feat: export wallet address (#48)

* first pass implementing wallet address private key export as a hex string

* formatting

* implementing feedback

* adding additional check for key bytes

---------

Co-authored-by: Christopher Gerber <christopher.gerber@coinbase.com>

Author: stat

cdp/wallet_address.py

@@ -72,6 +72,26 @@ def can_sign(self) -> bool:
         """
         return self.key is not None
 
+    def export(self) -> str:
+        """Export the wallet address's private key as a hex string.
+
+        Returns:
+            str: The wallet address's private key as a hex string.
+
+        Raises:
+            ValueError: If the wallet address does not have a private key.
+
+        """
+        local_account = self.key
+        if local_account is None:
+            raise ValueError("Private key is unavailable")
+
+        key_bytes = local_account.key
+        if key_bytes is None:
+            raise ValueError("Private key is empty")
+
+        return key_bytes.hex()
+
     def transfer(
         self,
         amount: Number | Decimal | str,

tests/test_wallet_address.py

@@ -81,6 +81,25 @@ def test_key_setter_raises_error_when_already_set(wallet_address_factory):
         wallet_address_with_key.key = new_key
 
 
+def test_export(wallet_address_factory):
+    """Test export method success for a WalletAddress."""
+    wallet_address_with_key = wallet_address_factory(True)
+
+    key_hex = wallet_address_with_key.export()
+
+    assert key_hex is not None
+    assert key_hex != ""
+    assert key_hex.startswith("0x")
+
+
+def test_export_raises_error_when_local_account_is_none(wallet_address_factory):
+    """Test export method failure for a WalletAddress with no LocalAccount."""
+    wallet_address_without_key = wallet_address_factory()
+
+    with pytest.raises(ValueError, match="Private key is unavailable"):
+        wallet_address_without_key.export()
+
+
 @patch("cdp.wallet_address.Transfer")
 @patch("cdp.Cdp.api_clients")
 @patch("cdp.Cdp.use_server_signer", True)