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| 16 | <title>6.12.1 Scheduler Objects </title> |
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| 54 | <H2><A NAME="SECTION0081210000000000000000"></A><A NAME="scheduler-objects"></A> |
| 55 | <BR> |
| 56 | 6.12.1 Scheduler Objects |
| 57 | </H2> |
| 58 | |
| 59 | <P> |
| 60 | <tt class="class">scheduler</tt> instances have the following methods: |
| 61 | |
| 62 | <P> |
| 63 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 64 | <td><nobr><b><tt id='l2h-1982' xml:id='l2h-1982' class="method">enterabs</tt></b>(</nobr></td> |
| 65 | <td><var>time, priority, action, argument</var>)</td></tr></table></dt> |
| 66 | <dd> |
| 67 | Schedule a new event. The <var>time</var> argument should be a numeric type |
| 68 | compatible with the return value of the <var>timefunc</var> function passed |
| 69 | to the constructor. Events scheduled for |
| 70 | the same <var>time</var> will be executed in the order of their |
| 71 | <var>priority</var>. |
| 72 | |
| 73 | <P> |
| 74 | Executing the event means executing |
| 75 | <code><var>action</var>(*<var>argument</var>)</code>. <var>argument</var> must be a |
| 76 | sequence holding the parameters for <var>action</var>. |
| 77 | |
| 78 | <P> |
| 79 | Return value is an event which may be used for later cancellation of |
| 80 | the event (see <tt class="method">cancel()</tt>). |
| 81 | </dl> |
| 82 | |
| 83 | <P> |
| 84 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 85 | <td><nobr><b><tt id='l2h-1983' xml:id='l2h-1983' class="method">enter</tt></b>(</nobr></td> |
| 86 | <td><var>delay, priority, action, argument</var>)</td></tr></table></dt> |
| 87 | <dd> |
| 88 | Schedule an event for <var>delay</var> more time units. Other then the |
| 89 | relative time, the other arguments, the effect and the return value |
| 90 | are the same as those for <tt class="method">enterabs()</tt>. |
| 91 | </dl> |
| 92 | |
| 93 | <P> |
| 94 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 95 | <td><nobr><b><tt id='l2h-1984' xml:id='l2h-1984' class="method">cancel</tt></b>(</nobr></td> |
| 96 | <td><var>event</var>)</td></tr></table></dt> |
| 97 | <dd> |
| 98 | Remove the event from the queue. If <var>event</var> is not an event |
| 99 | currently in the queue, this method will raise a |
| 100 | <tt class="exception">RuntimeError</tt>. |
| 101 | </dl> |
| 102 | |
| 103 | <P> |
| 104 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 105 | <td><nobr><b><tt id='l2h-1985' xml:id='l2h-1985' class="method">empty</tt></b>(</nobr></td> |
| 106 | <td><var></var>)</td></tr></table></dt> |
| 107 | <dd> |
| 108 | Return true if the event queue is empty. |
| 109 | </dl> |
| 110 | |
| 111 | <P> |
| 112 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 113 | <td><nobr><b><tt id='l2h-1986' xml:id='l2h-1986' class="method">run</tt></b>(</nobr></td> |
| 114 | <td><var></var>)</td></tr></table></dt> |
| 115 | <dd> |
| 116 | Run all scheduled events. This function will wait |
| 117 | (using the <tt class="function">delayfunc</tt> function passed to the constructor) |
| 118 | for the next event, then execute it and so on until there are no more |
| 119 | scheduled events. |
| 120 | |
| 121 | <P> |
| 122 | Either <var>action</var> or <var>delayfunc</var> can raise an exception. In |
| 123 | either case, the scheduler will maintain a consistent state and |
| 124 | propagate the exception. If an exception is raised by <var>action</var>, |
| 125 | the event will not be attempted in future calls to <tt class="method">run()</tt>. |
| 126 | |
| 127 | <P> |
| 128 | If a sequence of events takes longer to run than the time available |
| 129 | before the next event, the scheduler will simply fall behind. No |
| 130 | events will be dropped; the calling code is responsible for canceling |
| 131 | events which are no longer pertinent. |
| 132 | </dl> |
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