python idle 解释和直接 python script.py 解释有什么差别？-Python教程-PHP中文网

python idle 解释和直接 python script.py 解释有什么差别？
php中文网
发布： 2016-06-06 16:22:18
原创
1656人浏览过
回复内容：

题主想的“逐行解释”与“整体解释”的差异的思路是对的，不过细节不太对。下面讲点细节。
跟Sublime、IDLE啥的没关系。
<span class="err">$</span> <span class="n">python</span>
<span class="n">Python</span> <span class="mf">2.7</span><span class="o">.</span><span class="mi">5</span> <span class="p">(</span><span class="n">default</span><span class="p">,</span> <span class="n">Mar</span>  <span class="mi">9</span> <span class="mi">2014</span><span class="p">,</span> <span class="mi">22</span><span class="p">:</span><span class="mi">15</span><span class="p">:</span><span class="mo">05</span><span class="p">)</span> 
<span class="p">[</span><span class="n">GCC</span> <span class="mf">4.2</span><span class="o">.</span><span class="mi">1</span> <span class="n">Compatible</span> <span class="n">Apple</span> <span class="n">LLVM</span> <span class="mf">5.0</span> <span class="p">(</span><span class="n">clang</span><span class="o">-</span><span class="mf">500.0</span><span class="o">.</span><span class="mi">68</span><span class="p">)]</span> <span class="n">on</span> <span class="n">darwin</span>
<span class="n">Type</span> <span class="s">"help"</span><span class="p">,</span> <span class="s">"copyright"</span><span class="p">,</span> <span class="s">"credits"</span> <span class="ow">or</span> <span class="s">"license"</span> <span class="k">for</span> <span class="n">more</span> <span class="n">information</span><span class="o">.</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">=</span> <span class="mf">10.1</span>
<span class="o">>>></span> <span class="n">b</span> <span class="o">=</span> <span class="mf">10.1</span>
<span class="o">>>></span> <span class="n">a</span> <span class="ow">is</span> <span class="n">b</span>
<span class="bp">False</span>
<span class="o">>>></span> <span class="nb">id</span><span class="p">(</span><span class="n">a</span><span class="p">)</span>
<span class="mi">140475784803760</span>
<span class="o">>>></span> <span class="nb">id</span><span class="p">(</span><span class="n">b</span><span class="p">)</span>
<span class="mi">140475784803736</span>
<span class="o">>>></span> <span class="p">(</span><span class="mf">10.1</span><span class="p">)</span> <span class="ow">is</span> <span class="p">(</span><span class="mf">10.1</span><span class="p">)</span>
<span class="bp">True</span>
<span class="o">>>></span> <span class="k">def</span> <span class="nf">foo</span><span class="p">():</span>
<span class="o">...</span>   <span class="n">a</span> <span class="o">=</span> <span class="mf">10.1</span>
<span class="o">...</span>   <span class="n">b</span> <span class="o">=</span> <span class="mf">10.1</span>
<span class="o">...</span>   <span class="k">return</span> <span class="n">a</span> <span class="ow">is</span> <span class="n">b</span>
<span class="o">...</span> 
<span class="o">>>></span> <span class="n">foo</span><span class="p">()</span>
<span class="bp">True</span>
登录后复制
is 是判断identity的，如果两个变量 id (address)相同，那么a is b就是True;
所以从执行结果来看，也是符合的。

至于问题中的差别，那就是实现相关的，像10.1这样的small number是否再次赋值会复用id那是实现相关的（我的2.7.6是不同的id）；我估计可能sublime本身内置有python的运行时（不太确定，我不大用sublime），所以会出现不同的表现。

给自己埋个坑，今天突然想到了一种可能，由于IDLE是逐条解释命令的，而python中的浮点数保存在堆内存中，每次创建一个浮点数，都会直接将堆内存地址压栈，创建相同浮点数时，IDLE也会执行重复动作；而当写到脚本中，用解释器执行时，碰到简单的数值对象，就会检查是否已经存在该对象（数值对象重复判断比较简单），从而直接将存在的堆地址压栈即可。
应该是python的解释器存在朱涛所说的运行时，究竟如何要以后看了解释器的实现过程才明白了。等以后填坑。