Type and metaclasses

gto76 · gto76 · commit 69e31bb94cc4 · 2019-04-04T01:51:15.000+02:00
diff --git a/README.md b/README.md
@@ -226,17 +226,42 @@ def count(start, step):
 
 Type
 ----
+* **Everything is an object.**
+* **Every object has a type.**
+* **Type and class are synonymous.**
+
+```python
+<type>  = type(<el>)                      # Or: <type> = <el>.__class__
+<bool>  = isinstance(<el>, <type>)        # Also true if 'type' is a superclass of el's type.
+```
+
+```python
+<tuple> = <type>.__bases__                # A tuple of type's parents.
+<list>  = <type>.mro()                    # Returns a list of all type's superclasses.
+<bool>  = issubclass(<sub_type>, <type>)  # Checks if 'sub_type' is a subclass of 'type'.
+```
+
+* **Every class is a subclass and a superclass of itself.**
+
 ```python
-<type> = type(<el>)  # <class 'int'> / <class 'str'> / ...
+>>> type('a'), 'a'.__class__, str
+(<class 'str'>, <class 'str'>, <class 'str'>)
 ```
 
+#### Some types do not have builtin names, so they must be imported:
+```python
+from types import FunctionType, MethodType, LambdaType, GeneratorType
+```
+
+### ABC-s
 ```python
 from numbers import Integral, Rational, Real, Complex, Number
 <bool> = isinstance(<el>, Number)
 ```
 
 ```python
-<bool> = callable(<el>)
+from collections.abc import Iterable, Collection, Sequence
+<bool> = isinstance(<el>, Iterable)
 ```
 
 
@@ -1514,6 +1539,32 @@ class MyClass(metaclass=MyMetaClass):
 ('abcde', 12345)
 ```
 
+#### Type diagram ('abc' is a str, str is a type, ...):
+```text
+┏━━━━━━━━━┯━━━━━━━━━━━━━┓
+┃ classes │ metaclasses ┃
+┠─────────┼─────────────┨
+┃ MyClass → MyMetaClass ┃
+┃         │     ↓       ┃
+┃  object ───→ type ←╮  ┃
+┃         │    ↑ ╰───╯  ┃
+┃   str ───────╯        ┃
+┗━━━━━━━━━┷━━━━━━━━━━━━━┛
+```
+
+#### Inheritance diagram (str inherits from object, ...):
+```text
+┏━━━━━━━━━┯━━━━━━━━━━━━━┓
+┃ classes │ metaclasses ┃
+┠─────────┼─────────────┨
+┃ MyClass │ MyMetaClass ┃
+┃    ↓    │     ↓       ┃
+┃  object ←─── type     ┃
+┃    ↑    │             ┃
+┃   str   │             ┃
+┗━━━━━━━━━┷━━━━━━━━━━━━━┛
+```
+
 
 Operator
 --------
diff --git a/index.html b/index.html
@@ -302,12 +302,33 @@ <h2 id="generator"><a href="#generator" name="generator">#</a>Generator</h2>
 (<span class="hljs-number">10</span>, <span class="hljs-number">12</span>, <span class="hljs-number">14</span>)
 </code></pre>
 <h2 id="type"><a href="#type" name="type">#</a>Type</h2>
-<pre><code class="python language-python hljs">&lt;type&gt; = type(&lt;el&gt;)  <span class="hljs-comment"># &lt;class 'int'&gt; / &lt;class 'str'&gt; / ...</span>
+<ul>
+<li><strong>Everything is an object.</strong></li>
+<li><strong>Every object has a type.</strong></li>
+<li><strong>Type and class are synonymous.</strong></li>
+</ul>
+<pre><code class="python language-python hljs">&lt;type&gt;  = type(&lt;el&gt;)                      <span class="hljs-comment"># Or: &lt;type&gt; = &lt;el&gt;.__class__</span>
+&lt;bool&gt;  = isinstance(&lt;el&gt;, &lt;type&gt;)        <span class="hljs-comment"># Also true if 'type' is a superclass of el's type.</span>
+</code></pre>
+<pre><code class="python language-python hljs">&lt;tuple&gt; = &lt;type&gt;.__bases__                <span class="hljs-comment"># A tuple of type's parents.</span>
+&lt;list&gt;  = &lt;type&gt;.mro()                    <span class="hljs-comment"># Returns a list of all type's superclasses.</span>
+&lt;bool&gt;  = issubclass(&lt;sub_type&gt;, &lt;type&gt;)  <span class="hljs-comment"># Checks if 'sub_type' is a subclass of 'type'.</span>
+</code></pre>
+<ul>
+<li><strong>Every class is a subclass and a superclass of itself.</strong></li>
+</ul>
+<pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>type(<span class="hljs-string">'a'</span>), <span class="hljs-string">'a'</span>.__class__, str
+(&lt;<span class="hljs-class"><span class="hljs-keyword">class</span> '<span class="hljs-title">str</span>'&gt;, &lt;<span class="hljs-title">class</span> '<span class="hljs-title">str</span>'&gt;, &lt;<span class="hljs-title">class</span> '<span class="hljs-title">str</span>'&gt;)
+</span></code></pre>
+<h4 id="sometypesdonothavebuiltinnamessotheymustbeimported">Some types do not have builtin names, so they must be imported:</h4>
+<pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> types <span class="hljs-keyword">import</span> FunctionType, MethodType, LambdaType, GeneratorType
 </code></pre>
+<h3 id="abcs">ABC-s</h3>
 <pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> numbers <span class="hljs-keyword">import</span> Integral, Rational, Real, Complex, Number
 &lt;bool&gt; = isinstance(&lt;el&gt;, Number)
 </code></pre>
-<pre><code class="python language-python hljs">&lt;bool&gt; = callable(&lt;el&gt;)
+<pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> collections.abc <span class="hljs-keyword">import</span> Iterable, Collection, Sequence
+&lt;bool&gt; = isinstance(&lt;el&gt;, Iterable)
 </code></pre>
 <h2 id="string"><a href="#string" name="string">#</a>String</h2>
 <pre><code class="python language-python hljs">&lt;str&gt;  = &lt;str&gt;.strip()                       <span class="hljs-comment"># Strips all whitespace characters from both ends.</span>
@@ -1244,6 +1265,28 @@ <h3 id="metaclassattribute">Metaclass Attribute</h3>
 <pre><code class="python language-python hljs"><span class="hljs-meta">&gt;&gt;&gt; </span>MyClass.a, MyClass.b
 (<span class="hljs-string">'abcde'</span>, <span class="hljs-number">12345</span>)
 </code></pre>
+<h4 id="typediagramabcisastrstrisatype">Type diagram ('abc' is a str, str is a type, …):</h4>
+<pre><code class="text language-text">┏━━━━━━━━━┯━━━━━━━━━━━━━┓
+┃ classes │ metaclasses ┃
+┠─────────┼─────────────┨
+┃ MyClass → MyMetaClass ┃
+┃         │     ↓       ┃
+┃  object ───→ type ←╮  ┃
+┃         │    ↑ ╰───╯  ┃
+┃   str ───────╯        ┃
+┗━━━━━━━━━┷━━━━━━━━━━━━━┛
+</code></pre>
+<h4 id="inheritancediagramstrinheritsfromobject">Inheritance diagram (str inherits from object, …):</h4>
+<pre><code class="text language-text">┏━━━━━━━━━┯━━━━━━━━━━━━━┓
+┃ classes │ metaclasses ┃
+┠─────────┼─────────────┨
+┃ MyClass │ MyMetaClass ┃
+┃    ↓    │     ↓       ┃
+┃  object ←─── type     ┃
+┃    ↑    │             ┃
+┃   str   │             ┃
+┗━━━━━━━━━┷━━━━━━━━━━━━━┛
+</code></pre>
 <h2 id="operator"><a href="#operator" name="operator">#</a>Operator</h2>
 <pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> operator <span class="hljs-keyword">import</span> add, sub, mul, truediv, floordiv, mod, pow, neg, abs
 <span class="hljs-keyword">from</span> operator <span class="hljs-keyword">import</span> eq, ne, lt, le, gt, ge
