Python Enum patterns for status fields

<p>Using string literals for status values ('pending', 'validated', 'active') spread across the codebase. Typos cause silent bugs, IDEs can't autocomplete, and it's hard to find all places a status value is used.</p>

<p>Use Python Enum (or StrEnum) for type-safe status values:</p> <div class="highlight"><pre><span></span><code><span class="kn">from</span><span class="w"> </span><span class="nn">enum</span><span class="w"> </span><span class="kn">import</span> <span class="n">Enum</span><span class="p">,</span> <span class="n">StrEnum</span> <span class="c1"># StrEnum (Python 3.11+) — inherits from str, works in string contexts</span> <span class="k">class</span><span class="w"> </span><span class="nc">TraceStatus</span><span class="p">(</span><span class="n">StrEnum</span><span class="p">):</span> <span class="n">pending</span> <span class="o">=</span> <span class="s1">'pending'</span> <span class="n">validated</span> <span class="o">=</span> <span class="s1">'validated'</span> <span class="c1"># Older Python — use str mixin</span> <span class="k">class</span><span class="w"> </span><span class="nc">TraceStatus</span><span class="p">(</span><span class="nb">str</span><span class="p">,</span> <span class="n">Enum</span><span class="p">):</span> <span class="n">pending</span> <span class="o">=</span> <span class="s1">'pending'</span> <span class="n">validated</span> <span class="o">=</span> <span class="s1">'validated'</span> <span class="c1"># Usage</span> <span class="n">status</span> <span class="o">=</span> <span class="n">TraceStatus</span><span class="o">.</span><span class="n">pending</span> <span class="nb">print</span><span class="p">(</span><span class="n">status</span> <span class="o">==</span> <span class="s1">'pending'</span><span class="p">)</span> <span class="c1"># True — compares as string</span> <span class="nb">print</span><span class="p">(</span><span class="n">status</span><span class="o">.</span><span class="n">value</span><span class="p">)</span> <span class="c1"># 'pending'</span> <span class="nb">print</span><span class="p">(</span><span class="nb">str</span><span class="p">(</span><span class="n">status</span><span class="p">))</span> <span class="c1"># 'pending'</span> <span class="c1"># SQLAlchemy: store as string, load as enum</span> <span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy</span><span class="w"> </span><span class="kn">import</span> <span class="n">String</span> <span class="kn">from</span><span class="w"> </span><span class="nn">sqlalchemy.orm</span><span class="w"> </span><span class="kn">import</span> <span class="n">mapped_column</span><span class="p">,</span> <span class="n">Mapped</span> <span class="k">class</span><span class="w"> </span><span class="nc">Trace</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span> <span class="n">status</span><span class="p">:</span> <span class="n">Mapped</span><span class="p">[</span><span class="nb">str</span><span class="p">]</span> <span class="o">=</span> <span class="n">mapped_column</span><span class="p">(</span> <span class="n">String</span><span class="p">(</span><span class="mi">20</span><span class="p">),</span> <span class="n">default</span><span class="o">=</span><span class="n">TraceStatus</span><span class="o">.</span><span class="n">pending</span> <span class="p">)</span> <span class="c1"># Pydantic: validate string input as enum</span> <span class="kn">from</span><span class="w"> </span><span class="nn">pydantic</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseModel</span> <span class="k">class</span><span class="w"> </span><span class="nc">TraceCreate</span><span class="p">(</span><span class="n">BaseModel</span><span class="p">):</span> <span class="n">status</span><span class="p">:</span> <span class="n">TraceStatus</span> <span class="o">=</span> <span class="n">TraceStatus</span><span class="o">.</span><span class="n">pending</span> <span class="n">request</span> <span class="o">=</span> <span class="n">TraceCreate</span><span class="p">(</span><span class="n">status</span><span class="o">=</span><span class="s1">'validated'</span><span class="p">)</span> <span class="c1"># Works</span> <span class="n">request</span> <span class="o">=</span> <span class="n">TraceCreate</span><span class="p">(</span><span class="n">status</span><span class="o">=</span><span class="s1">'invalid'</span><span class="p">)</span> <span class="c1"># ValidationError</span> <span class="c1"># Pattern matching with enum</span> <span class="k">def</span><span class="w"> </span><span class="nf">handle_trace</span><span class="p">(</span><span class="n">status</span><span class="p">:</span> <span class="n">TraceStatus</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">str</span><span class="p">:</span> <span class="k">match</span> <span class="n">status</span><span class="p">:</span> <span class="k">case</span> <span class="n">TraceStatus</span><span class="o">.</span><span class="n">pending</span><span class="p">:</span> <span class="k">return</span> <span class="s1">'Waiting for votes'</span> <span class="k">case</span> <span class="n">TraceStatus</span><span class="o">.</span><span class="n">validated</span><span class="p">:</span> <span class="k">return</span> <span class="s1">'Accepted by community'</span> <span class="k">case</span><span class="w"> </span><span class="k">_</span><span class="p">:</span> <span class="k">return</span> <span class="s1">'Unknown status'</span> <span class="c1"># Enum with additional properties</span> <span class="k">class</span><span class="w"> </span><span class="nc">Priority</span><span class="p">(</span><span class="n">Enum</span><span class="p">):</span> <span class="n">low</span> <span class="o">=</span> <span class="mi">1</span> <span class="n">medium</span> <span class="o">=</span> <span class="mi">2</span> <span class="n">high</span> <span class="o">=</span> <span class="mi">3</span> <span class="n">critical</span> <span class="o">=</span> <span class="mi">4</span> <span class="nd">@property</span> <span class="k">def</span><span class="w"> </span><span class="nf">is_urgent</span><span class="p">(</span><span class="bp">self</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">bool</span><span class="p">:</span> <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">value</span> <span class="o">&gt;=</span> <span class="mi">3</span> <span class="k">def</span><span class="w"> </span><span class="fm">__lt__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">other</span><span class="p">:</span> <span class="s1">'Priority'</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="nb">bool</span><span class="p">:</span> <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">value</span> <span class="o">&lt;</span> <span class="n">other</span><span class="o">.</span><span class="n">value</span> </code></pre></div> <p><code>StrEnum</code> values compare equal to their string representation — safe to use in f-strings, dict keys, and JSON without <code>.value</code>. Add enum values to <code>__all__</code> in the module so they're importable at the top level.</p>