logger creation removed from __init__.py

Fixes danijar#11

handout/__init__.py

@@ -1,13 +1 @@
-import sys
-import logging
-
 from .handout import Handout
-
-
-# Set up logger.
-logger = logging.getLogger('handout')
-logger.setLevel(logging.INFO)
-logger.propagate = False  # Global logger should not print messages again.
-handler = logging.StreamHandler(sys.stdout)
-handler.setFormatter(logging.Formatter('%(message)s'))
-logger.addHandler(handler)

handout/handout.py

@@ -6,6 +6,7 @@
 import shutil
 
 from handout import blocks
+from handout import tools
 
 
 class Handout(object):
@@ -16,7 +17,7 @@ def __init__(self, directory, title='Handout'):
     self._title = title
     self._blocks = collections.defaultdict(list)
     self._pending = []
-    self._logger = logging.getLogger('handout')
+    self._logger = tools.get_logger()
     for info in inspect.stack():
       if info.filename == __file__:
         continue

handout/tests/test_tools.py

@@ -0,0 +1,7 @@
+import handout
+
+def test_get_logger_has_single_handler(): 
+    import handout # Simulate multiple imports of a package.
+    import handout
+    logger = handout.tools.get_logger()
+    assert len(logger.handlers) == 1 

handout/tools.py

@@ -1,3 +1,6 @@
+import sys
+import logging
+
 def strip_empty_lines(lines):
   output = []
   for line in lines:
@@ -12,3 +15,17 @@ def strip_empty_lines(lines):
     output.append(line)
   lines = reversed(output)
   return list(lines)
+
+
+def get_logger():
+  logger = logging.getLogger('handout')
+  logger.setLevel(logging.INFO) # A user can change this level later.
+  logger.propagate = False  # Global logger should not print messages again.
+  if not logger.handlers: # Prevents creation of multiple handlers.
+      handler = logging.StreamHandler(sys.stdout)
+      handler.setFormatter(logging.Formatter('%(message)s'))
+      logger.addHandler(handler)
+  # The logger can be accessed anywhere in code by its name with 
+  # `logging.getLogger('handout')`. However, we retrun the logger 
+  # explcitly here as function result, for convenience of use.
+  return logger