BUG: Improved thread safety for read_html() GH16928

Author: 3553x

doc/source/whatsnew/v0.21.0.txt

@@ -164,6 +164,8 @@ I/O
 
 - Bug in :func:`read_stata` where value labels could not be read when using an iterator (:issue:`16923`)
 
+- Bug in :func:`read_html` importcheck fails when run concurrently (:issue:`16928`)
+
 Plotting
 ^^^^^^^^
 - Bug in plotting methods using ``secondary_y`` and ``fontsize`` not setting secondary axis font size (:issue:`12565`)

pandas/io/html.py

@@ -37,8 +37,6 @@ def _importers():
     if _IMPORTS:
         return
 
-    _IMPORTS = True
-
     global _HAS_BS4, _HAS_LXML, _HAS_HTML5LIB
 
     try:
@@ -59,6 +57,8 @@ def _importers():
     except ImportError:
         pass
 
+    _IMPORTS = True
+
 
 #############
 # READ HTML #