From 5a4b50b3772cb3db48a0c603cef5a39ff96f442c Mon Sep 17 00:00:00 2001
From: Quang Nguyen <chox.negi@gmail.com>
Date: Sun, 17 Mar 2024 20:52:49 +0700
Subject: [PATCH 1/3] add warning

---
 pandas/io/common.py | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index 35c3a24d8e8f6..abb26b0ffefaa 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -361,6 +361,19 @@ def _get_filepath_or_buffer(
             stacklevel=find_stack_level(),
         )
 
+    if (
+        "a" in mode
+        and compression_method in ["zip", "tar"]
+    ):
+        # GH56778
+        warnings.warn(
+            "zip and tar do not support mode 'a' properly. "
+            "This combination will result in multiple files with same name "
+            "being added to the archive.",
+            RuntimeWarning,
+            stacklevel=find_stack_level(),
+        )
+
     # Use binary mode when converting path-like objects to file-like objects (fsspec)
     # except when text mode is explicitly requested. The original mode is returned if
     # fsspec is not used.

From 091a513bf7d9e3dd57e42815e327d7e131adf7e3 Mon Sep 17 00:00:00 2001
From: Quang Nguyen <chox.negi@gmail.com>
Date: Wed, 20 Mar 2024 10:14:03 +0700
Subject: [PATCH 2/3] add test

---
 pandas/tests/frame/methods/test_to_csv.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/pandas/tests/frame/methods/test_to_csv.py b/pandas/tests/frame/methods/test_to_csv.py
index 5b9ced8d47ed7..f87fa4137d62d 100644
--- a/pandas/tests/frame/methods/test_to_csv.py
+++ b/pandas/tests/frame/methods/test_to_csv.py
@@ -1405,3 +1405,20 @@ def test_to_csv_categorical_and_interval(self):
         expected_rows = [",a", '0,"[2020-01-01 00:00:00, 2020-01-02 00:00:00]"']
         expected = tm.convert_rows_list_to_csv_str(expected_rows)
         assert result == expected
+
+    def test_to_csv_warn_when_zip_tar_and_append_mode(self):
+        # GH57875
+        df = DataFrame({"a": [1, 2, 3]})
+        msg = (
+            "zip and tar do not support mode 'a' properly. This combination will "
+            "result in multiple files with same name being added to the archive"
+        )
+        with tm.assert_produces_warning(
+            RuntimeWarning, match=msg, raise_on_extra_warnings=False
+        ):
+            df.to_csv("test.zip", mode="a")
+
+        with tm.assert_produces_warning(
+            RuntimeWarning, match=msg, raise_on_extra_warnings=False
+        ):
+            df.to_csv("test.tar", mode="a")

From b6920aabee7dc3ace30eb599eed40f3722318df6 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Wed, 20 Mar 2024 03:35:59 +0000
Subject: [PATCH 3/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 pandas/io/common.py | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/pandas/io/common.py b/pandas/io/common.py
index abb26b0ffefaa..4507a7d08c8ba 100644
--- a/pandas/io/common.py
+++ b/pandas/io/common.py
@@ -361,10 +361,7 @@ def _get_filepath_or_buffer(
             stacklevel=find_stack_level(),
         )
 
-    if (
-        "a" in mode
-        and compression_method in ["zip", "tar"]
-    ):
+    if "a" in mode and compression_method in ["zip", "tar"]:
         # GH56778
         warnings.warn(
             "zip and tar do not support mode 'a' properly. "