Bugfix handle edge case when we have string in list and want to flatten

fastcore/basics.py

@@ -489,6 +489,7 @@ class Float(float,ShowPrint):
 def flatten(o):
     "Concatenate all collections and items as a generator"
     for item in o:
+        if isinstance(item, str): yield item; continue
         try: yield from flatten(item)
         except TypeError: yield item
 

nbs/01_basics.ipynb

@@ -2904,6 +2904,7 @@
     "def flatten(o):\n",
     "    \"Concatenate all collections and items as a generator\"\n",
     "    for item in o:\n",
+    "        if isinstance(item, str): yield item; continue\n",
     "        try: yield from flatten(item)\n",
     "        except TypeError: yield item"
    ]
@@ -2940,6 +2941,26 @@
     "concat([(o for o in range(2)),[2,3,4], 5])"
    ]
   },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "['abc', 'xyz', 'foo', 'bar']"
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "concat([[\"abc\", \"xyz\"], [\"foo\", \"bar\"]])"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
@@ -5306,7 +5327,7 @@
     {
      "data": {
       "text/plain": [
-       "64"
+       "8"
       ]
      },
      "execution_count": null,