[image_pipeline] style edits

* 80 characters line limit
* shortening some code
* removed dead code
* add doctest for _key_for_pipe function

docs/topics/media-pipeline.rst

@@ -191,10 +191,11 @@ For the Images Pipeline, set :setting:`IMAGES_URLS_FIELD` and/or
 If you need something more complex and want to override the custom pipeline
 behaviour, see :ref:`topics-media-pipeline-override`.
 
-If you have multiple image pipelines inheriting from ImagePipeline and you want to have different settings in different pipelines
-you can set setting keys preceded with uppercase name of your pipeline class. E.g. if your pipeline is called
-MyPipeline and you want to have custom IMAGES_URLS_FIELD you define setting MYPIPELINE_IMAGES_URLS_FIELD and your custom
-settings will be used.
+If you have multiple image pipelines inheriting from ImagePipeline and you want
+to have different settings in different pipelines you can set setting keys
+preceded with uppercase name of your pipeline class. E.g. if your pipeline is
+called MyPipeline and you want to have custom IMAGES_URLS_FIELD you define
+setting MYPIPELINE_IMAGES_URLS_FIELD and your custom settings will be used.
 
 
 Additional features
@@ -219,9 +220,9 @@ specifies the delay in number of days::
 
 The default value for both settings is 90 days.
 
-If you have pipeline that subclasses FilesPipeline and you'd like to have different setting
-for it you can set setting keys preceded by uppercase class name. E.g. given pipeline class
-called MyPipeline you can set setting key:
+If you have pipeline that subclasses FilesPipeline and you'd like to have
+different setting for it you can set setting keys preceded by uppercase
+class name. E.g. given pipeline class called MyPipeline you can set setting key:
 
     MYPIPELINE_FILES_EXPIRES = 180
 

scrapy/pipelines/files.py

@@ -3,7 +3,7 @@ Files Pipeline
 
 See documentation in topics/media-pipeline.rst
 """
-
+import functools
 import hashlib
 import os
 import os.path
@@ -232,18 +232,20 @@ class FilesPipeline(MediaPipeline):
 
         cls_name = "FilesPipeline"
         self.store = self._get_store(store_uri)
+        resolve = functools.partial(self._key_for_pipe,
+                                    base_class_name=cls_name)
         self.expires = settings.getint(
-            self._key_for_pipe('FILES_EXPIRES', cls_name), self.EXPIRES
+            resolve('FILES_EXPIRES'), self.EXPIRES
         )
         if not hasattr(self, "FILES_URLS_FIELD"):
             self.FILES_URLS_FIELD = self.DEFAULT_FILES_URLS_FIELD
         if not hasattr(self, "FILES_RESULT_FIELD"):
             self.FILES_RESULT_FIELD = self.DEFAULT_FILES_RESULT_FIELD
         self.files_urls_field = settings.get(
-            self._key_for_pipe('FILES_URLS_FIELD', cls_name), self.FILES_URLS_FIELD
+            resolve('FILES_URLS_FIELD'), self.FILES_URLS_FIELD
         )
         self.files_result_field = settings.get(
-            self._key_for_pipe('FILES_RESULT_FIELD', cls_name), self.FILES_RESULT_FIELD
+            resolve('FILES_RESULT_FIELD'), self.FILES_RESULT_FIELD
         )
 
         super(FilesPipeline, self).__init__(download_func=download_func)

scrapy/pipelines/images.py

@@ -3,7 +3,7 @@ Images Pipeline
 
 See documentation in topics/media-pipeline.rst
 """
-
+import functools
 import hashlib
 import six
 
@@ -62,22 +62,24 @@ class ImagesPipeline(FilesPipeline):
         if not hasattr(self, "IMAGES_URLS_FIELD"):
             self.IMAGES_URLS_FIELD = self.DEFAULT_IMAGES_URLS_FIELD
 
-        default_images_urls_field = getattr(self, "IMAGES_URLS_FIELD", "DEFAULT_IMAGES_URLS_FIELD")
+        resolve = functools.partial(self._key_for_pipe, base_class_name=cls_name)
+
         self.images_urls_field = settings.get(
-            self._key_for_pipe('IMAGES_URLS_FIELD', cls_name), default_images_urls_field
+            resolve('IMAGES_URLS_FIELD'),
+            self.IMAGES_URLS_FIELD
         )
-        default_images_result_field = getattr(self, "IMAGES_RESULT_FIELD", "DEFAULT_IMAGES_RESULT_FIELD")
         self.images_result_field = settings.get(
-            self._key_for_pipe('IMAGES_RESULT_FIELD', cls_name), default_images_result_field
+            resolve('IMAGES_RESULT_FIELD'),
+            self.IMAGES_RESULT_FIELD
         )
         self.min_width = settings.getint(
-            self._key_for_pipe('IMAGES_MIN_WIDTH', cls_name), self.MIN_WIDTH
+            resolve('IMAGES_MIN_WIDTH'), self.MIN_WIDTH
         )
         self.min_height = settings.getint(
-            self._key_for_pipe('IMAGES_MIN_HEIGHT', cls_name), self.MIN_HEIGHT
+            resolve('IMAGES_MIN_HEIGHT'), self.MIN_HEIGHT
         )
         self.thumbs = settings.get(
-            self._key_for_pipe('IMAGES_THUMBS', cls_name), self.THUMBS
+            resolve('IMAGES_THUMBS'), self.THUMBS
         )
 
     @classmethod

scrapy/pipelines/media.py

@@ -28,18 +28,17 @@ class MediaPipeline(object):
         self.download_func = download_func
 
 
-    def _key_for_pipe(self, key, base_class_name):
+    def _key_for_pipe(self, key, base_class_name=None):
         """
-        Allow setting settings for user defined MediaPipelines that inherit from base.
-
-        User can define setting key:
-
-        MYPIPELINENAME_IMAGE_SETTING_NAME = <some value>
-
-        and it will override default settings and class attributes.
+        >>> result = MediaPipeline()._key_for_pipe("IMAGES")
+        >>> assert result == "IMAGES"
+        >>> class MyPipe(MediaPipeline):
+        ...     pass
+        >>> other_key = MyPipe()._key_for_pipe("IMAGES", base_class_name="MediaPipeline")
+        >>> assert other_key == "MYPIPE_IMAGES"
         """
         class_name = self.__class__.__name__
-        if class_name == base_class_name:
+        if class_name == base_class_name or not base_class_name:
             return key
         return "{}_{}".format(class_name.upper(), key)