avocado.utils: Add output module

Add avocado.utils.output, a library with utility functions
for user friendly display of information.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/utils/output.py

+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+#
+# See LICENSE for more details.
+#
+# This code was inspired in the autotest project,
+#
+# client/shared/utils.py
+# Original author: Cleber Rosa <crosa@redhat.com>
+#
+# Copyright: Red Hat Inc. 2015
+# Author: Lucas Meneghel Rodrigues <lmr@redhat.com>
+
+"""
+Utility functions for user friendly display of information.
+"""
+
+import sys
+
+
+def display_data_size(size):
+    """
+    Display data size in human readable units (SI).
+
+    :param size: Data size, in Bytes.
+    :type size: int
+    :return: Human readable string with data size, using SI prefixes.
+    """
+    prefixes = ['B', 'KB', 'MB', 'GB', 'TB', 'PB']
+    factor = float(1000)
+    i = 0
+    while size >= factor:
+        if i >= len(prefixes) - 1:
+            break
+        size /= factor
+        i += 1
+
+    return '%.2f %s' % (size, prefixes[i])
+
+
+class ProgressBar(object):
+
+    """
+    Displays interactively the progress of a given task
+
+    Inspired/adapted from https://gist.github.com/t0xicCode/3306295
+    """
+
+    def __init__(self, minimum=0, maximum=100, width=75, title=''):
+        """
+        Initializes a new progress bar
+
+        :type minimum: integer
+        :param minimum: minimum (initial) value on the progress bar
+        :type maximum: integer
+        :param maximum: maximum (final) value on the progress bar
+        :type width: integer
+        :param with: number of columns, that is screen width
+        """
+        assert maximum > minimum
+
+        self.prog_bar = ''
+        self.old_prog_bar = ''
+
+        if title:
+            width -= len(title)
+
+        self.minimum = minimum
+        self.maximum = maximum
+        self.range = maximum - minimum
+        self.width = width
+        self.title = title
+
+        self.current_amount = minimum
+        self.update_amount(minimum)
+
+    def append_amount(self, amount):
+        """
+        Increments the current amount value.
+        """
+        self.update_amount(self.current_amount + amount)
+
+    def update_percentage(self, percentage):
+        """
+        Updates the progress bar to the new percentage.
+        """
+        self.update_amount((percentage * float(self.maximum)) / 100.0)
+
+    def update_amount(self, amount):
+        """
+        Performs sanity checks and update the current amount.
+        """
+        if amount < self.minimum:
+            amount = self.minimum
+        if amount > self.maximum:
+            amount = self.maximum
+        self.current_amount = amount
+
+        self._update_progress_bar()
+        self.draw()
+
+    def _update_progress_bar(self):
+        """
+        Builds the actual progress bar text.
+        """
+        diff = float(self.current_amount - self.minimum)
+        done = (diff / float(self.range)) * 100.0
+        done = int(round(done))
+
+        all_full = self.width - 2
+        hashes = (done / 100.0) * all_full
+        hashes = int(round(hashes))
+
+        if hashes == 0:
+            screen_text = "[>%s]" % (' '*(all_full-1))
+        elif hashes == all_full:
+            screen_text = "[%s]" % ('='*all_full)
+        else:
+            screen_text = "[%s>%s]" % ('='*(hashes-1), ' '*(all_full-hashes))
+
+        percent_string = str(done) + "%"
+
+        # slice the percentage into the bar
+        screen_text = ' '.join([screen_text, percent_string])
+
+        if self.title:
+            screen_text = '%s: %s' % (self.title,
+                                      screen_text)
+        self.prog_bar = screen_text
+
+    def draw(self):
+        """
+        Prints the updated text to the screen.
+        """
+        if self.prog_bar != self.old_prog_bar:
+            self.old_prog_bar = self.prog_bar
+            sys.stdout.write('\r' + self.prog_bar)
+            sys.stdout.flush()
+
+    def __str__(self):
+        """
+        Returns the current progress bar.
+        """
+        return str(self.prog_bar)

selftests/all/unit/avocado/utils_output_unittest.py

+import unittest
+import os
+import sys
+
+# simple magic for using scripts within a source tree
+basedir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+basedir = os.path.dirname(basedir)
+if os.path.isdir(os.path.join(basedir, 'avocado')):
+    sys.path.append(basedir)
+
+from avocado.utils import output
+
+
+class UtilsOutputTest(unittest.TestCase):
+
+    def testDisplayDataSizeFactor1024(self):
+        self.assertEqual(output.display_data_size(103), '103.00 B')
+        self.assertEqual(output.display_data_size(1024**1), '1.02 KB')
+        self.assertEqual(output.display_data_size(1024**2), '1.05 MB')
+        self.assertEqual(output.display_data_size(1024**3), '1.07 GB')
+        self.assertEqual(output.display_data_size(1024**4), '1.10 TB')
+        self.assertEqual(output.display_data_size(1024**5), '1.13 PB')
+        self.assertEqual(output.display_data_size(1024**6), '1152.92 PB')
+
+    def testDisplayDataSizeFactor1000(self):
+        self.assertEqual(output.display_data_size(1000**1), '1.00 KB')
+        self.assertEqual(output.display_data_size(1000**2), '1.00 MB')
+        self.assertEqual(output.display_data_size(1000**3), '1.00 GB')
+        self.assertEqual(output.display_data_size(1000**4), '1.00 TB')
+        self.assertEqual(output.display_data_size(1000**5), '1.00 PB')
+        self.assertEqual(output.display_data_size(1000**6), '1000.00 PB')
+
+
+if __name__ == '__main__':
+    unittest.main()