr_name, fn(self))
-        return getattr(self, attr_name)
-
-    return _lazyprop
-
-
 class MFCC(Cepstrogram):
     """
     MFCC class.

madmom/utils/__init__.py

@@ -591,6 +591,35 @@ def segment_axis(signal, frame_size, hop_size, axis=None, end='cut',
                                   dtype=signal.dtype)
 
 
+# taken from: https://stackoverflow.com/questions/3012421/
+def lazyprop(fn):
+    """
+    A decorator for a caching, lazily evaluated property. If a function is
+    decorated with @lazyprop, the original function of the resulting property
+    is only called on the first access. Afterwards the result which was
+    produced then is returned again.
+
+    Parameters
+    ----------
+    fn: Function
+        A function without argument which returns the value of the property
+
+    Returns
+    -------
+    property
+        A property which wraps the original one and caches it first result
+    """
+    attr_name = '_lazy_' + fn.__name__
+
+    @property
+    def _lazyprop(self):
+        if not hasattr(self, attr_name):
+            setattr(self, attr_name, fn(self))
+        return getattr(self, attr_name)
+
+    return _lazyprop
+
+
 # keep namespace clean
 del contextlib