projects / OpenSPARC-T2-DV / blame
? search:
summary | tags | clone url | shortlog | log | commit | commitdiff | tree
blob | blame (incremental) | history | HEAD
Initial commit of OpenSPARC T2 design and verification files.
[OpenSPARC-T2-DV] / tools / src / nas,5.n2.os.2 / lib / python / html / python / lib / doctest-warnings.html
CommitLineData
86530b38
AT		 1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
2<html>
3<head>
4<link rel="STYLESHEET" href="lib.css" type='text/css' />
5<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
6<link rel='start' href='../index.html' title='Python Documentation Index' />
7<link rel="first" href="lib.html" title='Python Library Reference' />
8<link rel='contents' href='contents.html' title="Contents" />
9<link rel='index' href='genindex.html' title='Index' />
10<link rel='last' href='about.html' title='About this document...' />
11<link rel='help' href='about.html' title='About this document...' />
12<link rel="prev" href="doctest-options.html" />
13<link rel="parent" href="doctest-how-it-works.html" />
14<link rel="next" href="doctest-basic-api.html" />
15<meta name='aesop' content='information' />
16<title>5.2.3.6 Warnings</title>
17</head>
18<body>
19<DIV CLASS="navigation">
20<div id='top-navigation-panel' xml:id='top-navigation-panel'>
21<table align="center" width="100%" cellpadding="0" cellspacing="2">
22<tr>
23<td class='online-navigation'><a rel="prev" title="5.2.3.5 Option Flags and"
24 href="doctest-options.html"><img src='../icons/previous.png'
25 border='0' height='32' alt='Previous Page' width='32' /></A></td>
26<td class='online-navigation'><a rel="parent" title="5.2.3 How It Works"
27 href="doctest-how-it-works.html"><img src='../icons/up.png'
28 border='0' height='32' alt='Up One Level' width='32' /></A></td>
29<td class='online-navigation'><a rel="next" title="5.2.4 Basic API"
30 href="doctest-basic-api.html"><img src='../icons/next.png'
31 border='0' height='32' alt='Next Page' width='32' /></A></td>
32<td align="center" width="100%">Python Library Reference</td>
33<td class='online-navigation'><a rel="contents" title="Table of Contents"
34 href="contents.html"><img src='../icons/contents.png'
35 border='0' height='32' alt='Contents' width='32' /></A></td>
36<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
37 border='0' height='32' alt='Module Index' width='32' /></a></td>
38<td class='online-navigation'><a rel="index" title="Index"
39 href="genindex.html"><img src='../icons/index.png'
40 border='0' height='32' alt='Index' width='32' /></A></td>
41</tr></table>
42<div class='online-navigation'>
43<b class="navlabel">Previous:</b>
44<a class="sectref" rel="prev" href="doctest-options.html">5.2.3.5 Option Flags and</A>
45<b class="navlabel">Up:</b>
46<a class="sectref" rel="parent" href="doctest-how-it-works.html">5.2.3 How It Works</A>
47<b class="navlabel">Next:</b>
48<a class="sectref" rel="next" href="doctest-basic-api.html">5.2.4 Basic API</A>
49</div>
50<hr /></div>
51</DIV>
52<!--End of Navigation Panel-->
53
54<H3><A NAME="SECTION007236000000000000000"></A><A NAME="doctest-warnings"></A>
55<BR>
565.2.3.6 Warnings
57</H3>
58
59<P>
60<tt class="module"><a href="module-doctest.html">doctest</a></tt> is serious about requiring exact matches in expected
61output. If even a single character doesn't match, the test fails. This
62will probably surprise you a few times, as you learn exactly what Python
63does and doesn't guarantee about output. For example, when printing a
64dict, Python doesn't guarantee that the key-value pairs will be printed
65in any particular order, so a test like
66
67<P>
68<div class="verbatim"><pre>
69&gt;&gt;&gt; foo()
70{"Hermione": "hippogryph", "Harry": "broomstick"}
71</pre></div>
72
73<P>
74is vulnerable! One workaround is to do
75
76<P>
77<div class="verbatim"><pre>
78&gt;&gt;&gt; foo() == {"Hermione": "hippogryph", "Harry": "broomstick"}
79True
80</pre></div>
81
82<P>
83instead. Another is to do
84
85<P>
86<div class="verbatim"><pre>
87&gt;&gt;&gt; d = foo().items()
88&gt;&gt;&gt; d.sort()
89&gt;&gt;&gt; d
90[('Harry', 'broomstick'), ('Hermione', 'hippogryph')]
91</pre></div>
92
93<P>
94There are others, but you get the idea.
95
96<P>
97Another bad idea is to print things that embed an object address, like
98
99<P>
100<div class="verbatim"><pre>
101&gt;&gt;&gt; id(1.0) # certain to fail some of the time
1027948648
103&gt;&gt;&gt; class C: pass
104&gt;&gt;&gt; C() # the default repr() for instances embeds an address
105&lt;__main__.C instance at 0x00AC18F0&gt;
106</pre></div>
107
108<P>
109The <tt class="constant">ELLIPSIS</tt> directive gives a nice approach for the last
110example:
111
112<P>
113<div class="verbatim"><pre>
114&gt;&gt;&gt; C() #doctest: +ELLIPSIS
115&lt;__main__.C instance at 0x...&gt;
116</pre></div>
117
118<P>
119Floating-point numbers are also subject to small output variations across
120platforms, because Python defers to the platform C library for float
121formatting, and C libraries vary widely in quality here.
122
123<P>
124<div class="verbatim"><pre>
125&gt;&gt;&gt; 1./7 # risky
1260.14285714285714285
127&gt;&gt;&gt; print 1./7 # safer
1280.142857142857
129&gt;&gt;&gt; print round(1./7, 6) # much safer
1300.142857
131</pre></div>
132
133<P>
134Numbers of the form <code>I/2.**J</code> are safe across all platforms, and I
135often contrive doctest examples to produce numbers of that form:
136
137<P>
138<div class="verbatim"><pre>
139&gt;&gt;&gt; 3./4 # utterly safe
1400.75
141</pre></div>
142
143<P>
144Simple fractions are also easier for people to understand, and that makes
145for better documentation.
146
147<P>
148
149<DIV CLASS="navigation">
150<div class='online-navigation'>
151<p></p><hr />
152<table align="center" width="100%" cellpadding="0" cellspacing="2">
153<tr>
154<td class='online-navigation'><a rel="prev" title="5.2.3.5 Option Flags and"
155 href="doctest-options.html"><img src='../icons/previous.png'
156 border='0' height='32' alt='Previous Page' width='32' /></A></td>
157<td class='online-navigation'><a rel="parent" title="5.2.3 How It Works"
158 href="doctest-how-it-works.html"><img src='../icons/up.png'
159 border='0' height='32' alt='Up One Level' width='32' /></A></td>
160<td class='online-navigation'><a rel="next" title="5.2.4 Basic API"
161 href="doctest-basic-api.html"><img src='../icons/next.png'
162 border='0' height='32' alt='Next Page' width='32' /></A></td>
163<td align="center" width="100%">Python Library Reference</td>
164<td class='online-navigation'><a rel="contents" title="Table of Contents"
165 href="contents.html"><img src='../icons/contents.png'
166 border='0' height='32' alt='Contents' width='32' /></A></td>
167<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
168 border='0' height='32' alt='Module Index' width='32' /></a></td>
169<td class='online-navigation'><a rel="index" title="Index"
170 href="genindex.html"><img src='../icons/index.png'
171 border='0' height='32' alt='Index' width='32' /></A></td>
172</tr></table>
173<div class='online-navigation'>
174<b class="navlabel">Previous:</b>
175<a class="sectref" rel="prev" href="doctest-options.html">5.2.3.5 Option Flags and</A>
176<b class="navlabel">Up:</b>
177<a class="sectref" rel="parent" href="doctest-how-it-works.html">5.2.3 How It Works</A>
178<b class="navlabel">Next:</b>
179<a class="sectref" rel="next" href="doctest-basic-api.html">5.2.4 Basic API</A>
180</div>
181</div>
182<hr />
183<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
184</DIV>
185<!--End of Navigation Panel-->
186<ADDRESS>
187See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
188</ADDRESS>
189</BODY>
190</HTML>
Full OpenSPARC design & verification tarball including full HDL.