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117 lines
4.0 KiB
117 lines
4.0 KiB
# Copyright (c) 2013 The Chromium OS Authors. All rights reserved. |
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# Use of this source code is governed by a BSD-style license that can be |
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# found in the LICENSE file. |
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"""Histogram generation tools.""" |
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from collections import defaultdict |
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import format_utils |
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class Histogram(object): |
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"""A histogram generating object. |
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This object serves the sole purpose of formatting (key, val) pairs as an |
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ASCII histogram, including bars and percentage markers, and taking care of |
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label alignment, scaling, etc. In addition to the standard __init__ |
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interface, two static methods are provided for conveniently converting data |
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in different formats into a histogram. Histogram generation is exported via |
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its __str__ method, and looks as follows: |
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Yes |################ | 5 (83.3%) |
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No |### | 1 (16.6%) |
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TODO(garnold) we may want to add actual methods for adding data or tweaking |
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the output layout and formatting. For now, though, this is fine. |
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""" |
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def __init__(self, data, scale=20, formatter=None): |
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"""Initialize a histogram object. |
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Args: |
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data: list of (key, count) pairs constituting the histogram |
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scale: number of characters used to indicate 100% |
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formatter: function used for formatting raw histogram values |
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""" |
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self.data = data |
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self.scale = scale |
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self.formatter = formatter or str |
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self.max_key_len = max([len(str(key)) for key, count in self.data]) |
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self.total = sum([count for key, count in self.data]) |
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@staticmethod |
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def FromCountDict(count_dict, scale=20, formatter=None, key_names=None): |
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"""Takes a dictionary of counts and returns a histogram object. |
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This simply converts a mapping from names to counts into a list of (key, |
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count) pairs, optionally translating keys into name strings, then |
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generating and returning a histogram for them. This is a useful convenience |
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call for clients that update a dictionary of counters as they (say) scan a |
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data stream. |
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Args: |
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count_dict: dictionary mapping keys to occurrence counts |
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scale: number of characters used to indicate 100% |
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formatter: function used for formatting raw histogram values |
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key_names: dictionary mapping keys to name strings |
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Returns: |
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A histogram object based on the given data. |
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""" |
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namer = None |
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if key_names: |
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namer = lambda key: key_names[key] |
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else: |
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namer = lambda key: key |
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hist = [(namer(key), count) for key, count in count_dict.items()] |
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return Histogram(hist, scale, formatter) |
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@staticmethod |
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def FromKeyList(key_list, scale=20, formatter=None, key_names=None): |
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"""Takes a list of (possibly recurring) keys and returns a histogram object. |
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This converts the list into a dictionary of counters, then uses |
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FromCountDict() to generate the actual histogram. For example: |
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['a', 'a', 'b', 'a', 'b'] --> {'a': 3, 'b': 2} --> ... |
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Args: |
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key_list: list of (possibly recurring) keys |
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scale: number of characters used to indicate 100% |
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formatter: function used for formatting raw histogram values |
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key_names: dictionary mapping keys to name strings |
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Returns: |
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A histogram object based on the given data. |
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""" |
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count_dict = defaultdict(int) # Unset items default to zero |
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for key in key_list: |
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count_dict[key] += 1 |
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return Histogram.FromCountDict(count_dict, scale, formatter, key_names) |
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def __str__(self): |
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hist_lines = [] |
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hist_bar = '|' |
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for key, count in self.data: |
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if self.total: |
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bar_len = count * self.scale / self.total |
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hist_bar = '|%s|' % ('#' * bar_len).ljust(self.scale) |
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line = '%s %s %s' % ( |
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str(key).ljust(self.max_key_len), |
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hist_bar, |
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self.formatter(count)) |
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percent_str = format_utils.NumToPercent(count, self.total) |
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if percent_str: |
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line += ' (%s)' % percent_str |
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hist_lines.append(line) |
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return '\n'.join(hist_lines) |
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def GetKeys(self): |
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"""Returns the keys of the histogram.""" |
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return [key for key, _ in self.data]
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