How to Validate BIC / SWIFT Codes in Python

import re

# ❌ Structurally correct — but misses real-world edge cases
BIC_REGEX = re.compile(
    r'^[A-Z]{4}'   # institution (4 letters)
    r'[A-Z]{2}'    # country (2 letters)
    r'[A-Z0-9]{2}' # location (2 alphanumeric)
    r'([A-Z0-9]{3})?$'  # optional branch (3 alphanumeric)
)

def validate_bic_naive(bic: str) -> bool:
    return bool(BIC_REGEX.match(bic.upper().strip()))

print(validate_bic_naive("DEUTDEDB"))      # True  ✓
print(validate_bic_naive("DEUTDEDBXXX"))   # True  ✓
print(validate_bic_naive("DEUTDEDBBER"))   # True  ✓
print(validate_bic_naive("AAAABB11"))      # True  ✗ — structurally valid but not a real institution
print(validate_bic_naive("DEUTDEDE"))      # True  ✗ — technically valid format, may not exist
print(validate_bic_naive("DEUTDE"))        # False ✓ — too short

# bic_validator.py
import os
import requests

API_KEY = os.environ["ISVALID_API_KEY"]
BASE_URL = "https://api.isvalid.dev"


def validate_bic(bic: str) -> dict:
    """
    Validate a BIC/SWIFT code using the IsValid API.

    Returns a dict with keys: valid, bankCode, countryCode, countryName,
    locationCode, branchCode, bankName, city, branch.
    Raises requests.HTTPError on non-2xx responses.
    """
    response = requests.get(
        f"{BASE_URL}/v0/bic",
        params={"value": bic},
        headers={"Authorization": f"Bearer {API_KEY}"},
        timeout=5,
    )
    response.raise_for_status()
    return response.json()


# ── Example usage ─────────────────────────────────────────────────────────────

if __name__ == "__main__":
    result = validate_bic("DEUTDEDBBER")

    if not result["valid"]:
        print("Invalid BIC")
    else:
        bank = result.get("bankName") or result["bankCode"]
        country = result.get("countryName") or result["countryCode"]
        city = result.get("city") or "—"
        branch = result.get("branch") or "primary office"
        print(f"{bank} · {country} · {city} · {branch}")
        # → Deutsche Bank · Germany · Berlin · Berlin

# bic_validator_stdlib.py
import json
import os
import urllib.error
import urllib.parse
import urllib.request


API_KEY = os.environ["ISVALID_API_KEY"]
BASE_URL = "https://api.isvalid.dev"


def validate_bic(bic: str) -> dict:
    params = urllib.parse.urlencode({"value": bic})
    url = f"{BASE_URL}/v0/bic?{params}"

    req = urllib.request.Request(
        url,
        headers={"Authorization": f"Bearer {API_KEY}"},
    )

    try:
        with urllib.request.urlopen(req, timeout=5) as resp:
            return json.loads(resp.read().decode())
    except urllib.error.HTTPError as exc:
        body = exc.read().decode()
        raise RuntimeError(f"API error {exc.code}: {body}") from exc


# ── Batch validation ──────────────────────────────────────────────────────────

def validate_bics(bic_list: list[str]) -> list[dict]:
    """Validate multiple BICs, returning results in order."""
    results = []
    for bic in bic_list:
        try:
            results.append({"bic": bic, **validate_bic(bic)})
        except RuntimeError as exc:
            results.append({"bic": bic, "valid": False, "error": str(exc)})
    return results


if __name__ == "__main__":
    codes = ["DEUTDEDBBER", "BNPAFRPPXXX", "CHASUS33", "INVALID123"]
    for r in validate_bics(codes):
        status = "✓" if r.get("valid") else "✗"
        name = r.get("bankName") or "unknown"
        print(f"  {status}  {r['bic']:<15}  {name}")

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/bic?value=DEUTDEDBBER"

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/bic?value=DEUTDEDB"

curl -H "Authorization: Bearer YOUR_API_KEY" \
  "https://api.isvalid.dev/v0/bic?value=TOOSHORT"

{
  "valid": true,
  "bankCode": "XASX",
  "countryCode": "AU",
  "countryName": "Australia",
  "locationCode": "2S",
  "branchCode": "RTG",
  "bankName": "ASX Operations Pty Limited",
  "city": "Sydney",
  "branch": "RTGS Settlement"
}

{
  "valid": true,
  "bankCode": "BNPA",
  "countryCode": "FR",
  "countryName": "France",
  "locationCode": "PP",
  "branchCode": null,
  "bankName": "BNP Paribas",
  "city": "Paris",
  "branch": null
}

{
  "valid": false,
  "bankCode": "TOOS",
  "countryCode": "HO",
  "countryName": null,
  "locationCode": "RT",
  "branchCode": null,
  "bankName": null,
  "city": null,
  "branch": null
}