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fix: Method str.zfill was inconsistent with Python and pandas when string contained leading '+' #22985

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Merged
merged 3 commits into from
May 28, 2025
Merged

fix: Method str.zfill was inconsistent with Python and pandas when string contained leading '+' #22985

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168d410
fix: Method was inconsistent with Python and pandas when string cont…
MarcoGorelli May 28, 2025
361d00c
avoid unstable if let
MarcoGorelli May 28, 2025
7636953
just keep it simple
MarcoGorelli May 28, 2025
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21 changes: 5 additions & 16 deletions crates/polars-ops/src/chunked_array/strings/pad.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -59,24 +59,13 @@ fn zfill_fn<'a>(s: Option<&'a str>, len: Option<u64>, buf: &mut String) -> Optio
return Some(s);
}
buf.clear();
let length = length as usize;
if let Some(stripped) = s.strip_prefix('-') {
write!(
buf,
"-{:0length$}{value}",
0,
length = length as usize,
value = stripped
)
.unwrap();
write!(buf, "-{:0length$}{stripped}", 0,).unwrap();
} else if let Some(stripped) = s.strip_prefix('+') {
write!(buf, "+{:0length$}{stripped}", 0,).unwrap();
} else {
write!(
buf,
"{:0length$}{value}",
0,
length = length as usize,
value = s
)
.unwrap();
write!(buf, "{:0length$}{s}", 0,).unwrap();
};
// extend lifetime
// lifetime is bound to 'a
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19 changes: 14 additions & 5 deletions py-polars/tests/unit/operations/namespaces/string/test_pad.py
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Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,8 @@ def test_str_zfill() -> None:
def test_str_zfill_expr() -> None:
df = pl.DataFrame(
{
"num": ["-10", "-1", "0", "1", "10", None, "1"],
"len": [3, 4, 3, 2, 5, 3, None],
"num": ["-10", "-1", "0", "1", "10", None, "1", "+1"],
"len": [3, 4, 3, 2, 5, 3, None, 3],
}
)
out = df.select(
Expand All @@ -83,9 +83,18 @@ def test_str_zfill_expr() -> None:
)
expected = pl.DataFrame(
{
"all_expr": ["-10", "-001", "000", "01", "00010", None, None],
"str_lit": ["010", "0010", "010", "10", "00010", "010", None],
"len_lit": ["-0010", "-0001", "00000", "00001", "00010", None, "00001"],
"all_expr": ["-10", "-001", "000", "01", "00010", None, None, "+01"],
"str_lit": ["010", "0010", "010", "10", "00010", "010", None, "010"],
"len_lit": [
"-0010",
"-0001",
"00000",
"00001",
"00010",
None,
"00001",
"+0001",
],
}
)
assert_frame_equal(out, expected)
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