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Exceptions
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‎README.md

Lines changed: 55 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -1306,36 +1306,63 @@ from functools import partial
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LogicOp = Enum('LogicOp', {'AND': partial(lambda l, r: l and r),
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'OR' : partial(lambda l, r: l or r)})
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```
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* **Another solution in this particular case, is to use `'and_'` and `'or_'` functions from module [operator](#operator) as values.**
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Exceptions
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----------
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### Basic Example
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```python
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while True:
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try:
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x = int(input('Please enter a number: '))
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except ValueError:
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print('Oops! That was no valid number. Try again...')
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else:
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print('Thank you.')
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break
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try:
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<code>
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except <exception>:
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<code>
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```
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### Complex Example
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```python
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try:
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<code_1>
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except <exception_a>:
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<code_2_a>
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except <exception_b>:
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<code_2_b>
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else:
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<code_2_c>
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finally:
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<code_3>
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```
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### Catching Exceptions
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```python
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except <exception>:
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except <exception> as <name>:
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except (<exception_1>, <exception_2>, ...):
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except (<exception_1>, <exception_2>, ...) as <name>:
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```
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* **Also catches subclasses of the exception.**
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### Raising Exceptions
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```python
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raise <exception>
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raise <exception>()
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raise <exception>(<el>)
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raise <exception>(<el_1>, <el_2>, ...)
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```
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### Raising Exception
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#### Useful built-in exceptions:
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```python
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raise ValueError('A very specific message!')
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raise ValueError('Argument is of right type but inappropriate value!')
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raise TypeError('Argument is of wrong type!')
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raise RuntimeError('None of above!')
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```
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### Finally
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#### Re-raising caught exception:
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```python
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>>> try:
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... raise KeyboardInterrupt
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... finally:
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... print('Goodbye, world!')
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Goodbye, world!
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Traceback (most recent call last):
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File "<stdin>", line 2, in <module>
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KeyboardInterrupt
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except <exception>:
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<code>
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raise
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```
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### Common Built-in Exceptions
@@ -1361,7 +1388,15 @@ BaseException
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+-- ValueError # When an argument is of right type but inappropriate value.
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+-- UnicodeError # Raised when encoding/decoding strings from/to bytes fails.
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```
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* **Appropriate built-in exceptions for user to rise are: 'ValueError', 'TypeError' and 'RuntimeError'.**
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### User-defined Exceptions
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```python
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class MyError(Exception):
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pass
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class MyInputError(MyError):
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pass
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```
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Print

‎index.html

Lines changed: 50 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -1210,28 +1210,52 @@ <h4 id="functionscannotbevaluessotheymustbewrapped">Functions can not be values,
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LogicOp = Enum(<span class="hljs-string">'LogicOp'</span>, {<span class="hljs-string">'AND'</span>: partial(<span class="hljs-keyword">lambda</span> l, r: l <span class="hljs-keyword">and</span> r),
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<span class="hljs-string">'OR'</span> : partial(<span class="hljs-keyword">lambda</span> l, r: l <span class="hljs-keyword">or</span> r)})
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</code></pre>
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<ul>
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<li><strong>Another solution in this particular case, is to use <code class="python hljs"><span class="hljs-string">'and_'</span></code> and <code class="python hljs"><span class="hljs-string">'or_'</span></code> functions from module <a href="#operator">operator</a> as values.</strong></li>
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</ul>
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<h2 id="exceptions"><a href="#exceptions" name="exceptions">#</a>Exceptions</h2>
1214-
<pre><code class="python language-python hljs"><span class="hljs-keyword">while</span> <span class="hljs-keyword">True</span>:
1215-
<span class="hljs-keyword">try</span>:
1216-
x = int(input(<span class="hljs-string">'Please enter a number: '</span>))
1217-
<span class="hljs-keyword">except</span> ValueError:
1218-
print(<span class="hljs-string">'Oops! That was no valid number. Try again...'</span>)
1219-
<span class="hljs-keyword">else</span>:
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print(<span class="hljs-string">'Thank you.'</span>)
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<span class="hljs-keyword">break</span>
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<h3 id="basicexample">Basic Example</h3>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">try</span>:
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&lt;code&gt;
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<span class="hljs-keyword">except</span> &lt;exception&gt;:
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&lt;code&gt;
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</code></pre>
1223-
<h3 id="raisingexception">Raising Exception</h3>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">raise</span> ValueError(<span class="hljs-string">'A very specific message!'</span>)
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<h3 id="complexexample">Complex Example</h3>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">try</span>:
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&lt;code_1&gt;
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<span class="hljs-keyword">except</span> &lt;exception_a&gt;:
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&lt;code_2_a&gt;
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<span class="hljs-keyword">except</span> &lt;exception_b&gt;:
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&lt;code_2_b&gt;
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<span class="hljs-keyword">else</span>:
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&lt;code_2_c&gt;
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<span class="hljs-keyword">finally</span>:
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&lt;code_3&gt;
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</code></pre>
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<h3 id="catchingexceptions">Catching Exceptions</h3>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">except</span> &lt;exception&gt;:
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<span class="hljs-keyword">except</span> &lt;exception&gt; <span class="hljs-keyword">as</span> &lt;name&gt;:
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<span class="hljs-keyword">except</span> (&lt;exception_1&gt;, &lt;exception_2&gt;, ...):
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<span class="hljs-keyword">except</span> (&lt;exception_1&gt;, &lt;exception_2&gt;, ...) <span class="hljs-keyword">as</span> &lt;name&gt;:
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</code></pre>
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<h3 id="finally">Finally</h3>
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<pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span><span class="hljs-keyword">try</span>:
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<span class="hljs-meta">... </span> <span class="hljs-keyword">raise</span> KeyboardInterrupt
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<span class="hljs-meta">... </span><span class="hljs-keyword">finally</span>:
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<span class="hljs-meta">... </span> print(<span class="hljs-string">'Goodbye, world!'</span>)
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Goodbye, world!
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Traceback (most recent call last):
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File <span class="hljs-string">"&lt;stdin&gt;"</span>, line <span class="hljs-number">2</span>, <span class="hljs-keyword">in</span> &lt;module&gt;
1234-
KeyboardInterrupt
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<ul>
1242+
<li><strong>Also catches subclasses of the exception.</strong></li>
1243+
</ul>
1244+
<h3 id="raisingexceptions">Raising Exceptions</h3>
1245+
<pre><code class="python language-python hljs"><span class="hljs-keyword">raise</span> &lt;exception&gt;
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<span class="hljs-keyword">raise</span> &lt;exception&gt;()
1247+
<span class="hljs-keyword">raise</span> &lt;exception&gt;(&lt;el&gt;)
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<span class="hljs-keyword">raise</span> &lt;exception&gt;(&lt;el_1&gt;, &lt;el_2&gt;, ...)
1249+
</code></pre>
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<h4 id="usefulbuiltinexceptions">Useful built-in exceptions:</h4>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">raise</span> ValueError(<span class="hljs-string">'Argument is of right type but inappropriate value!'</span>)
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<span class="hljs-keyword">raise</span> TypeError(<span class="hljs-string">'Argument is of wrong type!'</span>)
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<span class="hljs-keyword">raise</span> RuntimeError(<span class="hljs-string">'None of above!'</span>)
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</code></pre>
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<h4 id="reraisingcaughtexception">Re-raising caught exception:</h4>
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<pre><code class="python language-python hljs"><span class="hljs-keyword">except</span> &lt;exception&gt;:
1257+
&lt;code&gt;
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<span class="hljs-keyword">raise</span>
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</code></pre>
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<h3 id="commonbuiltinexceptions">Common Built-in Exceptions</h3>
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<pre><code class="python language-python hljs">BaseException
@@ -1255,9 +1279,13 @@ <h3 id="commonbuiltinexceptions">Common Built-in Exceptions</h3>
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+-- ValueError <span class="hljs-comment"># When an argument is of right type but inappropriate value.</span>
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+-- UnicodeError <span class="hljs-comment"># Raised when encoding/decoding strings from/to bytes fails. </span>
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</code></pre>
1258-
<ul>
1259-
<li><strong>Appropriate built-in exceptions for user to rise are: 'ValueError', 'TypeError' and 'RuntimeError'.</strong></li>
1260-
</ul>
1282+
<h3 id="userdefinedexceptions">User-defined Exceptions</h3>
1283+
<pre><code class="python language-python hljs"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">MyError</span><span class="hljs-params">(Exception)</span>:</span>
1284+
<span class="hljs-keyword">pass</span>
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<span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">MyInputError</span><span class="hljs-params">(MyError)</span>:</span>
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<span class="hljs-keyword">pass</span>
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</code></pre>
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<h2 id="print"><a href="#print" name="print">#</a>Print</h2>
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<pre><code class="python language-python hljs">print(&lt;el_1&gt;, ..., sep=<span class="hljs-string">' '</span>, end=<span class="hljs-string">'\n'</span>, file=sys.stdout, flush=<span class="hljs-keyword">False</span>)
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</code></pre>

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