在 Python 代码中,定义一个支持 write()
方法的对象。 将此对象赋值给 sys.stdout
和 sys.stderr
。 调用 print_error 或者只是允许标准回溯机制生效。 在此之后,输出将转往你的 write()
方法所指向的任何地方。
做到这一点的最简单方式是使用 io.StringIO
类:
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">io</span><span class="o">,</span> <span class="nn">sys</span>
<span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span> <span class="o">=</span> <span class="n">io</span><span class="o">.</span><span class="n">StringIO</span><span class="p">()</span>
<span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="s1">"foo"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="s1">"hello world!"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="o">.</span><span class="n">getvalue</span><span class="p">())</span>
<span class="go">foo</span>
<span class="go">hello world!</span>
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实现同样效果的自定义对象看起来是这样的:
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">io</span><span class="o">,</span> <span class="nn">sys</span>
<span class="gp">>>> </span><span class="k">class</span> <span class="nc">StdoutCatcher</span><span class="p">(</span><span class="n">io</span><span class="o">.</span><span class="n">TextIOBase</span><span class="p">):</span>
<span class="gp">... </span> <span class="k">def</span> <span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">data</span> <span class="o">=</span> <span class="p">[]</span>
<span class="gp">... </span> <span class="k">def</span> <span class="nf">write</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">stuff</span><span class="p">):</span>
<span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">data</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">stuff</span><span class="p">)</span>
<span class="gp">...</span>
<span class="gp">>>> </span><span class="kn">import</span> <span class="nn">sys</span>
<span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span> <span class="o">=</span> <span class="n">StdoutCatcher</span><span class="p">()</span>
<span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="s1">"foo"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="nb">print</span><span class="p">(</span><span class="s1">"hello world!"</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">sys</span><span class="o">.</span><span class="n">stderr</span><span class="o">.</span><span class="n">write</span><span class="p">(</span><span class="s1">""</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="n">sys</span><span class="o">.</span><span class="n">stdout</span><span class="o">.</span><span class="n">data</span><span class="p">))</span>
<span class="go">foo</span>
<span class="go">hello world!</span>
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