add tests

Author: aram-cedarwood

pandas/core/computation/parsing.py

@@ -216,13 +216,13 @@ def _split_by_backtick(s: str) -> list[tuple[bool, str]]:
         if (quote_index == -1) or (backtick_index < quote_index):
             next_backtick_index = s.find("`", backtick_index + 1)
 
-            # Backtick is unmatched (Possibly a mistake)
+            # Backtick is unmatched (Bad syntax)
             if next_backtick_index == -1:
                 substrings.append((False, substring + s[i:]))
                 break
             # Backtick is matched
             else:
-                if i != backtick_index:
+                if substring or (i != backtick_index):
                     substrings.append((False, substring + s[i:backtick_index]))
                 substrings.append((True, s[backtick_index : next_backtick_index + 1]))
                 substring = ""
@@ -238,19 +238,15 @@ def _split_by_backtick(s: str) -> list[tuple[bool, str]]:
                     next_quote_index = i + end - 1
                     break
 
-            # Quote is unmatched (Possibly a mistake)
-            if next_quote_index == -1:
-                substrings.append((False, substring + s[i:]))
-                break
+            # Quote is unmatched (Bad syntax), or
             # Quote is matched, and the next quote is at the end of the string
-            elif next_quote_index + 1 == len(s):
+            if (next_quote_index == -1) or (next_quote_index + 1 == len(s)):
                 substrings.append((False, substring + s[i:]))
                 break
             # Quote is matched, and the next quote is in the middle of the string
             else:
                 substring += s[i : next_quote_index + 1]
                 i = next_quote_index + 1
-                continue
 
     return substrings
 

pandas/tests/computation/test_eval.py

@@ -2034,6 +2034,67 @@ def test_query_on_column_names_with_special_characters(col1, col2, expr):
     tm.assert_frame_equal(result, expected)
 
 
+def test_query_on_expr_with_no_backticks():
+    # GH 59285
+    df = DataFrame(("aaa", "vvv", "zzz"), columns=["column_name"])
+    result = df.query("'value' < column_name")
+    expected = df["value" < df["column_name"]]
+    tm.assert_frame_equal(result, expected)
+
+
+def test_query_on_expr_with_no_quotes_and_backtick_is_unmatched():
+    # GH 59285
+    df = DataFrame((1, 5, 10), columns=["column-name"])
+    with pytest.raises(SyntaxError, match="invalid syntax"):
+        df.query("5 < `column-name")
+
+
+def test_query_on_expr_with_no_quotes_and_backtick_is_matched():
+    # GH 59285
+    df = DataFrame((1, 5, 10), columns=["column-name"])
+    result = df.query("5 < `column-name`")
+    expected = df[5 < df["column-name"]]
+    tm.assert_frame_equal(result, expected)
+
+
+def test_query_on_expr_with_backtick_opened_before_quote_and_backtick_is_unmatched():
+    # GH 59285
+    df = DataFrame((1, 5, 10), columns=["It's"])
+    with pytest.raises(SyntaxError, match="unterminated string literal"):
+        df.query("5 < `It's")
+
+
+def test_query_on_expr_with_backtick_opened_before_quote_and_backtick_is_matched():
+    # GH 59285
+    df = DataFrame((1, 5, 10), columns=["It's"])
+    result = df.query("5 < `It's`")
+    expected = df[5 < df["It's"]]
+    tm.assert_frame_equal(result, expected)
+
+
+def test_query_on_expr_with_quote_opened_before_backtick_and_quote_is_unmatched():
+    # GH 59285
+    df = DataFrame(("aaa", "vvv", "zzz"), columns=['It`s that\\\'s "quote" #hash'])
+    with pytest.raises(SyntaxError, match="unterminated string literal"):
+        df.query("`column-name` < 'It`s that\\'s \"quote\" #hash")
+
+
+def test_query_on_expr_with_quote_opened_before_backtick_and_quote_is_matched_at_end():
+    # GH 59285
+    df = DataFrame(("aaa", "vvv", "zzz"), columns=["column-name"])
+    result = df.query("`column-name` < 'It`s that\\'s \"quote\" #hash'")
+    expected = df[df["column-name"] < 'It`s that\'s "quote" #hash']
+    tm.assert_frame_equal(result, expected)
+
+
+def test_query_on_expr_with_quote_opened_before_backtick_and_quote_is_matched_in_mid():
+    # GH 59285
+    df = DataFrame(("aaa", "vvv", "zzz"), columns=["column-name"])
+    result = df.query("'It`s that\\'s \"quote\" #hash' < `column-name`")
+    expected = df['It`s that\'s "quote" #hash' < df["column-name"]]
+    tm.assert_frame_equal(result, expected)
+
+
 def test_set_inplace():
     # https://github.com/pandas-dev/pandas/issues/47449
     # Ensure we don't only update the DataFrame inplace, but also the actual