Update sqlite3-python/README.md

sqlite3-python/README.md

@@ -22,6 +22,33 @@ print(sql[4]) # 2
 print(list(sql)) # [4]
 ```
 
+# Cache
+```python
+class SQL:
+    def __init__(self):
+        import sqlite3
+        con = sqlite3.connect('fetch.db', isolation_level=None, timeout=1e999)
+        con.row_factory = sqlite3.Row
+        self.execute = con.execute
+        self('PRAGMA busy_timeout='f'{1e9}')
+        self('PRAGMA journal_mode=WAL')
+        self('PRAGMA wal_checkpoint(FULL)')
+        self('CREATE TABLE IF NOT EXISTS cache(url TEXT PRIMARY KEY, blob BLOB)')
+    def __call__(self, q, *p): return list(map(dict, self.execute(q, p)))
+    def __setitem__(self, url, blob): self('INSERT OR REPLACE INTO cache VALUES(?,?)', url, blob)
+    def __getitem__(self, url): 
+        if blob := self('SELECT blob FROM cache WHERE url=?', url): return blob[0]['blob']
+    def __delitem__(self, url): self('DELETE FROM cache WHERE url=?', url)
+    def __iter__(self): return iter(url['url'] for url in self('SELECT url FROM cache'))
+    def fetch(self, url):
+        import urllib.request
+        if not (blob := self[url]): self[url] = urllib.request.urlopen(url).read()
+        return self[url]
+sql = SQL()
+sql.fetch('https://example.com')
+list(sql)
+```
+
 # Class
 ```python
 class SQL: