diff --git a/reviewstats/utils.py b/reviewstats/utils.py
index 7ad569a..c148cf0 100644
--- a/reviewstats/utils.py
+++ b/reviewstats/utils.py
@@ -1,4 +1,4 @@
-#
+## -*- coding: utf-8 -*-
 # Copyright (C) 2011 - Soren Hansen
 # Copyright (C) 2013 - Red Hat, Inc.
 #
@@ -14,6 +14,8 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations
 # under the License.
+"""Utility functions module
+"""
 
 import glob
 import json
@@ -30,6 +32,28 @@ LOG = logging.getLogger(__name__)
 
 
 def get_projects_info(project=None, all_projects=False, base_dir='./projects'):
+    """Return the list of project dict objects.
+
+    :param project: pathname of the JSON project info file.
+    :type project: str or None
+    :param bool all_projects:
+        If True deserialize all the “.json“ files of officials projects in
+        base_dir.
+    :param str base_dir:
+        dirname of the path containing the json projects files.
+    :return: unserialized json of project info.
+    :rtype: dict
+
+    project or all_projects=True must be given.
+
+    .. note::
+        Unofficial projects are filtered out if all_projects is True.
+        Official qualification is a key of the json file name “unofficial”, if
+        present and true, its an unofficial project.
+
+    .. note::
+        all_projects parameters overrides project parameter value if True
+    """
     if all_projects:
         files = glob.glob('%s/*.json' % base_dir)
     else:
@@ -52,6 +76,18 @@ def get_projects_info(project=None, all_projects=False, base_dir='./projects'):
 
 
 def projects_q(project):
+    """Return the gerrit query selecting all the project in the given list
+
+    :param project: List of gerrit project name.
+    :type project: list of str
+    :return:
+        gerrit query according to `Searching Changes`_ section of gerrit
+        documentation.
+    :rtype: str
+
+    .. _Searching Changes:
+        https://review.openstack.org/Documentation/user-search.html
+    """
     return ('(' +
             ' OR '.join(['project:' + p for p in project['subprojects']]) +
             ')')
@@ -59,6 +95,30 @@ def projects_q(project):
 
 def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
                 server='review.openstack.org'):
+    """Get the changesets data list.
+
+    :param projects: List of gerrit project names.
+    :type projects: list of str
+    :param str ssh_user: Gerrit username.
+    :param str ssh_key: Filename of one SSH key registered at gerrit.
+    :param bool only_open: If True, get only the not closed reviews.
+    :param str stable:
+        Name of the stable branch. If empty string, the changesets are not
+        filtered by any branch.
+
+    :return: List of de-serialized JSON changeset data as returned by gerrit.
+    :rtype: list
+
+    .. note::
+        If all the issue are requested whatever the branch is, a cache system
+        override the gerrit request.
+        Requesting only the open changes isn't nearly as big of a deal,
+        so just get the current data.
+        Also do not use cache for stable stats as they cover different
+        results.
+        Cached results are pickled per project in the following filenames:
+        “.{projectname}-changes.pickle”.
+    """
     all_changes = []
 
     client = paramiko.SSHClient()
@@ -71,10 +131,6 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
 
         if not only_open and not stable:
             # Only use the cache for *all* changes (the entire history).
-            # Requesting only the open changes isn't nearly as big of a deal,
-            # so just get the current data.
-            # Also do not use cache for stable stats as they cover different
-            # results.
             pickle_fn = '.%s-changes.pickle' % project['name']
 
             if os.path.isfile(pickle_fn):
@@ -132,6 +188,13 @@ def get_changes(projects, ssh_user, ssh_key, only_open=False, stable='',
 
 
 def patch_set_approved(patch_set):
+    """Return True if the patchset has been approved.
+
+    :param dict patch_set: De-serialized dict of a gerrit change
+
+    :return: True if one of the patchset reviews approved it.
+    :rtype: bool
+    """
     approvals = patch_set.get('approvals', [])
     for review in approvals:
         if review['type'] == 'APRV':
@@ -140,16 +203,24 @@ def patch_set_approved(patch_set):
 
 
 def get_age_of_patch(patch, now_ts):
+    """Compute the number of seconds since the patch submission and now.
+
+    :param dict patch: Deserialized JSON of a Gerrit patchset
+    :param int now_ts: Unix-like timestamp in seconds since EPOCH.
+    :return int: number of seconds between patch submission and now_ts
+
+    .. note::
+        The createdOn timestamp on the patch isn't what we want.
+        It's when the patch was written, not submitted for review.
+        The next best thing in the data we have is the time of the
+        first review.  When all is working well, jenkins or smokestack
+        will comment within the first hour or two, so that's better
+        than the other timestamp, which may reflect that the code
+        was written many weeks ago, even though it was just recently
+        submitted for review.
+    """
     approvals = patch.get('approvals', [])
     approvals.sort(key=lambda a: a['grantedOn'])
-    # The createdOn timestamp on the patch isn't what we want.
-    # It's when the patch was written, not submitted for review.
-    # The next best thing in the data we have is the time of the
-    # first review.  When all is working well, jenkins or smokestack
-    # will comment within the first hour or two, so that's better
-    # than the other timestamp, which may reflect that the code
-    # was written many weeks ago, even though it was just recently
-    # submitted for review.
     if approvals:
         return now_ts - approvals[0]['grantedOn']
     else: