add test

narwhals/utils.py

@@ -964,7 +964,10 @@ def _validate_rolling_arguments(
 
 
 def generate_repr(header: str, native_repr: str) -> str:
-    terminal_width = os.get_terminal_size().columns
+    try:
+        terminal_width = os.get_terminal_size().columns
+    except OSError:
+        terminal_width = 80
     native_lines = native_repr.splitlines()
     max_native_width = max(len(line) for line in native_lines)
 
@@ -976,8 +979,8 @@ def generate_repr(header: str, native_repr: str) -> str:
             f"|{' '*(header_extra//2)}{header}{' '*(header_extra//2 + header_extra%2)}|\n"
         )
         output += f"|{'-'*(length)}|\n"
-        start_extra = (max_native_width - length) // 2
-        end_extra = (max_native_width - length) // 2 + (max_native_width - length) % 2
+        start_extra = (length - max_native_width) // 2
+        end_extra = (length - max_native_width) // 2 + (length - max_native_width) % 2
         for line in native_lines:
             output += f"|{' '*(start_extra)}{line}{' '*(end_extra + max_native_width - len(line))}|\n"
         output += f"└{'─' * length}┘"
@@ -987,5 +990,6 @@ def generate_repr(header: str, native_repr: str) -> str:
     return (
         f"┌{'─' * (39)}┐\n"
         f"|{' '*(diff//2)}{header}{' '*(diff//2+diff%2)}|\n"
-        "| Use `.to_native` to see native output |\n" + "└" + "─" * 39 + "┘"
+        "| Use `.to_native` to see native output |\n└"
+        f"{'─' * 39}┘"
     )

tests/repr_test.py

@@ -0,0 +1,73 @@
+from __future__ import annotations
+
+import pandas as pd
+import pytest
+
+import narwhals.stable.v1 as nw
+
+
+def test_repr() -> None:
+    duckdb = pytest.importorskip("duckdb")
+    df = pd.DataFrame({"a": [1, 2, 3], "b": ["fdaf", "fda", "cf"]})
+    result = nw.from_native(df).__repr__()
+    expected = (
+        "┌──────────────────┐\n"
+        "|Narwhals DataFrame|\n"
+        "|------------------|\n"
+        "|       a     b    |\n"
+        "|    0  1  fdaf    |\n"
+        "|    1  2   fda    |\n"
+        "|    2  3    cf    |\n"
+        "└──────────────────┘"
+    )
+    assert result == expected
+    result = nw.from_native(df).lazy().__repr__()
+    expected = (
+        "┌──────────────────┐\n"
+        "|Narwhals LazyFrame|\n"
+        "|------------------|\n"
+        "|       a     b    |\n"
+        "|    0  1  fdaf    |\n"
+        "|    1  2   fda    |\n"
+        "|    2  3    cf    |\n"
+        "└──────────────────┘"
+    )
+    assert result == expected
+    result = nw.from_native(df)["a"].__repr__()
+    expected = (
+        "┌─────────────────────┐\n"
+        "|   Narwhals Series   |\n"
+        "|---------------------|\n"
+        "|0    1               |\n"
+        "|1    2               |\n"
+        "|2    3               |\n"
+        "|Name: a, dtype: int64|\n"
+        "└─────────────────────┘"
+    )
+    assert result == expected
+    result = nw.from_native(duckdb.table("df")).__repr__()
+    expected = (
+        "┌───────────────────┐\n"
+        "|Narwhals DataFrame |\n"
+        "|-------------------|\n"
+        "|┌───────┬─────────┐|\n"
+        "|│   a   │    b    │|\n"
+        "|│ int64 │ varchar │|\n"
+        "|├───────┼─────────┤|\n"
+        "|│     1 │ fdaf    │|\n"
+        "|│     2 │ fda     │|\n"
+        "|│     3 │ cf      │|\n"
+        "|└───────┴─────────┘|\n"
+        "└───────────────────┘"
+    )
+    assert result == expected
+    # Make something wider than the terminal size
+    df = pd.DataFrame({"a": [1, 2, 3], "b": ["fdaf" * 100, "fda", "cf"]})
+    result = nw.from_native(duckdb.table("df")).__repr__()
+    expected = (
+        "┌───────────────────────────────────────┐\n"
+        "|          Narwhals DataFrame           |\n"
+        "| Use `.to_native` to see native output |\n"
+        "└───────────────────────────────────────┘"
+    )
+    assert result == expected