Phone Number Validation in Python — Beyond Regex

# app.py (Flask)
import os
from flask import Flask, request, jsonify
from isvalid_sdk import IsValidConfig, create_client

app = Flask(__name__)
iv = create_client(IsValidConfig(api_key=os.environ["ISVALID_API_KEY"]))


@app.post("/api/validate-phone")
def validate_phone_endpoint():
    """Validate a phone number and return parsed details."""
    body = request.get_json(silent=True) or {}
    phone = body.get("phone", "").strip()
    country = body.get("countryCode")

    if not phone:
        return jsonify({"error": "Phone number is required"}), 400

    try:
        if country:
            result = iv.phone(phone, country_code=country)
        else:
            result = iv.phone(phone)
    except Exception as exc:
        app.logger.error("Phone validation failed: %s", exc)
        return jsonify({"error": "Validation service unavailable"}), 502

    if not result["valid"]:
        return jsonify({
            "error": "Invalid phone number. Please check the number and try again.",
        }), 400

    return jsonify({
        "valid": True,
        "e164": result["e164"],
        "national": result["national"],
        "international": result["international"],
        "countryCode": result["countryCode"],
        "type": result["type"],
    })


@app.post("/api/register")
def register():
    """Registration endpoint with phone validation."""
    body = request.get_json(silent=True) or {}
    phone = body.get("phone", "").strip()
    name = body.get("name", "").strip()

    if not phone or not name:
        return jsonify({"error": "Name and phone are required"}), 400

    try:
        result = iv.phone(phone)
    except Exception:
        return jsonify({"error": "Phone validation service unavailable"}), 502

    if not result["valid"]:
        return jsonify({"error": "Invalid phone number"}), 400

    # Only accept mobile numbers for SMS verification
    if result.get("type") != "MOBILE":
        return jsonify({
            "error": "Please provide a mobile number for SMS verification.",
            "detectedType": result.get("type"),
        }), 400

    # Store the E.164-normalised number
    create_user(name=name, phone=result["e164"])
    return jsonify({"success": True, "phone": result["e164"]})

# batch_validate.py
import csv
import os
import sys
from isvalid_sdk import IsValidConfig, create_client

iv = create_client(IsValidConfig(api_key=os.environ["ISVALID_API_KEY"]))


def validate_csv(input_path: str, output_path: str) -> None:
    """Read phone numbers from a CSV, validate each, write results."""
    with open(input_path, newline="") as infile, \
         open(output_path, "w", newline="") as outfile:

        reader = csv.DictReader(infile)
        fieldnames = [
            "original", "valid", "e164", "country",
            "type", "national", "international",
        ]
        writer = csv.DictWriter(outfile, fieldnames=fieldnames)
        writer.writeheader()

        for row in reader:
            phone = row.get("phone", "").strip()
            if not phone:
                continue

            try:
                result = iv.phone(phone)
            except Exception as exc:
                print(f"Error validating {phone}: {exc}", file=sys.stderr)
                writer.writerow({"original": phone, "valid": False})
                continue

            writer.writerow({
                "original": phone,
                "valid": result["valid"],
                "e164": result.get("e164", ""),
                "country": result.get("countryCode", ""),
                "type": result.get("type", ""),
                "national": result.get("national", ""),
                "international": result.get("international", ""),
            })


if __name__ == "__main__":
    validate_csv("contacts.csv", "validated_contacts.csv")
    print("Done. Results written to validated_contacts.csv")