Isolated matplotlib.pyplot dependencies; fixes #690

librosa/display.py

@@ -20,7 +20,8 @@
 import warnings
 
 import numpy as np
-import matplotlib.pyplot as plt
+from matplotlib.cm import get_cmap
+from matplotlib.axes import Axes
 from matplotlib.ticker import Formatter, ScalarFormatter
 from matplotlib.ticker import LogLocator, FixedLocator, MaxNLocator
 from matplotlib.ticker import SymmetricalLogLocator
@@ -303,7 +304,7 @@ def cmap(data, robust=True, cmap_seq='magma', cmap_bool='gray_r', cmap_div='cool
     data = np.atleast_1d(data)
 
     if data.dtype == 'bool':
-        return plt.get_cmap(cmap_bool)
+        return get_cmap(cmap_bool)
 
     data = data[np.isfinite(data)]
 
@@ -316,9 +317,9 @@ def cmap(data, robust=True, cmap_seq='magma', cmap_bool='gray_r', cmap_div='cool
     min_val = np.percentile(data, min_p)
 
     if min_val >= 0 or max_val <= 0:
-        return plt.get_cmap(cmap_seq)
+        return get_cmap(cmap_seq)
 
-    return plt.get_cmap(cmap_div)
+    return get_cmap(cmap_div)
 
 
 def __envelope(x, hop):
@@ -683,8 +684,7 @@ def specshow(data, x_coords=None, y_coords=None,
 
     axes = __check_axes(ax)
     out = axes.pcolormesh(x_coords, y_coords, data, **kwargs)
-    if ax is None:
-        plt.sci(out)
+    __set_current_image(ax, out)
 
     axes.set_xlim(x_coords.min(), x_coords.max())
     axes.set_ylim(y_coords.min(), y_coords.max())
@@ -700,6 +700,18 @@ def specshow(data, x_coords=None, y_coords=None,
     return axes
 
 
+def __set_current_image(ax, img):
+    '''Helper to set the current image in pyplot mode.
+
+    If the provided `ax` is not `None`, then we assume that the user is using the object API.
+    In this case, the pyplot current image is not set.
+    '''
+
+    if ax is None:
+        import matplotlib.pyplot as plt
+        plt.sci(img)
+
+
 def __mesh_coords(ax_type, coords, n, **kwargs):
     '''Compute axis coordinates'''
 
@@ -734,10 +746,11 @@ def __mesh_coords(ax_type, coords, n, **kwargs):
 def __check_axes(axes):
     '''Check if "axes" is an instance of an axis object. If not, use `gca`.'''
     if axes is None:
+        import matplotlib.pyplot as plt
         axes = plt.gca()
-    if not isinstance(axes, plt.Axes):
-        raise ValueError("`axes` must be an instance of plt.Axes. "
-                         "Found type {}".format(type(axes)))
+    elif not isinstance(axes, Axes):
+        raise ValueError("`axes` must be an instance of matplotlib.axes.Axes. "
+                         "Found type(axes)={}".format(type(axes)))
     return axes