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coding_style: Moved David's comments from coding_style.txt to API_coding_style.txt
author Olivier Delalleau <delallea@iro>
date Thu, 16 Sep 2010 16:24:47 -0400
parents d6d73a9f07b8
children 2da593b0f29d
rev   line source
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1 =========================
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2 Coding Style Guidelines
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3 =========================
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4
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5 Main Goals
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6 ==========
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7
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8 * Code should be compatible with Python 2.4 and above (using 2to3 for
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9 conversion to Python 3.x). This may not be possible in the short term
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10 for code dependent on Theano.
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11
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12 * Code should be easy to read, understand and update by developers and
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13 users.
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14
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15 * Code should be well-documented and well-tested.
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16
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17 Code Sample
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18 ===========
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19
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20 The following code sample illustrates many of the coding guidelines one should
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21 follow in Pylearn.
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22
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23 .. code-block:: python
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24
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25 import os, sys, time
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26
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27 Python Coding Guidelines
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28 ========================
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29
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30 Official Guidelines
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31 -------------------
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32
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33 Source Material
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34 ~~~~~~~~~~~~~~~
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35
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36 The three main documents describing our Python coding guidelines are:
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37 * `PEP 8 -- Style Guide for Python Code
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38 <http://www.python.org/dev/peps/pep-0008>`_
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39 * `PEP 257 -- Docstring Conventions
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40 <http://www.python.org/dev/peps/pep-0257>`_
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41 * `Numpy Docstring Standard
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42 <http://projects.scipy.org/numpy/wiki/CodingStyleGuidelines#docstring-standard>`_
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43 * `Google Python Style Guide
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44 <http://google-styleguide.googlecode.com/svn/trunk/pyguide.html>`_
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45
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46
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47 However, there are a few points mentioned in those documents that we decided
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48 to do differently:
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49
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50 * Use only one space (not two) after a sentence-ending period in comments.
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51
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52 Excerpts
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53 ~~~~~~~~
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54
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55 We emphasize here a few important topics that are found in the official
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56 guidelines:
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57
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58 Additional Recommendations
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59 --------------------------
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60
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61 Things you should do even if they are not listed in official guidelines:
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62
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63 * Avoid backslashes whenever possible. They make it more
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64 difficult to edit code, and they are ugly (as well as potentially
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65 dangerous if there are trailing white spaces).
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66
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67 .. code-block:: python
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68
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69 # Good.
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70 if (cond_1 and
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71 cond_2 and
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72 cond_3):
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73 ...
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74 # Bad.
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75 if cond_1 and \
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76 cond_2 and \
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77 cond_3:
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78 ...
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79
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80 * When indenting multi-line statements like lists or function arguments,
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81 keep elements of the same level aligned with each other.
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82 The position of the first
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83 element (on the same line or a new line) should be chosen depending on
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84 what is easiest to read (sometimes both can be ok).
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85
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86 .. code-block:: python
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87
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88 # Good.
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89 for my_very_long_variable_name in [my_food, my_bar, my_love,
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90 my_everything]:
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91 ...
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92 for my_very_long_variable_name in [
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93 my_foo, my_bar, my_love, my_everything]:
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94 ...
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95 # Good iff the list needs to be frequently updated.
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96 for my_very_long_variable_name in [
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97 my_foo,
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98 my_bar,
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99 my_love,
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100 my_everything,
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101 ]:
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102 ...
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103 # Bad.
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104 for my_very_long_variable_name in [my_foo, my_bar, my_love,
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105 my_everything]:
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106 ...
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107 for my_very_long_variable_name in [my_foo,
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108 my_bar,
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109 my_love,
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110 my_everything]:
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111 ...
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112
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113 The ``logging`` Module vs. the ``warning`` Module
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114 =================================================
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115
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116 The ``logging`` Module
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117 ----------------------
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118
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119 A central logging facility for Python capable of logging messages of various
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120 categories/urgency and choosing with some granularity which messages are
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121 displayed/suppressed, as well as where they are displayed or written. This
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122 includes an ``INFO`` level for innocuous status information, a ``WARNING`` level
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123 for unexpected state that is still recoverable, ``DEBUG`` for detailed
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124 information which is only really of interest when things are going wrong, etc.
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125
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126 In addition to the `library documentation`_, see this helpful tutorial,
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127 `Python Logging 101`_.
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128
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129 .. _library documentation: http://docs.python.org/library/logging.html
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130 .. _Python Logging 101: http://plumberjack.blogspot.com/2009/09/python-logging-101.html
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131
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132 The ``warning`` Module
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133 ----------------------
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134
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135 The ``warning`` module in the standard library and its main interface, the
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136 ``warn()`` function, allows the programmer to issue warnings in situations where
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137 they wish to alert the user to some condition, but the situation is not
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138 urgent enough to throw an exception. By default, a warning issued at a given
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139 line of the code will only be displayed the first time that line is executed.
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140 By default, warnings are written to ``sys.stderr`` but the ``warning`` module
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141 contains flexible facilities for altering the defaults, redirecting, etc.
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142
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143 Which? When?
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144 ------------
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145
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146 It is our feeling that the ``logging`` module's ``WARNING`` level be used to log
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147 warnings more meant for *internal*, *developer* consumption, to log situations
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148 where something unexpected happened that may be indicative of a problem but
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149 is several layers of abstraction below what a user of the library would
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150 care about.
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151
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152 By contrast, the warning module should be used for warnings intended for user
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153 consumption, e.g. alerting them that their version of Pylearn is older than
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154 this plugin requires, so things may not work as expected, or that a given
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155 function/class/method is slated for deprecation in a coming release (early
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156 in the library's lifetime, ``DeprecationWarning`` will likely be the most common
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157 case). The warning message issued through this facility should avoid
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158 referring to Pylearn internals.
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159