diff --git a/api/__init__.py b/api/__init__.py
index 0854a57..9ea241c 100644
--- a/api/__init__.py
+++ b/api/__init__.py
@@ -4,7 +4,7 @@ from .project import copy_project
 
 from .operation import execute_undo as undo
 from .operation import execute_redo as redo
-from .operation import take_snapshot, pick_snapshot
+from .operation import have_snapshot, take_snapshot, pick_snapshot
 from .operation import have_transaction, start_transaction, commit_transaction, rollback_transaction
 
 from .s0_base import is_node, is_junction, is_reservoir, is_tank
diff --git a/api/operation.py b/api/operation.py
index b2d8ccd..969362f 100644
--- a/api/operation.py
+++ b/api/operation.py
@@ -119,6 +119,11 @@ def execute_redo(name: str) -> None:
 # snapshot is persistent
 # since redo always remember the recently undo path
 
+def have_snapshot(name: str, tag: str) -> bool:
+    with conn[name].cursor(row_factory=dict_row) as cur:
+        cur.execute(f"select id from snapshot_operation where tag = '{tag}'")
+        return cur.rowcount > 0
+
 def take_snapshot(name: str, tag: str) -> None:
     if tag == None or tag == '':
         print('Non empty tag is expected!')
@@ -127,7 +132,6 @@ def take_snapshot(name: str, tag: str) -> None:
     curr = _get_current_operation(name)
 
     with conn[name].cursor() as cur:
-        parent = _get_current_operation(name)
         cur.execute(f"insert into snapshot_operation (id, tag) values ({curr}, '{tag}')")
 
 def pick_snapshot(name: str, tag: str) -> None:
@@ -135,14 +139,15 @@ def pick_snapshot(name: str, tag: str) -> None:
         print('Non empty tag is expected!')
         return
 
+    if not have_snapshot(name, tag):
+        print('No such snapshot!')
+        return
+
     curr = _get_current_operation(name)
     curr_parents = _get_parents(name, curr)
 
     with conn[name].cursor(row_factory=dict_row) as cur:
         cur.execute(f"select id from snapshot_operation where tag = '{tag}'")
-        if cur.rowcount < 1:
-            print('No such snapshot!')
-            return
         target = int(cur.fetchone()['id'])
         if target in curr_parents: # target -> curr
             for i in range(curr_parents.index(target)):
diff --git a/tjnetwork_new.py b/tjnetwork_new.py
index 52cb0e5..005292a 100644
--- a/tjnetwork_new.py
+++ b/tjnetwork_new.py
@@ -49,6 +49,9 @@ def undo(name: str) -> None:
 def redo(name: str) -> None:
     return api.redo(name)
 
+def have_snapshot(name: str, tag: str) -> None:
+    return api.have_snapshot(name, tag)
+
 def take_snapshot(name: str, tag: str) -> None:
     return api.take_snapshot(name, tag)