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python-cheatsheet
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Enum, exceptions

pull/52/head
Jure Šorn 4 years ago
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2 changed files with 36 additions and 18 deletions
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  1. 28
      README.md
  2. 26
      index.html

28
README.md
View File

@ -1180,7 +1180,7 @@ class MyOpen():
def __enter__(self): def __enter__(self):
self.file = open(self.filename) self.file = open(self.filename)
return self.file return self.file
def __exit__(self, exc_type, exc_value, traceback):
def __exit__(self, exc_type, exception, traceback):
self.file.close() self.file.close()
``` ```
@ -1329,13 +1329,13 @@ Cutlery = Enum('Cutlery', ['fork', 'knife', 'spoon'])
Cutlery = Enum('Cutlery', {'fork': 1, 'knife': 2, 'spoon': 3}) Cutlery = Enum('Cutlery', {'fork': 1, 'knife': 2, 'spoon': 3})
``` ```
#### Functions can not be values, so they must be wrapped:
#### User-defined functions can not be values, so they must be wrapped:
```python ```python
from functools import partial from functools import partial
LogicOp = Enum('LogicOp', {'AND': partial(lambda l, r: l and r), LogicOp = Enum('LogicOp', {'AND': partial(lambda l, r: l and r),
'OR' : partial(lambda l, r: l or r)}) 'OR' : partial(lambda l, r: l or r)})
``` ```
* **Another solution in this particular case, is to use `'and_'` and `'or_'` functions from module [operator](#operator).**
* **Another solution in this particular case is to use built-in functions `'and_'` and `'or_'` from the module [operator](#operator).**
Exceptions Exceptions
@ -1381,16 +1381,19 @@ raise <exception>(<el> [, ...])
#### Re-raising caught exception: #### Re-raising caught exception:
```python ```python
except <exception>:
<code>
except <exception> as <name>:
...
raise raise
``` ```
#### Useful built-in exceptions:
### Attributes
```python ```python
raise TypeError('Argument is of wrong type!')
raise ValueError('Argument is of right type but inappropriate value!')
raise RuntimeError('None of above!')
arguments = <name>.args
line_num = <name>.__traceback__.tb_lineno
func_name = <name>.__traceback__.tb_frame.f_code.co_name
filename = <name>.__traceback__.tb_frame.f_code.co_filename
line = linecache.getline(filename, line_num)
error_msg = traceback.format_exc()
``` ```
### Common Built-in Exceptions ### Common Built-in Exceptions
@ -1417,6 +1420,13 @@ BaseException
+-- UnicodeError # Raised when encoding/decoding strings from/to bytes fails. +-- UnicodeError # Raised when encoding/decoding strings from/to bytes fails.
``` ```
#### Useful built-in exceptions:
```python
raise TypeError('Argument is of wrong type!')
raise ValueError('Argument is of right type but inappropriate value!')
raise RuntimeError('None of above!')
```
#### Collections and their exceptions: #### Collections and their exceptions:
```text ```text
+-----------+------------+------------+------------+ +-----------+------------+------------+------------+

26
index.html
View File

@ -1123,7 +1123,7 @@ Z = dataclasses.make_dataclass(<span class="hljs-string">'Z'</span>, [<span clas
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__enter__</span><span class="hljs-params">(self)</span>:</span> <span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__enter__</span><span class="hljs-params">(self)</span>:</span>
self.file = open(self.filename) self.file = open(self.filename)
<span class="hljs-keyword">return</span> self.file <span class="hljs-keyword">return</span> self.file
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__exit__</span><span class="hljs-params">(self, exc_type, exc_value, traceback)</span>:</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__exit__</span><span class="hljs-params">(self, exc_type, exception, traceback)</span>:</span>
self.file.close() self.file.close()
</code></pre></div> </code></pre></div>
@ -1256,13 +1256,13 @@ Cutlery = Enum(<span class="hljs-string">'Cutlery'</span>, [<span class="hljs-st
Cutlery = Enum(<span class="hljs-string">'Cutlery'</span>, {<span class="hljs-string">'fork'</span>: <span class="hljs-number">1</span>, <span class="hljs-string">'knife'</span>: <span class="hljs-number">2</span>, <span class="hljs-string">'spoon'</span>: <span class="hljs-number">3</span>}) Cutlery = Enum(<span class="hljs-string">'Cutlery'</span>, {<span class="hljs-string">'fork'</span>: <span class="hljs-number">1</span>, <span class="hljs-string">'knife'</span>: <span class="hljs-number">2</span>, <span class="hljs-string">'spoon'</span>: <span class="hljs-number">3</span>})
</code></pre></div> </code></pre></div>
<div><h4 id="functionscannotbevaluessotheymustbewrapped">Functions can not be values, so they must be wrapped:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> functools <span class="hljs-keyword">import</span> partial
<div><h4 id="userdefinedfunctionscannotbevaluessotheymustbewrapped">User-defined functions can not be values, so they must be wrapped:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> functools <span class="hljs-keyword">import</span> partial
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), 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),
<span class="hljs-string">'OR'</span> : partial(<span class="hljs-keyword">lambda</span> l, r: l <span class="hljs-keyword">or</span> r)}) <span class="hljs-string">'OR'</span> : partial(<span class="hljs-keyword">lambda</span> l, r: l <span class="hljs-keyword">or</span> r)})
</code></pre></div> </code></pre></div>
<ul> <ul>
<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>.</strong></li>
<li><strong>Another solution in this particular case is to use built-in functions <code class="python hljs"><span class="hljs-string">'and_'</span></code> and <code class="python hljs"><span class="hljs-string">'or_'</span></code> from the module <a href="#operator">operator</a>.</strong></li>
</ul> </ul>
<div><h2 id="exceptions"><a href="#exceptions" name="exceptions">#</a>Exceptions</h2><div><h3 id="basicexample">Basic Example</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">try</span>: <div><h2 id="exceptions"><a href="#exceptions" name="exceptions">#</a>Exceptions</h2><div><h3 id="basicexample">Basic Example</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">try</span>:
&lt;code&gt; &lt;code&gt;
@ -1297,14 +1297,17 @@ LogicOp = Enum(<span class="hljs-string">'LogicOp'</span>, {<span class="hljs-st
<span class="hljs-keyword">raise</span> &lt;exception&gt;(&lt;el&gt; [, ...]) <span class="hljs-keyword">raise</span> &lt;exception&gt;(&lt;el&gt; [, ...])
</code></pre></div> </code></pre></div>
<div><h4 id="reraisingcaughtexception">Re-raising caught exception:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">except</span> &lt;exception&gt;:
&lt;code&gt;
<div><h4 id="reraisingcaughtexception">Re-raising caught exception:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">except</span> &lt;exception&gt; <span class="hljs-keyword">as</span> &lt;name&gt;:
...
<span class="hljs-keyword">raise</span> <span class="hljs-keyword">raise</span>
</code></pre></div> </code></pre></div>
<div><h4 id="usefulbuiltinexceptions">Useful built-in exceptions:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">raise</span> TypeError(<span class="hljs-string">'Argument is of wrong type!'</span>)
<span class="hljs-keyword">raise</span> ValueError(<span class="hljs-string">'Argument is of right type but inappropriate value!'</span>)
<span class="hljs-keyword">raise</span> RuntimeError(<span class="hljs-string">'None of above!'</span>)
<div><h3 id="attributes-1">Attributes</h3><pre><code class="python language-python hljs">arguments = &lt;name&gt;.args
line_num = &lt;name&gt;.__traceback__.tb_lineno
func_name = &lt;name&gt;.__traceback__.tb_frame.f_code.co_name
filename = &lt;name&gt;.__traceback__.tb_frame.f_code.co_filename
line = linecache.getline(filename, line_num)
error_msg = traceback.format_exc()
</code></pre></div> </code></pre></div>
<div><h3 id="commonbuiltinexceptions">Common Built-in Exceptions</h3><pre><code class="text language-text">BaseException <div><h3 id="commonbuiltinexceptions">Common Built-in Exceptions</h3><pre><code class="text language-text">BaseException
@ -1329,6 +1332,11 @@ LogicOp = Enum(<span class="hljs-string">'LogicOp'</span>, {<span class="hljs-st
+-- UnicodeError # Raised when encoding/decoding strings from/to bytes fails. +-- UnicodeError # Raised when encoding/decoding strings from/to bytes fails.
</code></pre></div> </code></pre></div>
<div><h4 id="usefulbuiltinexceptions">Useful built-in exceptions:</h4><pre><code class="python language-python hljs"><span class="hljs-keyword">raise</span> TypeError(<span class="hljs-string">'Argument is of wrong type!'</span>)
<span class="hljs-keyword">raise</span> ValueError(<span class="hljs-string">'Argument is of right type but inappropriate value!'</span>)
<span class="hljs-keyword">raise</span> RuntimeError(<span class="hljs-string">'None of above!'</span>)
</code></pre></div>
<div><h4 id="collectionsandtheirexceptions">Collections and their exceptions:</h4><pre><code class="text language-text">+-----------+------------+------------+------------+ <div><h4 id="collectionsandtheirexceptions">Collections and their exceptions:</h4><pre><code class="text language-text">+-----------+------------+------------+------------+
| | list | dict | set | | | list | dict | set |
+-----------+------------+------------+------------+ +-----------+------------+------------+------------+
@ -1854,7 +1862,7 @@ last_el = op.methodcaller(<span class="hljs-string">'pop'</span>)(&lt;l
<div><h3 id="attributes-1">Attributes</h3><pre><code class="python language-python hljs">&lt;list&gt; = dir(&lt;object&gt;) <span class="hljs-comment"># Returns names of object's attributes (incl. methods).</span>
<div><h3 id="attributes-2">Attributes</h3><pre><code class="python language-python hljs">&lt;list&gt; = dir(&lt;object&gt;) <span class="hljs-comment"># Returns names of object's attributes (incl. methods).</span>
&lt;dict&gt; = vars(&lt;object&gt;) <span class="hljs-comment"># Returns dict of object's fields. Also &lt;object&gt;.__dict__.</span> &lt;dict&gt; = vars(&lt;object&gt;) <span class="hljs-comment"># Returns dict of object's fields. Also &lt;object&gt;.__dict__.</span>
</code></pre></div> </code></pre></div>

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