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Updated notes on Python 3

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Tom Keffer
2018-12-06 14:23:19 -08:00
parent c96d77428b
commit 190812a521
1 changed files with 11 additions and 10 deletions
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docs/devnotes.htm
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@@ -123,13 +123,6 @@ Version: 3.9
Conditions&quot; page takes just under 2 seconds (compared with 0.4 seconds for <span
class="code">wview</span>). </p>
<p>Unfortunately, the architectural goal of one code base is likely to be broken with the arrival of Python
V3.X. It has so many changes that are not backwards compatible with V2.X, that a separate code base will
most likely be needed. My intention is to stick with the V2.X versions until V3.X is so widespread it cannot
be ignored, then make a permanent switch. Given the slow adoption rate of V3.X this is unlikely to happen
anytime soon. In any case, I doubt the transition will affect the average WeeWX
user. </p>
<p>All writes to the databases are protected by transactions. You can kill the program at any time (either
Control-C if run directly or &quot;<span class="code">/etc/init.d/weewx
stop</span>&quot; if run as a daemon) without fear of corrupting the databases. </p>
@@ -146,6 +139,12 @@ Version: 3.9
affected &mdash; the main thread will continue downloading data off the instrument and putting them in the
database. You can fix the problem at your leisure, without worrying about losing any data. </p>
<p>
For now, WeeWX requires Python v2.6 or v2.7. However, we eventually plan on supporting Python v3.x as well.
See the Wiki page <a href="https://github.com/weewx/weewx/wiki/Python-3-strategy"><em>Python 3 strategy</em></a>
for details on the transition.
</p>
<h1>Units</h1>
<p>In general, there are three different areas where the unit system makes a difference: </p>
@@ -171,9 +170,11 @@ Version: 3.9
because of a failed checksum). If the hardware simply doesn't support it, then the driver should not emit a
value at all.</p>
<p>The same rule applies to derived values. If the input data for a derived value are missing, then no derived
<p>
The same rule applies to derived values. If the input data for a derived value are missing, then no derived
value should be emitted. However, if the input values are present, but have value
<span class="code">None</span></p>, then the derived value should be set to <span class="code">None</span>.
<span class="code">None</span>, then the derived value should be set to <span class="code">None</span>.
</p>
<p>However, the time value must never be <span class="code">None</span>. This is because it is used as the
primary key in the SQL database. </p>
@@ -210,7 +211,7 @@ next_ts = int(time.mktime(next_dt.timetuple()))</pre>
</p>
<h1>Internationalization</h1>
<p>Generally, weewx does not make much use of Unicode. This is because the Python 2.x libraries do not always
<p>Generally, WeeWX does not make much use of Unicode. This is because the Python 2.x libraries do not always
handle it correctly. In particular, the function <span class="code">time.strftime()</span> completely fails
when handed a Unicode string with a non-ASCII character. As this function is often used by extensions,
working around this bug is an unfair expectation on extension writers. So, we generally avoid Unicode.</p>