richard
/
python-cheatsheet
mirror of https://github.com/gto76/python-cheatsheet.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
Browse Source

Introspection

pull/46/head
Jure Šorn 5 years ago
parent
e5a6aa40a9
commit
e48a865d00
2 changed files with 38 additions and 33 deletions
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 31
      README.md
  2. 40
      index.html

31
README.md
View File

@ -1302,11 +1302,11 @@ class <enum_name>(Enum):
* **Otherwise it returns an increment of the last numeric value.**
```python
<member> = <enum>.<member_name> # Returns a member.
<member> = <enum>['<member_name>'] # Returns a member or raises KeyError.
<member> = <enum>(<value>) # Returns a member or raises ValueError.
<str> = <member>.name # Returns member's name.
<obj> = <member>.value # Returns member's value.
<member> = <enum>.<member_name> # Returns a member.
<member> = <enum>['<member_name>'] # Returns a member or raises KeyError.
<member> = <enum>(<value>) # Returns a member or raises ValueError.
<str> = <member>.name # Returns member's name.
<obj> = <member>.value # Returns member's value.
```
```python
@ -1992,9 +1992,6 @@ Deque
```python
from collections import deque
<deque> = deque(<collection>, maxlen=None)
```
```python
<deque>.appendleft(<el>) # Opposite element is dropped if full.
<el> = <deque>.popleft() # Raises IndexError if empty.
<deque>.extendleft(<collection>) # Collection gets reversed.
@ -2092,19 +2089,25 @@ Introspection
### Variables
```python
<list> = dir() # Returns names of variables in current scope.
<dict> = locals() # Returns dict of local variables. Also vars().
<list> = dir() # Returns names of local variables (including functions).
<dict> = vars() # Returns dict of local variables. Also locals().
<dict> = globals() # Returns dict of global variables.
```
### Attributes
```python
<dict> = vars(<object>)
<list> = dir(<object>) # Returns names of object's attributes (incl. methods).
<dict> = vars(<object>) # Returns dict of object's fields. Also <object>.__dict__.
```
```python
<bool> = hasattr(<object>, '<attr_name>')
value = getattr(<object>, '<attr_name>')
setattr(<object>, '<attr_name>', value)
delattr(<object>, '<attr_name>')
```
### Parameters
```python
from inspect import signature
@ -2648,9 +2651,9 @@ from PIL import Image
```
```bash
<2d_array> = np.array(<Image>) # NumPy array from greyscale image.
<3d_array> = np.array(<Image>) # NumPy array from color image.
<Image> = Image.fromarray(<array>) # Image from NumPy array.
<2d_array> = np.array(<Image>) # Generates NumPy array from greyscale image.
<3d_array> = np.array(<Image>) # Generates NumPy array from color image.
<Image> = Image.fromarray(<array>) # Generates image from NumPy array.
```
### Modes

40
index.html
View File

@ -1234,11 +1234,11 @@ Hello World!
<li><strong>If there are no numeric values before auto(), it returns 1.</strong></li>
<li><strong>Otherwise it returns an increment of the last numeric value.</strong></li>
</ul>
<pre><code class="python language-python hljs">&lt;member&gt; = &lt;enum&gt;.&lt;member_name&gt; <span class="hljs-comment"># Returns a member.</span>
&lt;member&gt; = &lt;enum&gt;[<span class="hljs-string">'&lt;member_name&gt;'</span>] <span class="hljs-comment"># Returns a member or raises KeyError.</span>
&lt;member&gt; = &lt;enum&gt;(&lt;value&gt;) <span class="hljs-comment"># Returns a member or raises ValueError.</span>
&lt;str&gt; = &lt;member&gt;.name <span class="hljs-comment"># Returns member's name.</span>
&lt;obj&gt; = &lt;member&gt;.value <span class="hljs-comment"># Returns member's value.</span>
<pre><code class="python language-python hljs">&lt;member&gt; = &lt;enum&gt;.&lt;member_name&gt; <span class="hljs-comment"># Returns a member.</span>
&lt;member&gt; = &lt;enum&gt;[<span class="hljs-string">'&lt;member_name&gt;'</span>] <span class="hljs-comment"># Returns a member or raises KeyError.</span>
&lt;member&gt; = &lt;enum&gt;(&lt;value&gt;) <span class="hljs-comment"># Returns a member or raises ValueError.</span>
&lt;str&gt; = &lt;member&gt;.name <span class="hljs-comment"># Returns member's name.</span>
&lt;obj&gt; = &lt;member&gt;.value <span class="hljs-comment"># Returns member's value.</span>
</code></pre>
<pre><code class="python language-python hljs">list_of_members = list(&lt;enum&gt;)
member_names = [a.name <span class="hljs-keyword">for</span> a <span class="hljs-keyword">in</span> &lt;enum&gt;]
@ -1761,14 +1761,13 @@ db = connector.connect(host=&lt;str&gt;, user=&lt;str&gt;, password=&lt;str&gt;,
<div><h2 id="deque"><a href="#deque" name="deque">#</a>Deque</h2><p><strong>A thread-safe list with efficient appends and pops from either side. Pronounced "deck".</strong></p><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> collections <span class="hljs-keyword">import</span> deque
&lt;deque&gt; = deque(&lt;collection&gt;, maxlen=<span class="hljs-keyword">None</span>)
</code></pre></div>
<pre><code class="python language-python hljs">&lt;deque&gt;.appendleft(&lt;el&gt;) <span class="hljs-comment"># Opposite element is dropped if full.</span>
&lt;deque&gt;.appendleft(&lt;el&gt;) <span class="hljs-comment"># Opposite element is dropped if full.</span>
&lt;el&gt; = &lt;deque&gt;.popleft() <span class="hljs-comment"># Raises IndexError if empty.</span>
&lt;deque&gt;.extendleft(&lt;collection&gt;) <span class="hljs-comment"># Collection gets reversed.</span>
&lt;deque&gt;.rotate(n=<span class="hljs-number">1</span>) <span class="hljs-comment"># Rotates elements to the right.</span>
</code></pre>
</code></pre></div>
<div><h2 id="threading"><a href="#threading" name="threading">#</a>Threading</h2><ul>
<li><strong>CPython interpreter can only run a single thread at a time.</strong></li>
<li><strong>That is why using multiple threads won't result in a faster execution, unless there is an I/O operation in the thread.</strong></li>
@ -1833,19 +1832,22 @@ product_of_elems = functools.reduce(op.mul, &lt;collection&gt;)
LogicOp = enum.Enum(<span class="hljs-string">'LogicOp'</span>, {<span class="hljs-string">'AND'</span>: op.and_, <span class="hljs-string">'OR'</span> : op.or_})
last_el = op.methodcaller(<span class="hljs-string">'pop'</span>)(&lt;list&gt;)
</code></pre>
<div><h2 id="introspection"><a href="#introspection" name="introspection">#</a>Introspection</h2><p><strong>Inspecting code at runtime.</strong></p><div><h3 id="variables">Variables</h3><pre><code class="python language-python hljs">&lt;list&gt; = dir() <span class="hljs-comment"># Returns names of variables in current scope.</span>
&lt;dict&gt; = locals() <span class="hljs-comment"># Returns dict of local variables. Also vars().</span>
<div><h2 id="introspection"><a href="#introspection" name="introspection">#</a>Introspection</h2><p><strong>Inspecting code at runtime.</strong></p><div><h3 id="variables">Variables</h3><pre><code class="python language-python hljs">&lt;list&gt; = dir() <span class="hljs-comment"># Returns names of local variables (including functions).</span>
&lt;dict&gt; = vars() <span class="hljs-comment"># Returns dict of local variables. Also locals().</span>
&lt;dict&gt; = globals() <span class="hljs-comment"># Returns dict of global variables.</span>
</code></pre></div></div>
<div><h3 id="attributes-1">Attributes</h3><pre><code class="python language-python hljs">&lt;dict&gt; = vars(&lt;object&gt;)
&lt;bool&gt; = hasattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)
value = getattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)
setattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>, value)
<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>
&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>
<pre><code class="python language-python hljs">&lt;bool&gt; = hasattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)
value = getattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)
setattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>, value)
delattr(&lt;object&gt;, <span class="hljs-string">'&lt;attr_name&gt;'</span>)
</code></pre>
<div><h3 id="parameters-1">Parameters</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> inspect <span class="hljs-keyword">import</span> signature
&lt;sig&gt; = signature(&lt;function&gt;)
no_of_params = len(&lt;sig&gt;.parameters)
@ -2257,9 +2259,9 @@ right = [[<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</s
&lt;Image&gt;.putdata(&lt;list/ImagingCore&gt;) <span class="hljs-comment"># Writes a sequence of pixels.</span>
&lt;Image&gt;.paste(&lt;Image&gt;, (x, y)) <span class="hljs-comment"># Writes an image to image.</span>
</code></pre>
<pre><code class="bash language-bash hljs">&lt;2d_array&gt; = np.array(&lt;Image&gt;) <span class="hljs-comment"># NumPy array from greyscale image.</span>
&lt;3d_array&gt; = np.array(&lt;Image&gt;) <span class="hljs-comment"># NumPy array from color image.</span>
&lt;Image&gt; = Image.fromarray(&lt;array&gt;) <span class="hljs-comment"># Image from NumPy array.</span>
<pre><code class="bash language-bash hljs">&lt;2d_array&gt; = np.array(&lt;Image&gt;) <span class="hljs-comment"># Generates NumPy array from greyscale image.</span>
&lt;3d_array&gt; = np.array(&lt;Image&gt;) <span class="hljs-comment"># Generates NumPy array from color image.</span>
&lt;Image&gt; = Image.fromarray(&lt;array&gt;) <span class="hljs-comment"># Generates image from NumPy array.</span>
</code></pre>
<div><h3 id="modes-1">Modes</h3><ul>
<li><strong><code class="python hljs"><span class="hljs-string">'1'</span></code> - 1-bit pixels, black and white, stored with one pixel per byte.</strong></li>

Write Preview
Loading…
Cancel
Save