Histograms.xml python script housekeeping

tools/metrics/histograms/histograms_path.py

Index: tools/metrics/histograms/histograms_path.py
diff --git a/tools/metrics/histograms/histograms_path.py b/tools/metrics/histograms/histograms_path.py
new file mode 100644
index 0000000000000000000000000000000000000000..e7c3bc3b6bda5ab7b43bfa9a14af36f40daf6b6a
--- /dev/null
+++ b/tools/metrics/histograms/histograms_path.py
@@ -0,0 +1,22 @@
+# Copyright 2013 The Chromium Authors. All rights reserved.

[Ilya Sherman, 2015/05/27 00:12:24]

nit: 2015

[ncarter (slow), 2015/05/29 23:01:10]

Done.

+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Utility functions for resolving file paths in histograms scripts."""
+
+import os.path
+
+
+def GetHistogramsFile():
+  """Returns the path to histograms.xml.
+
+  Prefer using this function instead of just open("histograms.xml"), so that
+  scripts work properly even if run from outside the histograms directory.
+  """
+  return os.path.join(os.path.dirname(__file__), 'histograms.xml')
+
+
+def GetInputFile(src_relative_file_path):

[Ilya Sherman, 2015/05/27 00:12:24]

Is it worth providing this at a higher level, so that the actions and rappor
scripts can also be cleaned up to use this?

[ncarter (slow), 2015/05/29 23:01:10]

I moved it to common (as path_util.py). I also added __init__.py files to both
common and histograms, so that the import statements give a little more of a
hint where these files are coming from.

+  """Converts a src/-relative file path into a path that can be opened."""
+  depth = [os.path.dirname(__file__), '..', '..', '..']
+  return os.path.join(*(depth + src_relative_file_path.split('/')))

[Ilya Sherman, 2015/05/27 00:12:24]

Out of curiousity, what does the "*" operator do?

[ncarter (slow), 2015/05/29 23:01:10]

https://docs.python.org/2/tutorial/controlflow.html#unpacking-argument-lists

Basically, the join() function accepts a variable number of positional
arguments, but here we have a list of strings to be joined. "*" lets you unpack
the list so that each list element is passed an argument.