Warning instead of exception if matplotlib.use() is called too late.

efiring · efiring · commit 2aa668318549 · 2007-12-26T17:10:34.000Z
svn path=/trunk/matplotlib/; revision=4790
diff --git a/CHANGELOG b/CHANGELOG
@@ -1,3 +1,6 @@
+2007-12-26 Reduce too-late use of matplotlib.use() to a warning
+           instead of an exception, for backwards compatibility - EF
+
 2007-12-25 Fix bug in errorbar, identified by Noriko Minakawa - EF
 
 2007-12-25 Changed masked array importing to work with the upcoming
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -727,8 +727,11 @@ def rcdefaults():
     except:
         from config import rcParams, rcdefaults
 
-_use_error_msg = """ matplotlib.use() must be called *before* pylab
-or matplotlib.backends is imported for the first time."""
+_use_error_msg = """ This call to matplotlib.use() has no effect
+because the the backend has already been chosen;
+matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
+or matplotlib.backends is imported for the first time.
+"""
 
 def use(arg):
     """
@@ -747,7 +750,7 @@ def use(arg):
     be called before importing matplotlib.backends.
     """
     if 'matplotlib.backends' in sys.modules:
-        raise RuntimeError(_use_error_msg)
+        warnings.warn(_use_error_msg)
     be_parts = arg.split('.')
     name = validate_backend(be_parts[0])
     rcParams['backend'] = name
