commit 2134b14ef63171359793bbd59a696f02988ee425
Author: David Rice <david.rice@arrive.com>
Date:   Wed Apr 29 19:55:19 2026 +0100

    first commit

diff --git a/.env.example b/.env.example
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+# ── DigiKey ────────────────────────────────────────────────────────────────────
+# Register at https://developer.digikey.com/ → Create an organisation → Add a
+# production app → copy the Client ID and Client Secret below.
+DIGIKEY_CLIENT_ID=
+DIGIKEY_CLIENT_SECRET=
+
+# ── Mouser ─────────────────────────────────────────────────────────────────────
+# Register at https://www.mouser.com/api-hub/ → Apply for a Search API key.
+MOUSER_API_KEY=
+
+# ── Farnell / Element14 ────────────────────────────────────────────────────────
+# Register at https://partner.element14.com/ → My Account → Manage API Keys.
+# FARNELL_STORE controls which regional store is queried for pricing.
+# Examples: fr.farnell.com  de.farnell.com  uk.farnell.com  ie.farnell.com
+FARNELL_API_KEY=
+FARNELL_STORE=fr.farnell.com
+
+# ── RS Components ──────────────────────────────────────────────────────────────
+# Register at https://developers.rs-online.com/ → Create an application.
+RS_API_KEY=
diff --git a/BoM/Axio4_Nexio_Conduent Subsystem Cost Analysis.xlsx b/BoM/Axio4_Nexio_Conduent Subsystem Cost Analysis.xlsx
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index 0000000..28a9d19
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diff --git a/README.md b/README.md
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+++ b/README.md
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+# Introduction 
+BoM to Supplier Costing - Python
diff --git a/bom_price_checker.py b/bom_price_checker.py
new file mode 100644
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--- /dev/null
+++ b/bom_price_checker.py
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+#!/usr/bin/env python3
+"""
+BoM Price Checker
+=================
+Reads every .xlsx / .xlsm file from the BoM/ folder.
+Each file may have many sheets, and each sheet may have many tables.
+A "table" is any block of rows that begins with a header row containing
+both a 'Manufacturer' column and an 'MPN' column.
+
+For every unique (Manufacturer, MPN) pair found, the script queries:
+  - DigiKey  (v4 API  – developer.digikey.com)
+  - Mouser   (v1 API  – mouser.com/api-hub)
+  - Farnell  (Element14 API – partner.element14.com)
+  - RS Components (v2 API – developers.rs-online.com)
+
+All prices are converted to EUR at quantity 1000 using live FX rates
+from Frankfurter (api.frankfurter.app – free, no key required).
+
+Results are written back into the original BoM files as a new column
+"Unit Cost 1000x Data" placed at the end of each component table.
+Cells that already contain a value are left untouched.
+
+Cached results are stored in price_cache.json and reused for 7 days.
+
+Quick start
+-----------
+  pip install -r requirements.txt
+  cp .env.example .env        # then add your API keys
+  python bom_price_checker.py
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+import json
+import time
+import logging
+from dataclasses import dataclass, field
+from datetime import datetime, timedelta
+from pathlib import Path
+from typing import Optional
+
+import requests
+import openpyxl
+import pandas as pd
+from dotenv import load_dotenv
+
+load_dotenv()
+
+# ── Configuration ──────────────────────────────────────────────────────────────
+
+BOM_DIR        = Path("BoM")
+CACHE_FILE     = Path("price_cache.json")
+QUANTITY       = 1000
+CACHE_TTL_DAYS = 7
+REQUEST_DELAY  = 0.35   # seconds between successive API calls
+COST_HEADER    = "Unit Cost 1000x Data"
+
+# MPN cell values that mean "no part fitted / TBD" – skip these
+SKIP_MPNS = {
+    "", "tbd", "n/a", "na", "-", "--", "---", "?", "none",
+    "null", "nan", "xxx", "x", "dnf", "dnp", "do not fit",
+    "do not populate",
+}
+
+# ── Logging ────────────────────────────────────────────────────────────────────
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s  %(levelname)-8s  %(message)s",
+    datefmt="%H:%M:%S",
+)
+log = logging.getLogger(__name__)
+
+# ── Currency conversion ────────────────────────────────────────────────────────
+
+_fx_cache: dict[str, float] = {}
+
+
+def eur_rate(currency: str) -> float:
+    """Return how many EUR equal 1 unit of *currency* (Frankfurter API, no key needed)."""
+    currency = currency.upper().strip()
+    if currency == "EUR":
+        return 1.0
+    if currency in _fx_cache:
+        return _fx_cache[currency]
+    try:
+        r = requests.get(
+            "https://api.frankfurter.app/latest",
+            params={"from": currency, "to": "EUR"},
+            timeout=10,
+        )
+        r.raise_for_status()
+        rate: float = r.json()["rates"]["EUR"]
+        _fx_cache[currency] = rate
+        log.debug(f"FX  1 {currency} = {rate:.5f} EUR")
+        return rate
+    except Exception as exc:
+        log.warning(f"FX lookup failed ({currency}→EUR): {exc} – defaulting to 1.0")
+        return 1.0
+
+
+def to_eur(amount: float, currency: str) -> float:
+    return round(amount * eur_rate(currency), 5)
+
+
+# ── Price cache ────────────────────────────────────────────────────────────────
+
+class PriceCache:
+    def __init__(self, path: Path) -> None:
+        self.path = path
+        self._data: dict[str, dict] = {}
+        self._load()
+
+    def _load(self) -> None:
+        if self.path.exists():
+            try:
+                self._data = json.loads(self.path.read_text(encoding="utf-8"))
+            except (json.JSONDecodeError, OSError):
+                self._data = {}
+
+    def save(self) -> None:
+        self.path.write_text(json.dumps(self._data, indent=2), encoding="utf-8")
+
+    @staticmethod
+    def _key(manufacturer: str, mpn: str) -> str:
+        return f"{manufacturer.strip().lower()}||{mpn.strip().lower()}"
+
+    def get(self, manufacturer: str, mpn: str) -> Optional[dict]:
+        entry = self._data.get(self._key(manufacturer, mpn))
+        if not entry:
+            return None
+        try:
+            age = datetime.now() - datetime.fromisoformat(entry["cached_at"])
+        except (KeyError, ValueError):
+            return None
+        return entry if age <= timedelta(days=CACHE_TTL_DAYS) else None
+
+    def put(self, manufacturer: str, mpn: str, prices: dict) -> None:
+        prices["cached_at"] = datetime.now().isoformat()
+        self._data[self._key(manufacturer, mpn)] = prices
+        self.save()
+
+
+# ── BoM parsing ────────────────────────────────────────────────────────────────
+
+def _cell(value) -> str:
+    return str(value).strip() if value is not None else ""
+
+
+def _skip(mpn: str) -> bool:
+    return mpn.lower() in SKIP_MPNS
+
+
+@dataclass
+class TableLocation:
+    """Records exactly where a component table lives inside a worksheet."""
+    sheet_name: str
+    header_row: int                          # 1-based openpyxl row
+    mfr_col:    int                          # 1-based openpyxl column
+    mpn_col:    int                          # 1-based openpyxl column
+    data:       list[tuple[int, str, str]] = field(default_factory=list)
+    # data entries: (1-based row number, manufacturer string, mpn string)
+
+
+def _find_tables(indexed_rows: list[tuple[int, tuple]]) -> list[TableLocation]:
+    """
+    Scan a list of (1-based-row-num, row-values-tuple) pairs for sub-tables
+    that have both a 'Manufacturer' and 'MPN' header column.
+    """
+    tables: list[TableLocation] = []
+    i = 0
+    while i < len(indexed_rows):
+        row_num, row = indexed_rows[i]
+        row_str = [_cell(v) for v in row]
+
+        mfr_col_0 = next((c for c, v in enumerate(row_str) if v.lower() == "manufacturer"), None)
+        mpn_col_0 = next((c for c, v in enumerate(row_str) if v.lower() == "mpn"), None)
+
+        if mfr_col_0 is None or mpn_col_0 is None:
+            i += 1
+            continue
+
+        # Found a header row – consume data rows below it
+        data: list[tuple[int, str, str]] = []
+        j = i + 1
+        empty_streak = 0
+        while j < len(indexed_rows):
+            dr_num, dr = indexed_rows[j]
+            mfr = _cell(dr[mfr_col_0] if mfr_col_0 < len(dr) else None)
+            mpn = _cell(dr[mpn_col_0] if mpn_col_0 < len(dr) else None)
+
+            if not mfr and not mpn:
+                empty_streak += 1
+                if empty_streak >= 3:
+                    break
+                j += 1
+                continue
+            empty_streak = 0
+
+            # Another header row signals the end of this table
+            if mfr.lower() == "manufacturer" and mpn.lower() == "mpn":
+                break
+
+            if mpn and not _skip(mpn):
+                data.append((dr_num, mfr, mpn))
+            j += 1
+
+        tables.append(TableLocation(
+            sheet_name="",          # filled by caller
+            header_row=row_num,
+            mfr_col=mfr_col_0 + 1,  # convert to 1-based
+            mpn_col=mpn_col_0 + 1,
+            data=data,
+        ))
+        i = j  # jump past the table we just consumed
+    return tables
+
+
+def extract_parts(
+    bom_dir: Path,
+) -> tuple[dict[Path, list[TableLocation]], set[tuple[str, str]]]:
+    """
+    Returns:
+      file_map  – {file_path: [TableLocation, ...]} for write-back
+      parts     – set of unique (manufacturer, mpn) pairs for API lookup
+    """
+    file_map: dict[Path, list[TableLocation]] = {}
+    parts: set[tuple[str, str]] = set()
+
+    all_files = sorted(bom_dir.iterdir())
+    xlsx_files = [f for f in all_files if f.suffix.lower() in {".xlsx", ".xlsm"}]
+    other_files = [f for f in all_files if f.suffix.lower() in {".xls", ".csv"}]
+
+    for f in other_files:
+        log.warning(
+            f"Skipping {f.name}  "
+            f"({'read-only; price write-back requires .xlsx' if f.suffix.lower() == '.xls' else 'CSV – convert to .xlsx for write-back'})"
+        )
+
+    if not xlsx_files:
+        log.warning(f"No .xlsx/.xlsm files found in {bom_dir}/")
+        return file_map, parts
+
+    for f in xlsx_files:
+        log.info(f"Reading  {f.name}")
+        tables_in_file: list[TableLocation] = []
+        try:
+            wb = openpyxl.load_workbook(f, data_only=True, read_only=True)
+            for sheet_name in wb.sheetnames:
+                ws = wb[sheet_name]
+                indexed = [
+                    (row_num, tuple(row))
+                    for row_num, row in enumerate(ws.iter_rows(values_only=True), start=1)
+                ]
+                tables = _find_tables(indexed)
+                for t in tables:
+                    t.sheet_name = sheet_name
+                if tables:
+                    total_parts = sum(len(t.data) for t in tables)
+                    log.info(f"  Sheet '{sheet_name}': {len(tables)} table(s), {total_parts} part rows")
+                    for t in tables:
+                        for _, mfr, mpn in t.data:
+                            parts.add((mfr, mpn))
+                tables_in_file.extend(tables)
+            wb.close()
+        except Exception as exc:
+            log.error(f"  Failed to read {f.name}: {exc}")
+            continue
+
+        if tables_in_file:
+            file_map[f] = tables_in_file
+
+    log.info(f"Unique (Manufacturer, MPN) pairs: {len(parts)}")
+    return file_map, parts
+
+
+# ── Distributor API clients ────────────────────────────────────────────────────
+
+class DigiKeyClient:
+    """DigiKey API v4.  Register at developer.digikey.com for a Client ID + Secret."""
+
+    _TOKEN_URL  = "https://api.digikey.com/v1/oauth2/token"
+    _SEARCH_URL = "https://api.digikey.com/products/v4/search/keyword"
+
+    def __init__(self) -> None:
+        self.client_id     = os.getenv("DIGIKEY_CLIENT_ID", "")
+        self.client_secret = os.getenv("DIGIKEY_CLIENT_SECRET", "")
+        self._access_token: Optional[str] = None
+        self._token_expiry = datetime.min
+
+    @property
+    def configured(self) -> bool:
+        return bool(self.client_id and self.client_secret)
+
+    def _get_token(self) -> Optional[str]:
+        if not self.configured:
+            return None
+        if self._access_token and datetime.now() < self._token_expiry:
+            return self._access_token
+        try:
+            r = requests.post(
+                self._TOKEN_URL,
+                data={
+                    "client_id":     self.client_id,
+                    "client_secret": self.client_secret,
+                    "grant_type":    "client_credentials",
+                },
+                timeout=15,
+            )
+            r.raise_for_status()
+            data = r.json()
+            self._access_token = data["access_token"]
+            self._token_expiry = datetime.now() + timedelta(
+                seconds=data.get("expires_in", 1800) - 60
+            )
+            return self._access_token
+        except Exception as exc:
+            log.debug(f"DigiKey token error: {exc}")
+            return None
+
+    def get_price_eur(self, manufacturer: str, mpn: str) -> Optional[float]:
+        token = self._get_token()
+        if not token:
+            return None
+        try:
+            r = requests.post(
+                self._SEARCH_URL,
+                headers={
+                    "X-DIGIKEY-Client-Id":      self.client_id,
+                    "Authorization":             f"Bearer {token}",
+                    "X-DIGIKEY-Locale-Site":     "FR",
+                    "X-DIGIKEY-Locale-Language": "fr",
+                    "X-DIGIKEY-Locale-Currency": "EUR",
+                    "Content-Type":              "application/json",
+                },
+                json={"keywords": mpn, "limit": 10, "offset": 0},
+                timeout=15,
+            )
+            r.raise_for_status()
+            data = r.json()
+
+            candidates = (
+                data.get("exactManufacturerProducts")
+                or data.get("exactManufacturerProductCount", [])
+                or []
+            )
+            if not candidates:
+                candidates = data.get("products", [])
+
+            for product in candidates:
+                if product.get("manufacturerProductNumber", "").lower() == mpn.lower():
+                    p = self._price_at_qty(product)
+                    if p is not None:
+                        return p
+            if candidates:
+                return self._price_at_qty(candidates[0])
+        except Exception as exc:
+            log.debug(f"DigiKey error [{mpn}]: {exc}")
+        return None
+
+    @staticmethod
+    def _price_at_qty(product: dict) -> Optional[float]:
+        breaks = product.get("standardPricing") or product.get("priceBreaks") or []
+        best: Optional[float] = None
+        for pb in breaks:
+            try:
+                qty   = int(pb.get("breakQuantity") or pb.get("quantity") or 0)
+                price = float(pb.get("unitPrice") or pb.get("price") or 0)
+                if qty <= QUANTITY and price > 0:
+                    best = price  # already EUR via locale header
+            except (ValueError, TypeError):
+                continue
+        return best
+
+
+class MouserClient:
+    """Mouser Electronics API v1.  Register at mouser.com/api-hub."""
+
+    _URL = "https://api.mouser.com/api/v1/search/partnumber"
+
+    def __init__(self) -> None:
+        self.api_key = os.getenv("MOUSER_API_KEY", "")
+
+    @property
+    def configured(self) -> bool:
+        return bool(self.api_key)
+
+    def get_price_eur(self, manufacturer: str, mpn: str) -> Optional[float]:
+        if not self.configured:
+            return None
+        try:
+            r = requests.post(
+                f"{self._URL}?apiKey={self.api_key}&currency=EUR",
+                json={"SearchByPartRequest": {"mouserPartNumber": mpn, "partSearchOptions": ""}},
+                timeout=15,
+            )
+            r.raise_for_status()
+            part_list = r.json().get("SearchResults", {}).get("Parts", [])
+
+            for part in part_list:
+                if part.get("ManufacturerPartNumber", "").lower() == mpn.lower():
+                    p = self._price_at_qty(part)
+                    if p is not None:
+                        return p
+            if part_list:
+                return self._price_at_qty(part_list[0])
+        except Exception as exc:
+            log.debug(f"Mouser error [{mpn}]: {exc}")
+        return None
+
+    @staticmethod
+    def _price_at_qty(part: dict) -> Optional[float]:
+        currency = part.get("PricingCurrencyCode", "EUR")
+        best: Optional[float] = None
+        for pb in part.get("PriceBreaks", []):
+            try:
+                qty = int(pb.get("Quantity", 0))
+                raw = str(pb.get("Price", "")).strip()
+                for sym in ("€", "$", "£", "¥", ","):
+                    raw = raw.replace(sym, "")
+                price = float(raw)
+                if qty <= QUANTITY and price > 0:
+                    best = to_eur(price, currency)
+            except (ValueError, TypeError):
+                continue
+        return best
+
+
+class FarnellClient:
+    """Farnell / Element14 API.  Register at partner.element14.com."""
+
+    _URL = "https://api.element14.com/catalog/products"
+
+    def __init__(self) -> None:
+        self.api_key = os.getenv("FARNELL_API_KEY", "")
+        # Change to e.g. "de.farnell.com" for German pricing
+        self.store   = os.getenv("FARNELL_STORE", "fr.farnell.com")
+
+    @property
+    def configured(self) -> bool:
+        return bool(self.api_key)
+
+    def get_price_eur(self, manufacturer: str, mpn: str) -> Optional[float]:
+        if not self.configured:
+            return None
+        try:
+            r = requests.get(
+                self._URL,
+                params={
+                    "term":                             f"mfrPartNum:{mpn}",
+                    "storeInfo.id":                     self.store,
+                    "resultsSettings.offset":           0,
+                    "resultsSettings.numberOfResults":  5,
+                    "resultsSettings.responseGroup":    "prices",
+                    "callInfo.omitXmlSchema":           "false",
+                    "callInfo.responseDataFormat":      "json",
+                    "callInfo.apiKey":                  self.api_key,
+                },
+                timeout=15,
+            )
+            r.raise_for_status()
+            products = r.json().get("keywordSearchReturn", {}).get("products", [])
+
+            for product in products:
+                pn = product.get("translatedManufacturerPartNumber") or product.get("id", "")
+                if str(pn).lower() == mpn.lower():
+                    p = self._price_at_qty(product)
+                    if p is not None:
+                        return p
+            if products:
+                return self._price_at_qty(products[0])
+        except Exception as exc:
+            log.debug(f"Farnell error [{mpn}]: {exc}")
+        return None
+
+    @staticmethod
+    def _price_at_qty(product: dict) -> Optional[float]:
+        currency = product.get("currency", "EUR")
+        best: Optional[float] = None
+        for pb in product.get("prices", []):
+            try:
+                qty   = int(pb.get("from", 0))
+                price = float(pb.get("cost", 0))
+                if qty <= QUANTITY and price > 0:
+                    best = to_eur(price, currency)
+            except (ValueError, TypeError):
+                continue
+        return best
+
+
+class RSClient:
+    """RS Components API v2.  Register at developers.rs-online.com."""
+
+    _URL = "https://api.rs-online.com/searchProducts/v2/search"
+
+    def __init__(self) -> None:
+        self.api_key = os.getenv("RS_API_KEY", "")
+
+    @property
+    def configured(self) -> bool:
+        return bool(self.api_key)
+
+    def get_price_eur(self, manufacturer: str, mpn: str) -> Optional[float]:
+        if not self.configured:
+            return None
+        try:
+            r = requests.get(
+                self._URL,
+                params={
+                    "term":   mpn,
+                    "fields": "prices,partNumber,manufacturer,manufacturerPartNumber",
+                    "size":   5,
+                },
+                headers={"apiKey": self.api_key},
+                timeout=15,
+            )
+            r.raise_for_status()
+            products = r.json().get("products", [])
+
+            for product in products:
+                pn = product.get("manufacturerPartNumber", "")
+                if str(pn).lower() == mpn.lower():
+                    p = self._price_at_qty(product)
+                    if p is not None:
+                        return p
+            if products:
+                return self._price_at_qty(products[0])
+        except Exception as exc:
+            log.debug(f"RS error [{mpn}]: {exc}")
+        return None
+
+    @staticmethod
+    def _price_at_qty(product: dict) -> Optional[float]:
+        currency = product.get("priceCurrency", "EUR")
+        best: Optional[float] = None
+        for pb in product.get("prices", []):
+            try:
+                qty   = int(pb.get("from") or pb.get("quantity") or 0)
+                price = float(pb.get("price") or pb.get("unitPrice") or 0)
+                if qty <= QUANTITY and price > 0:
+                    best = to_eur(price, currency)
+            except (ValueError, TypeError):
+                continue
+        return best
+
+
+# ── Result dataclass ───────────────────────────────────────────────────────────
+
+@dataclass
+class PartResult:
+    manufacturer: str
+    mpn: str
+    digikey_eur: Optional[float] = None
+    mouser_eur:  Optional[float] = None
+    farnell_eur: Optional[float] = None
+    rs_eur:      Optional[float] = None
+
+    @property
+    def average_eur(self) -> Optional[float]:
+        vals = [v for v in (self.digikey_eur, self.mouser_eur, self.farnell_eur, self.rs_eur)
+                if v is not None]
+        return round(sum(vals) / len(vals), 5) if vals else None
+
+    def sources_found(self) -> int:
+        return sum(v is not None for v in
+                   (self.digikey_eur, self.mouser_eur, self.farnell_eur, self.rs_eur))
+
+
+# ── API lookup with caching ────────────────────────────────────────────────────
+
+def lookup(
+    manufacturer: str,
+    mpn: str,
+    cache: PriceCache,
+    dk: DigiKeyClient,
+    mu: MouserClient,
+    fa: FarnellClient,
+    rs: RSClient,
+) -> PartResult:
+    cached = cache.get(manufacturer, mpn)
+    if cached:
+        log.debug(f"  cache hit: {mpn}")
+        return PartResult(
+            manufacturer=manufacturer,
+            mpn=mpn,
+            digikey_eur=cached.get("digikey_eur"),
+            mouser_eur=cached.get("mouser_eur"),
+            farnell_eur=cached.get("farnell_eur"),
+            rs_eur=cached.get("rs_eur"),
+        )
+
+    result = PartResult(manufacturer=manufacturer, mpn=mpn)
+    result.digikey_eur = dk.get_price_eur(manufacturer, mpn);  time.sleep(REQUEST_DELAY)
+    result.mouser_eur  = mu.get_price_eur(manufacturer, mpn);  time.sleep(REQUEST_DELAY)
+    result.farnell_eur = fa.get_price_eur(manufacturer, mpn);  time.sleep(REQUEST_DELAY)
+    result.rs_eur      = rs.get_price_eur(manufacturer, mpn)
+
+    cache.put(manufacturer, mpn, {
+        "digikey_eur": result.digikey_eur,
+        "mouser_eur":  result.mouser_eur,
+        "farnell_eur": result.farnell_eur,
+        "rs_eur":      result.rs_eur,
+    })
+    return result
+
+
+# ── Write-back ─────────────────────────────────────────────────────────────────
+
+def _part_key(manufacturer: str, mpn: str) -> str:
+    return f"{manufacturer.strip().lower()}||{mpn.strip().lower()}"
+
+
+def write_back(
+    file_map: dict[Path, list[TableLocation]],
+    price_lookup: dict[str, Optional[float]],
+) -> None:
+    """
+    Write the average EUR price at qty 1000 back into each BoM file.
+
+    For every component table:
+      - Adds a "Unit Cost 1000x Data" column header after the last existing
+        header in the table's header row (if the column doesn't exist already).
+      - Writes the price into each data row where the cell is currently empty.
+        Cells that already contain a value are left unchanged.
+    """
+    for file_path, tables in file_map.items():
+        log.info(f"Updating {file_path.name}")
+        try:
+            wb = openpyxl.load_workbook(file_path)
+        except Exception as exc:
+            log.error(f"  Cannot open {file_path.name} for writing: {exc}")
+            continue
+
+        for table in tables:
+            ws = wb[table.sheet_name]
+
+            # ── Find or create the "Unit Cost 1000x Data" column ──────────────
+            cost_col: Optional[int] = None
+            last_used_col = 1
+            max_col = ws.max_column or 1
+
+            for c in range(1, max_col + 1):
+                val = ws.cell(table.header_row, c).value
+                if val is not None:
+                    last_used_col = c
+                    if str(val).strip().lower() == COST_HEADER.lower():
+                        cost_col = c
+
+            if cost_col is None:
+                cost_col = last_used_col + 1
+                ws.cell(table.header_row, cost_col).value = COST_HEADER
+
+            # ── Fill prices for empty cells ───────────────────────────────────
+            filled  = 0
+            skipped = 0
+            for row_num, mfr, mpn in table.data:
+                cell = ws.cell(row_num, cost_col)
+                existing = cell.value
+                if existing is not None and str(existing).strip() != "":
+                    skipped += 1
+                    continue
+                price = price_lookup.get(_part_key(mfr, mpn))
+                if price is not None:
+                    cell.value = price
+                    filled += 1
+
+            log.info(
+                f"  Sheet '{table.sheet_name}' (header row {table.header_row}): "
+                f"{filled} filled, {skipped} skipped (already had a value)"
+            )
+
+        try:
+            wb.save(file_path)
+            log.info(f"  Saved  {file_path.name}")
+        except PermissionError:
+            log.error(
+                f"  Cannot save {file_path.name} – close the file in Excel first."
+            )
+        except Exception as exc:
+            log.error(f"  Save failed for {file_path.name}: {exc}")
+
+
+# ── Main ───────────────────────────────────────────────────────────────────────
+
+def main() -> None:
+    if not BOM_DIR.exists():
+        log.error(f"BoM directory '{BOM_DIR}' does not exist.")
+        sys.exit(1)
+
+    dk = DigiKeyClient()
+    mu = MouserClient()
+    fa = FarnellClient()
+    rs = RSClient()
+
+    active = [n for n, c in [("DigiKey", dk), ("Mouser", mu), ("Farnell", fa), ("RS", rs)]
+              if c.configured]
+    if active:
+        log.info(f"Configured APIs: {', '.join(active)}")
+    else:
+        log.warning("No API keys found.  Copy .env.example → .env and fill in your keys.")
+
+    file_map, parts = extract_parts(BOM_DIR)
+
+    if not parts:
+        log.error("No valid (Manufacturer, MPN) pairs found in BoM files.")
+        sys.exit(1)
+
+    cache = PriceCache(CACHE_FILE)
+    price_lookup: dict[str, Optional[float]] = {}
+
+    total = len(parts)
+    for i, (mfr, mpn) in enumerate(sorted(parts), 1):
+        log.info(f"[{i:>4}/{total}]  {mfr or '(no mfr)':35s}  {mpn}")
+        r = lookup(mfr, mpn, cache, dk, mu, fa, rs)
+        tag = f"€{r.average_eur:.4f}" if r.average_eur is not None else "—"
+        log.info(f"          avg {tag}  ({r.sources_found()}/4 sources)")
+        price_lookup[_part_key(mfr, mpn)] = r.average_eur
+
+    write_back(file_map, price_lookup)
+
+    found   = sum(1 for v in price_lookup.values() if v is not None)
+    missing = [mpn for (_, mpn), v in
+               ((k.split("||", 1), v) for k, v in price_lookup.items())
+               if v is None]
+    log.info(f"Done – pricing found for {found}/{total} unique parts.")
+    if missing:
+        sample = ", ".join(missing[:15])
+        tail   = f" … (+{len(missing) - 15} more)" if len(missing) > 15 else ""
+        log.info(f"No pricing found for: {sample}{tail}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..337ed98
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,4 @@
+requests>=2.31.0
+openpyxl>=3.1.0
+pandas>=2.0.0
+python-dotenv>=1.0.0