Feature/clone txn (#106)

* add clone method to Txn

* add test for rxn.clone()

README.md

@@ -42,7 +42,7 @@ Notice: The authentication header through gRPC-JSON-Gateway only supported in [e
 
 **Install**
 ```bash
-$ pip install etcd3-py
+$ pip install --upgrade etcd3-py
 ```
 
 **Sync Client**

etcd3/stateful/transaction.py

@@ -55,9 +55,10 @@ def __init__(self, client, compare=None, success=None, failure=None):
         :param failure: failure components of the transaction, default to []
         """
         self.client = client
-        self._compare = compare or []
-        self._success = success or []
-        self._failure = failure or []
+        self._compare = list(compare or [])
+        self._success = list(success or [])
+        self._failure = list(failure or [])
+        self._committed = False
 
     def clear(self):  # pragma: no cover
         """
@@ -267,6 +268,20 @@ def delete(key=None, range_end=None, prev_kv=False, prefix=None, all=None):
         """
         return kv.delete_range(key=key, range_end=range_end, prev_kv=prev_kv, prefix=prefix, all=all, txn_obj=True)
 
+    def __copy__(self):
+        return Txn(
+            client=self.client,
+            compare=self._compare[:],
+            success=self._success[:],
+            failure=self._failure[:]
+        )
+
+    def clone(self):
+        """
+        :return: Txn
+        """
+        return self.__copy__()
+
 
 class TxnCompareOp(object):
     """

tests/test_transaction_util.py

@@ -110,3 +110,13 @@ def test_transaction(client):
     txn = client.Txn()
     r = txn.compare(txn.key('foo').lease == ID).commit()
     assert r.succeeded
+
+
+def test_txn_clone(client):
+    txn0 = client.Txn()
+    txn0.If(txn0.key('foo').value < b'1')
+    txn1 = txn0.clone()
+    assert id(txn0._compare) != id(txn1._compare)
+    txn0.Then(txn0.range('foo'))
+    assert len(txn0._success) == 1
+    assert len(txn1._success) == 0