From ff9fc5bd69d2766c6b592585b5b9eb422950f3cd Mon Sep 17 00:00:00 2001
From: willbowditch <14288042+willbowditch@users.noreply.github.com>
Date: Tue, 7 Jul 2020 18:16:07 +0100
Subject: [PATCH 1/4] Infer compression even if file extension is uppercase

---
 pandas/io/common.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index 51323c5ff3ef5..4e6395fc67b2a 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -311,7 +311,7 @@ def infer_compression(
 
         # Infer compression from the filename/URL extension
         for compression, extension in _compression_to_extension.items():
-            if filepath_or_buffer.endswith(extension):
+            if filepath_or_buffer.lower().endswith(extension):
                 return compression
         return None
 

From 6f75ac5dab51c7505455acbafa232c4ee387c5c4 Mon Sep 17 00:00:00 2001
From: willbowditch <14288042+willbowditch@users.noreply.github.com>
Date: Tue, 7 Jul 2020 18:28:19 +0100
Subject: [PATCH 2/4] Add upercase extensions to infer compression tests

---
 pandas/tests/io/test_common.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/pandas/tests/io/test_common.py b/pandas/tests/io/test_common.py
index e2f4ae04c1f9f..dde38eb55ea7f 100644
--- a/pandas/tests/io/test_common.py
+++ b/pandas/tests/io/test_common.py
@@ -87,7 +87,17 @@ def test_stringify_path_fspath(self):
 
     @pytest.mark.parametrize(
         "extension,expected",
-        [("", None), (".gz", "gzip"), (".bz2", "bz2"), (".zip", "zip"), (".xz", "xz")],
+        [
+            ("", None),
+            (".gz", "gzip"),
+            (".bz2", "bz2"),
+            (".zip", "zip"),
+            (".xz", "xz"),
+            (".GZ", "gzip"),
+            (".BZ2", "bz2"),
+            (".ZIP", "zip"),
+            (".XZ", "xz"),
+        ],
     )
     @pytest.mark.parametrize("path_type", path_types)
     def test_infer_compression_from_path(self, extension, expected, path_type):

From 6e2cd6d4809d3569e03897b36f741c723d43f67f Mon Sep 17 00:00:00 2001
From: willbowditch <14288042+willbowditch@users.noreply.github.com>
Date: Tue, 7 Jul 2020 18:40:34 +0100
Subject: [PATCH 3/4] Update whatsnew

---
 doc/source/whatsnew/v1.1.0.rst | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v1.1.0.rst b/doc/source/whatsnew/v1.1.0.rst
index cee41f248fc60..9cbc5bd6325ed 100644
--- a/doc/source/whatsnew/v1.1.0.rst
+++ b/doc/source/whatsnew/v1.1.0.rst
@@ -1050,6 +1050,7 @@ I/O
 - Bug in :meth:`~HDFStore.create_table` now raises an error when `column` argument was not specified in `data_columns` on input (:issue:`28156`)
 - :meth:`read_json` now could read line-delimited json file from a file url while `lines` and `chunksize` are set.
 - Bug in :meth:`DataFrame.to_sql` when reading DataFrames with ``-np.inf`` entries with MySQL now has a more explicit ``ValueError`` (:issue:`34431`)
+- Bug in :meth:`io.common.infer_compression` where capitalised files extensions were not decompressed by read_* functions.
 
 Plotting
 ^^^^^^^^

From a3558fd33ac0aa34e964b9a048d23f814778b98a Mon Sep 17 00:00:00 2001
From: willbowditch <14288042+willbowditch@users.noreply.github.com>
Date: Fri, 10 Jul 2020 18:37:06 +0100
Subject: [PATCH 4/4] Add PR number

---
 doc/source/whatsnew/v1.1.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v1.1.0.rst b/doc/source/whatsnew/v1.1.0.rst
index 9cbc5bd6325ed..8f07951de4256 100644
--- a/doc/source/whatsnew/v1.1.0.rst
+++ b/doc/source/whatsnew/v1.1.0.rst
@@ -1050,7 +1050,7 @@ I/O
 - Bug in :meth:`~HDFStore.create_table` now raises an error when `column` argument was not specified in `data_columns` on input (:issue:`28156`)
 - :meth:`read_json` now could read line-delimited json file from a file url while `lines` and `chunksize` are set.
 - Bug in :meth:`DataFrame.to_sql` when reading DataFrames with ``-np.inf`` entries with MySQL now has a more explicit ``ValueError`` (:issue:`34431`)
-- Bug in :meth:`io.common.infer_compression` where capitalised files extensions were not decompressed by read_* functions.
+- Bug where capitalised files extensions were not decompressed by read_* functions (:issue:`35164`)
 
 Plotting
 ^^^^^^^^