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55 | <H2><A NAME="SECTION00121010000000000000000"> | |
56 | 10.10.1 Command Line Interface</A> | |
57 | </H2> | |
58 | ||
59 | <P> | |
60 | When called as a program from the command line, the following form is used: | |
61 | ||
62 | <P> | |
63 | <div class="verbatim"><pre> | |
64 | python timeit.py [-n N] [-r N] [-s S] [-t] [-c] [-h] [statement ...] | |
65 | </pre></div> | |
66 | ||
67 | <P> | |
68 | where the following options are understood: | |
69 | ||
70 | <P> | |
71 | <DL> | |
72 | <DT><STRONG>-n N/<b class="programopt">--number=N</b></STRONG></DT> | |
73 | <DD>how many times to execute 'statement' | |
74 | </DD> | |
75 | <DT><STRONG>-r N/<b class="programopt">--repeat=N</b></STRONG></DT> | |
76 | <DD>how many times to repeat the timer (default 3) | |
77 | </DD> | |
78 | <DT><STRONG>-s S/<b class="programopt">--setup=S</b></STRONG></DT> | |
79 | <DD>statement to be executed once initially (default | |
80 | <code>'pass'</code>) | |
81 | </DD> | |
82 | <DT><STRONG>-t/<b class="programopt">--time</b></STRONG></DT> | |
83 | <DD>use <tt class="function">time.time()</tt> | |
84 | (default on all platforms but Windows) | |
85 | </DD> | |
86 | <DT><STRONG>-c/<b class="programopt">--clock</b></STRONG></DT> | |
87 | <DD>use <tt class="function">time.clock()</tt> (default on Windows) | |
88 | </DD> | |
89 | <DT><STRONG>-v/<b class="programopt">--verbose</b></STRONG></DT> | |
90 | <DD>print raw timing results; repeat for more digits | |
91 | precision | |
92 | </DD> | |
93 | <DT><STRONG>-h/<b class="programopt">--help</b></STRONG></DT> | |
94 | <DD>print a short usage message and exit | |
95 | </DD> | |
96 | </DL> | |
97 | ||
98 | <P> | |
99 | A multi-line statement may be given by specifying each line as a | |
100 | separate statement argument; indented lines are possible by enclosing | |
101 | an argument in quotes and using leading spaces. Multiple | |
102 | <b class="programopt">-s</b> options are treated similarly. | |
103 | ||
104 | <P> | |
105 | If <b class="programopt">-n</b> is not given, a suitable number of loops is | |
106 | calculated by trying successive powers of 10 until the total time is | |
107 | at least 0.2 seconds. | |
108 | ||
109 | <P> | |
110 | The default timer function is platform dependent. On Windows, | |
111 | <tt class="function">time.clock()</tt> has microsecond granularity but | |
112 | <tt class="function">time.time()</tt>'s granularity is 1/60th of a second; on <span class="Unix">Unix</span>, | |
113 | <tt class="function">time.clock()</tt> has 1/100th of a second granularity and | |
114 | <tt class="function">time.time()</tt> is much more precise. On either platform, the | |
115 | default timer functions measure wall clock time, not the CPU time. | |
116 | This means that other processes running on the same computer may | |
117 | interfere with the timing. The best thing to do when accurate timing | |
118 | is necessary is to repeat the timing a few times and use the best | |
119 | time. The <b class="programopt">-r</b> option is good for this; the default of 3 | |
120 | repetitions is probably enough in most cases. On <span class="Unix">Unix</span>, you can use | |
121 | <tt class="function">time.clock()</tt> to measure CPU time. | |
122 | ||
123 | <P> | |
124 | <div class="note"><b class="label">Note:</b> | |
125 | There is a certain baseline overhead associated with executing a | |
126 | pass statement. The code here doesn't try to hide it, but you | |
127 | should be aware of it. The baseline overhead can be measured by | |
128 | invoking the program without arguments. | |
129 | </div> | |
130 | ||
131 | <P> | |
132 | The baseline overhead differs between Python versions! Also, to | |
133 | fairly compare older Python versions to Python 2.3, you may want to | |
134 | use Python's <b class="programopt">-O</b> option for the older versions to avoid | |
135 | timing <code>SET_LINENO</code> instructions. | |
136 | ||
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