97 lines
3.2 KiB
Python
97 lines
3.2 KiB
Python
import argparse
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from pathlib import Path
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import httpx
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import polars as pl
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# UK Parliament publishes candidate-level results for the 2024 General Election.
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# One row per candidate per constituency — we aggregate to per-constituency stats.
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URL = "https://electionresults.parliament.uk/general-elections/6/candidacies.csv"
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# Map party names to a smaller set for vote share columns.
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# Only parties that won seats in England are kept; the rest become "Other parties".
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PARTY_MAP = {
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"Labour": "Labour",
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"Conservative": "Conservative",
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"Liberal Democrat": "Liberal Democrat",
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"Reform UK": "Reform UK",
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"Green Party": "Green",
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}
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def download_and_convert(output_path: Path) -> None:
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print("Downloading 2024 General Election results...")
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response = httpx.get(URL, follow_redirects=True, timeout=60)
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response.raise_for_status()
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df = pl.read_csv(response.content)
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print(f"Raw shape: {df.shape}")
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# Filter to England only (constituency codes starting with E14)
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df = df.filter(pl.col("Constituency geographic code").str.starts_with("E14"))
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# Map party names to our output groups
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df = df.with_columns(
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pl.col("Main party name")
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.replace_strict(PARTY_MAP, default="Other parties")
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.alias("party_group"),
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)
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# ── Per-constituency turnout ──
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turnout = df.filter(pl.col("Candidate result position") == 1).select(
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pl.col("Constituency geographic code").alias("pcon"),
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(pl.col("Election valid vote count") / pl.col("Electorate") * 100)
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.round(1)
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.alias("turnout_pct"),
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)
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# ── Per-party vote share percentages ──
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# Sum votes per party group per constituency, then pivot to wide format
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party_votes = (
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df.group_by("Constituency geographic code", "party_group")
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.agg(pl.col("Candidate vote count").sum())
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.rename({"Constituency geographic code": "pcon"})
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)
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total_votes = (
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df.group_by("Constituency geographic code")
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.agg(pl.col("Candidate vote count").sum().alias("total_votes"))
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.rename({"Constituency geographic code": "pcon"})
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)
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party_pct = (
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party_votes.join(total_votes, on="pcon")
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.with_columns(
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(pl.col("Candidate vote count") / pl.col("total_votes") * 100)
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.round(1)
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.alias("vote_pct"),
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)
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.pivot(on="party_group", index="pcon", values="vote_pct")
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)
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# Rename columns to "% Party" format
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rename_map = {col: f"% {col}" for col in party_pct.columns if col != "pcon"}
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party_pct = party_pct.rename(rename_map)
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# Join turnout with party vote shares
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result = turnout.join(party_pct, on="pcon", how="left")
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print(f"Constituencies: {result.height}")
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print(f"Columns: {result.columns}")
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output_path.parent.mkdir(parents=True, exist_ok=True)
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result.write_parquet(output_path, compression="zstd")
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print(f"Saved to {output_path}")
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def main() -> None:
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parser = argparse.ArgumentParser(
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description="Download 2024 General Election results by constituency"
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)
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parser.add_argument(
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"--output", type=Path, required=True, help="Output parquet file path"
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)
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args = parser.parse_args()
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download_and_convert(args.output)
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if __name__ == "__main__":
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main()
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