Delay excel, probably broken

Author: TomAugspurger

pandas/core/config_init.py

@@ -458,13 +458,23 @@ def _register_xlsx(engine, other):
                                                     others=", '%s'" % other),
                            validator=str)
 
-    try:
-        # better memory footprint
-        import xlsxwriter  # noqa
-        _register_xlsx('xlsxwriter', 'openpyxl')
-    except ImportError:
-        # fallback
-        _register_xlsx('openpyxl', 'xlsxwriter')
+_excel_registered = False
+
+
+def _register_excel_engines():
+    global _excel_registered
+
+    if not _excel_registered:
+        with cf.config_prefix('io.excel'):
+            try:
+                # better memory footprint
+                import xlsxwriter  # noqa
+                _register_xlsx('xlsxwriter', 'openpyxl')
+            except ImportError:
+                # fallback
+                _register_xlsx('openpyxl', 'xlsxwriter')
+        _excel_registered = True
+
 
 # Set up the io.parquet specific configuration.
 parquet_engine_doc = """

pandas/io/common.py

@@ -19,13 +19,6 @@
 # gh-12665: Alias for now and remove later.
 CParserError = ParserError
 
-
-try:
-    from s3fs import S3File
-    need_text_wrapping = (BytesIO, S3File)
-except ImportError:
-    need_text_wrapping = (BytesIO,)
-
 # common NA values
 # no longer excluding inf representations
 # '1.#INF','-1.#INF', '1.#INF000000',
@@ -322,6 +315,11 @@ def _get_handle(path_or_buf, mode, encoding=None, compression=None,
     handles : list of file-like objects
         A list of file-like object that were openned in this function.
     """
+    try:
+        from s3fs import S3File
+        need_text_wrapping = (BytesIO, S3File)
+    except ImportError:
+        need_text_wrapping = (BytesIO,)
 
     handles = list()
     f = path_or_buf

pandas/io/excel.py

@@ -25,7 +25,7 @@
 import pandas._libs.json as json
 from pandas.compat import (map, zip, reduce, range, lrange, u, add_metaclass,
                            string_types, OrderedDict)
-from pandas.core import config
+from pandas.core import config, config_init
 from pandas.io.formats.printing import pprint_thing
 import pandas.compat as compat
 import pandas.compat.openpyxl_compat as openpyxl_compat
@@ -690,6 +690,8 @@ class ExcelWriter(object):
     # ExcelWriter.
     def __new__(cls, path, engine=None, **kwargs):
         # only switch class if generic(ExcelWriter)
+        config_init._register_excel_engines()
+
         if issubclass(cls, ExcelWriter):
             if engine is None:
                 if isinstance(path, string_types):