HTTP request failed: 401 Client Error: Unauthorized for url error while integrating netsuite using python

Question

I am trying to integrate netsuite using python. I am using oauth autentication and the credentials are working fine in postman. However I am getting the below error in python

HTTP request failed: 401 Client Error: Unauthorized for url

Code:

    import requests
    import time
    import uuid
    import hashlib
    import hmac
    import base64
    from urllib.parse import quote
    from requests_oauthlib import OAuth1Session
    
    
    ACCOUNT_ID = 'YOUR_ACCOUNT_ID'  # Your NetSuite account ID (e.g., 123456_SB1)
    CONSUMER_KEY = 'YOUR_CONSUMER_KEY'  # Consumer Key from Integration record
    CONSUMER_SECRET = 'YOUR_CONSUMER_SECRET'  # Consumer Secret from Integration record
    TOKEN_ID = 'YOUR_TOKEN_ID'  # Token ID from Access Token
    TOKEN_SECRET = 'YOUR_TOKEN_SECRET'  # Token Secret from Access Token
    NETSUITE_BASE_URL = f"https://{ACCOUNT_ID.lower()}.suitetalk.api.netsuite.com"
    
    # REST API Endpoint for Purchase Orders
    PURCHASE_ORDERS_ENDPOINT = f"{NETSUITE_BASE_URL}/services/rest/record/v1/purchaseOrder"
    
    def generate_oauth_header(url, method="GET"):
        """
        Generates an OAuth 1.0 header for NetSuite API requests.
        """
        # OAuth parameters
        oauth_nonce = str(uuid.uuid4().hex)
        oauth_timestamp = str(int(time.time()))
        oauth_signature_method = "HMAC-SHA256"
        oauth_version = "1.0"
    
        # Base string for the signature
        base_string = f"{method.upper()}&{quote(url, safe='')}&"
        params = {
            "realm": ACCOUNT_ID,
            "oauth_consumer_key": CONSUMER_KEY,
            "oauth_token": TOKEN_ID,
            "oauth_nonce": oauth_nonce,
            "oauth_timestamp": oauth_timestamp,
            "oauth_signature_method": oauth_signature_method,
            "oauth_version": oauth_version,
        }
        encoded_params = "&".join(f"{quote(k, safe='')}={quote(v, safe='')}" for k, v in sorted(params.items()))
        base_string += quote(encoded_params, safe='')
        print("\nBase String for Signature:")
        print(base_string)
        # Signing key
        signing_key = f"{quote(CONSUMER_SECRET, safe='')}&{quote(TOKEN_SECRET, safe='')}"
    
        # Generate signature
        hashed = hmac.new(signing_key.encode('utf-8'), base_string.encode('utf-8'), hashlib.sha256)
        oauth_signature = base64.b64encode(hashed.digest()).decode()
    
        # Add signature to params
        params["oauth_signature"] = oauth_signature
    
        # Build the Authorization header
        oauth_header = "OAuth " + ", ".join(f'{quote(k)}="{quote(v)}"' for k, v in params.items())
        print("OAuth Authorization Header:")
        print(oauth_header)
        return oauth_header
    
    def fetch_purchase_orders():
        """
        Fetches a list of purchase orders from NetSuite using custom OAuth header.
        """
        try:
            # Generate OAuth header
            oauth_header = generate_oauth_header(PURCHASE_ORDERS_ENDPOINT, method="GET")
            headers = {
                "Authorization": oauth_header,
                "Content-Type": "application/json",
                "Prefer": "transient"  # Optional: For performance, avoid caching
            }
    
            # Make the GET request
            response = requests.get(PURCHASE_ORDERS_ENDPOINT, headers=headers)
            response.raise_for_status()
    
            # Parse and print the response
            data = response.json()
            purchase_orders = data.get('items', [])
            if not purchase_orders:
                print("No purchase orders found.")
            else:
                for po in purchase_orders:
                    print(f"PO ID: {po['id']}, Vendor: {po.get('entity', {}).get('refName')}, Total: {po.get('total')}")
    
    
        except requests.exceptions.RequestException as e:
            print(f"HTTP request failed: {e}")
        except Exception as e:
            print(f"An unexpected error occurred: {e}")
    
    
    if __name__ == "__main__":
        fetch_purchase_orders()