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Dịch ngược mã máy Python: import
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<p>Tiếp loạt bài về <a href="./compile.html">CPython compiler</a></p>
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<div class="highlight"><pre><span></span><code> <span class="n">rand</span><span class="o">.</span><span class="n">py</span>
<span class="mi">1</span> <span class="kn">import</span> <span class="nn">random</span>
<span class="mi">2</span> <span class="n">do</span> <span class="o">=</span> <span class="n">random</span><span class="o">.</span><span class="n">choice</span><span class="p">([</span><span class="s1">'an'</span><span class="p">,</span> <span class="s1">'ngu'</span><span class="p">])</span>
<span class="mi">3</span> <span class="nb">print</span><span class="p">(</span><span class="n">do</span><span class="p">)</span>
<span class="mi">4</span>
<span class="mi">5</span> <span class="kn">from</span> <span class="nn">datetime</span> <span class="kn">import</span> <span class="n">timedelta</span>
<span class="mi">6</span> <span class="nb">print</span><span class="p">(</span><span class="s2">"Mot ngay co: </span><span class="si">{}</span><span class="s2">s"</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">timedelta</span><span class="p">(</span><span class="n">days</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">total_seconds</span><span class="p">()))</span>
<span class="mi">7</span>
<span class="mi">8</span> <span class="kn">from</span> <span class="nn">math</span> <span class="kn">import</span> <span class="o">*</span>
<span class="mi">9</span> <span class="nb">print</span><span class="p">(</span><span class="n">factorial</span><span class="p">(</span><span class="mi">5</span><span class="p">))</span>
</code></pre></div>
<p>3 kiểu import trong Python.
Chạy dis:</p>
<div class="highlight"><pre><span></span><code><span class="c1"># python3 -m dis rand.py</span>
<span class="mi">1</span> <span class="mi">0</span> <span class="n">LOAD_CONST</span> <span class="mi">0</span> <span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="mi">2</span> <span class="n">LOAD_CONST</span> <span class="mi">1</span> <span class="p">(</span><span class="kc">None</span><span class="p">)</span>
<span class="mi">4</span> <span class="n">IMPORT_NAME</span> <span class="mi">0</span> <span class="p">(</span><span class="n">random</span><span class="p">)</span>
<span class="mi">6</span> <span class="n">STORE_NAME</span> <span class="mi">0</span> <span class="p">(</span><span class="n">random</span><span class="p">)</span>
<span class="mi">2</span> <span class="mi">8</span> <span class="n">LOAD_NAME</span> <span class="mi">0</span> <span class="p">(</span><span class="n">random</span><span class="p">)</span>
<span class="mi">10</span> <span class="n">LOAD_METHOD</span> <span class="mi">1</span> <span class="p">(</span><span class="n">choice</span><span class="p">)</span>
<span class="mi">12</span> <span class="n">LOAD_CONST</span> <span class="mi">2</span> <span class="p">(</span><span class="s1">'an'</span><span class="p">)</span>
<span class="mi">14</span> <span class="n">LOAD_CONST</span> <span class="mi">3</span> <span class="p">(</span><span class="s1">'ngu'</span><span class="p">)</span>
<span class="mi">16</span> <span class="n">BUILD_LIST</span> <span class="mi">2</span>
<span class="mi">18</span> <span class="n">CALL_METHOD</span> <span class="mi">1</span>
<span class="mi">20</span> <span class="n">STORE_NAME</span> <span class="mi">2</span> <span class="p">(</span><span class="n">do</span><span class="p">)</span>
<span class="mi">3</span> <span class="mi">22</span> <span class="n">LOAD_NAME</span> <span class="mi">3</span> <span class="p">(</span><span class="nb">print</span><span class="p">)</span>
<span class="mi">24</span> <span class="n">LOAD_NAME</span> <span class="mi">2</span> <span class="p">(</span><span class="n">do</span><span class="p">)</span>
<span class="mi">26</span> <span class="n">CALL_FUNCTION</span> <span class="mi">1</span>
<span class="mi">28</span> <span class="n">POP_TOP</span>
<span class="mi">5</span> <span class="mi">30</span> <span class="n">LOAD_CONST</span> <span class="mi">0</span> <span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="mi">32</span> <span class="n">LOAD_CONST</span> <span class="mi">4</span> <span class="p">((</span><span class="s1">'timedelta'</span><span class="p">,))</span>
<span class="mi">34</span> <span class="n">IMPORT_NAME</span> <span class="mi">4</span> <span class="p">(</span><span class="n">datetime</span><span class="p">)</span>
<span class="mi">36</span> <span class="n">IMPORT_FROM</span> <span class="mi">5</span> <span class="p">(</span><span class="n">timedelta</span><span class="p">)</span>
<span class="mi">38</span> <span class="n">STORE_NAME</span> <span class="mi">5</span> <span class="p">(</span><span class="n">timedelta</span><span class="p">)</span>
<span class="mi">40</span> <span class="n">POP_TOP</span>
<span class="mi">6</span> <span class="mi">42</span> <span class="n">LOAD_NAME</span> <span class="mi">3</span> <span class="p">(</span><span class="nb">print</span><span class="p">)</span>
<span class="mi">44</span> <span class="n">LOAD_CONST</span> <span class="mi">5</span> <span class="p">(</span><span class="s1">'Mot ngay co: </span><span class="si">{}</span><span class="s1">s'</span><span class="p">)</span>
<span class="mi">46</span> <span class="n">LOAD_METHOD</span> <span class="mi">6</span> <span class="p">(</span><span class="nb">format</span><span class="p">)</span>
<span class="mi">48</span> <span class="n">LOAD_NAME</span> <span class="mi">5</span> <span class="p">(</span><span class="n">timedelta</span><span class="p">)</span>
<span class="mi">50</span> <span class="n">LOAD_CONST</span> <span class="mi">6</span> <span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="mi">52</span> <span class="n">LOAD_CONST</span> <span class="mi">7</span> <span class="p">((</span><span class="s1">'days'</span><span class="p">,))</span>
<span class="mi">54</span> <span class="n">CALL_FUNCTION_KW</span> <span class="mi">1</span>
<span class="mi">56</span> <span class="n">LOAD_METHOD</span> <span class="mi">7</span> <span class="p">(</span><span class="n">total_seconds</span><span class="p">)</span>
<span class="mi">58</span> <span class="n">CALL_METHOD</span> <span class="mi">0</span>
<span class="mi">60</span> <span class="n">CALL_METHOD</span> <span class="mi">1</span>
<span class="mi">62</span> <span class="n">CALL_FUNCTION</span> <span class="mi">1</span>
<span class="mi">64</span> <span class="n">POP_TOP</span>
<span class="mi">8</span> <span class="mi">66</span> <span class="n">LOAD_CONST</span> <span class="mi">0</span> <span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="mi">68</span> <span class="n">LOAD_CONST</span> <span class="mi">8</span> <span class="p">((</span><span class="s1">'*'</span><span class="p">,))</span>
<span class="mi">70</span> <span class="n">IMPORT_NAME</span> <span class="mi">8</span> <span class="p">(</span><span class="n">math</span><span class="p">)</span>
<span class="mi">72</span> <span class="n">IMPORT_STAR</span>
<span class="mi">9</span> <span class="mi">74</span> <span class="n">LOAD_NAME</span> <span class="mi">3</span> <span class="p">(</span><span class="nb">print</span><span class="p">)</span>
<span class="mi">76</span> <span class="n">LOAD_NAME</span> <span class="mi">9</span> <span class="p">(</span><span class="n">factorial</span><span class="p">)</span>
<span class="mi">78</span> <span class="n">LOAD_CONST</span> <span class="mi">9</span> <span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<span class="mi">80</span> <span class="n">CALL_FUNCTION</span> <span class="mi">1</span>
<span class="mi">82</span> <span class="n">CALL_FUNCTION</span> <span class="mi">1</span>
<span class="mi">84</span> <span class="n">POP_TOP</span>
<span class="mi">86</span> <span class="n">LOAD_CONST</span> <span class="mi">1</span> <span class="p">(</span><span class="kc">None</span><span class="p">)</span>
<span class="mi">88</span> <span class="n">RETURN_VALUE</span>
</code></pre></div>
<p><code>import random</code> sẽ dùng <span class="caps">BYTECODE</span> <code>IMPORT_NAME</code>, random sẽ trở thành 1 name
trong module này, được chứa <code>STORE_NAME</code> tương tự khi đặt <code>x = 5</code>.
Để gọi random.choice, đầu tiên phải
<code>LOAD_NAME</code> random rồi <code>LOAD_METHOD</code> choice.</p>
<p>Code <code>from datetime import timedelta</code>, chạy <code>IMPORT_NAME</code> datetime, nhưng không
<code>STORE_NAME</code> này mà <code>IMPORT_FROM</code> timedelta rồi <code>STORE_NAME</code> timedelta.</p>
<p>Code <code>from math import *</code> sử dụng <span class="caps">BYTECODE</span> <code>IMPORT_STAR</code>.</p>
<p>Chú ý khi gọi <code>random.choice</code> thì <span class="caps">BYTECODE</span> là <code>CALL_METHOD</code> do choice gắn liền
vào random - xem như 1 method của 1 module object, nhưng khi gọi
<code>factorial</code> đã <code>from math import *</code> thì <span class="caps">BYTECODE</span> là <code>CALL_FUNCTION</code>.</p>
<p>Đăng ký ngay tại <a href="https://pymi.vn">PyMI.vn</a> để học Python tại Hà Nội <span class="caps">TP</span> <span class="caps">HCM</span> (Sài Gòn),
trở thành lập trình viên #python chuyên nghiệp ngay sau khóa học.</p>
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