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Removed Using Abstract Syntax Trees
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‎README.md

Lines changed: 0 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -1635,7 +1635,6 @@ last_el = op.methodcaller('pop')(<list>)
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Eval
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----
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### Basic
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```python
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>>> from ast import literal_eval
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>>> literal_eval('1 + 2')
@@ -1646,51 +1645,6 @@ Eval
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ValueError: malformed node or string
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```
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### Using Abstract Syntax Trees
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```python
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import ast
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from ast import Num, BinOp, UnaryOp
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import operator as op
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LEGAL_OPERATORS = {ast.Add: op.add, # <el> + <el>
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ast.Sub: op.sub, # <el> - <el>
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ast.Mult: op.mul, # <el> * <el>
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ast.Div: op.truediv, # <el> / <el>
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ast.Pow: op.pow, # <el> ** <el>
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ast.BitXor: op.xor, # <el> ^ <el>
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ast.USub: op.neg} # - <el>
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def evaluate(expression):
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root = ast.parse(expression, mode='eval')
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return eval_node(root.body)
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def eval_node(node):
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node_type = type(node)
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if node_type == Num:
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return node.n
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if node_type not in [BinOp, UnaryOp]:
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raise TypeError(node)
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operator_type = type(node.op)
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if operator_type not in LEGAL_OPERATORS:
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raise TypeError(f'Illegal operator {node.op}')
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operator = LEGAL_OPERATORS[operator_type]
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if node_type == BinOp:
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left, right = eval_node(node.left), eval_node(node.right)
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return operator(left, right)
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elif node_type == UnaryOp:
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operand = eval_node(node.operand)
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return operator(operand)
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```
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```python
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>>> evaluate('2 ^ 6')
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4
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>>> evaluate('2 ** 6')
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64
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>>> evaluate('1 + 2 * 3 ** (4 ^ 5) / (6 + -7)')
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-5.0
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```
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Coroutine
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---------

‎index.html

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Original file line numberDiff line numberDiff line change
@@ -1387,7 +1387,6 @@ <h2 id="operator"><a href="#operator" name="operator">#</a>Operator</h2>
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last_el = op.methodcaller(<span class="hljs-string">'pop'</span>)(&lt;list&gt;)
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</code></pre>
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<h2 id="eval"><a href="#eval" name="eval">#</a>Eval</h2>
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<h3 id="basic">Basic</h3>
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<pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-keyword">from</span> ast <span class="hljs-keyword">import</span> literal_eval
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<span class="hljs-meta">&gt;&gt;&gt; </span>literal_eval(<span class="hljs-string">'1 + 2'</span>)
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<span class="hljs-number">3</span>
@@ -1396,47 +1395,6 @@ <h3 id="basic">Basic</h3>
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<span class="hljs-meta">&gt;&gt;&gt; </span>literal_eval(<span class="hljs-string">'abs(1)'</span>)
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ValueError: malformed node <span class="hljs-keyword">or</span> string
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</code></pre>
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<h3 id="usingabstractsyntaxtrees">Using Abstract Syntax Trees</h3>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">import</span> ast
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<span class="hljs-keyword">from</span> ast <span class="hljs-keyword">import</span> Num, BinOp, UnaryOp
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<span class="hljs-keyword">import</span> operator <span class="hljs-keyword">as</span> op
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LEGAL_OPERATORS = {ast.Add: op.add, <span class="hljs-comment"># &lt;el&gt; + &lt;el&gt;</span>
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ast.Sub: op.sub, <span class="hljs-comment"># &lt;el&gt; - &lt;el&gt;</span>
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ast.Mult: op.mul, <span class="hljs-comment"># &lt;el&gt; * &lt;el&gt;</span>
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ast.Div: op.truediv, <span class="hljs-comment"># &lt;el&gt; / &lt;el&gt;</span>
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ast.Pow: op.pow, <span class="hljs-comment"># &lt;el&gt; ** &lt;el&gt;</span>
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ast.BitXor: op.xor, <span class="hljs-comment"># &lt;el&gt; ^ &lt;el&gt;</span>
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ast.USub: op.neg} <span class="hljs-comment"># - &lt;el&gt;</span>
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<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">evaluate</span><span class="hljs-params">(expression)</span>:</span>
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root = ast.parse(expression, mode=<span class="hljs-string">'eval'</span>)
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<span class="hljs-keyword">return</span> eval_node(root.body)
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<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">eval_node</span><span class="hljs-params">(node)</span>:</span>
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node_type = type(node)
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<span class="hljs-keyword">if</span> node_type == Num:
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<span class="hljs-keyword">return</span> node.n
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<span class="hljs-keyword">if</span> node_type <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> [BinOp, UnaryOp]:
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<span class="hljs-keyword">raise</span> TypeError(node)
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operator_type = type(node.op)
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<span class="hljs-keyword">if</span> operator_type <span class="hljs-keyword">not</span> <span class="hljs-keyword">in</span> LEGAL_OPERATORS:
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<span class="hljs-keyword">raise</span> TypeError(<span class="hljs-string">f'Illegal operator <span class="hljs-subst">{node.op}</span>'</span>)
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operator = LEGAL_OPERATORS[operator_type]
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<span class="hljs-keyword">if</span> node_type == BinOp:
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left, right = eval_node(node.left), eval_node(node.right)
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<span class="hljs-keyword">return</span> operator(left, right)
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<span class="hljs-keyword">elif</span> node_type == UnaryOp:
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operand = eval_node(node.operand)
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<span class="hljs-keyword">return</span> operator(operand)
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</code></pre>
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<pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>evaluate(<span class="hljs-string">'2 ^ 6'</span>)
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<span class="hljs-number">4</span>
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<span class="hljs-meta">&gt;&gt;&gt; </span>evaluate(<span class="hljs-string">'2 ** 6'</span>)
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<span class="hljs-number">64</span>
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<span class="hljs-meta">&gt;&gt;&gt; </span>evaluate(<span class="hljs-string">'1 + 2 * 3 ** (4 ^ 5) / (6 + -7)'</span>)
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<span class="hljs-number">-5.0</span>
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</code></pre>
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<h2 id="coroutine"><a href="#coroutine" name="coroutine">#</a>Coroutine</h2>
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<ul>
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<li><strong>Similar to generator, but generator pulls data through the pipe with iteration, while coroutine pushes data into the pipeline with send().</strong></li>
@@ -1626,7 +1584,7 @@ <h4 id="test">Test:</h4>
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[<span class="hljs-string">'arsenal f.c.'</span>, <span class="hljs-number">2.44</span>, <span class="hljs-number">3.29</span>]
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</code></pre>
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<h2 id="profile"><a href="#profile" name="profile">#</a>Profile</h2>
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<h3 id="basic-1">Basic</h3>
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<h3 id="basic">Basic</h3>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> time <span class="hljs-keyword">import</span> time
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start_time = time() <span class="hljs-comment"># Seconds since Epoch.</span>
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...

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