diff --git a/format.sh b/format.sh
new file mode 100755
index 00000000000..77f3719323f
--- /dev/null
+++ b/format.sh
@@ -0,0 +1,3 @@
+#!/bin/bash
+
+python3 -m black .
diff --git a/oracle.py b/oracle.py
index bd035139b63..e3af0041776 100644
--- a/oracle.py
+++ b/oracle.py
@@ -235,14 +235,11 @@ def check_status(learning_status, testing_status):
             for attr in learning_status[rtype]:
                 if learning_status[rtype][attr] != testing_status[rtype][attr]:
                     alarm += 1
-                    bug_report += (
-                        "[ERROR] %s %s inconsistency: %s seen after learning run, but %s seen after testing run\n"
-                        % (
-                            rtype,
-                            attr.upper(),
-                            str(learning_status[rtype][attr]),
-                            str(testing_status[rtype][attr]),
-                        )
+                    bug_report += "[ERROR] %s %s inconsistency: %s seen after learning run, but %s seen after testing run\n" % (
+                        rtype,
+                        attr.upper(),
+                        str(learning_status[rtype][attr]),
+                        str(testing_status[rtype][attr]),
                     )
     final_bug_report = (
         "Liveness assertion failed:\n" + bug_report if bug_report != "" else ""
@@ -328,16 +325,13 @@ def check_side_effect(
                         continue
                 if learning_entry[attr] != testing_entry[attr]:
                     alarm += 1
-                    bug_report += (
-                        "[ERROR] %s/%s/%s %s inconsistency: %s events seen during learning run, but %s seen during testing run\n"
-                        % (
-                            rtype,
-                            namespace,
-                            name,
-                            attr.upper(),
-                            str(learning_entry[attr]),
-                            str(testing_entry[attr]),
-                        )
+                    bug_report += "[ERROR] %s/%s/%s %s inconsistency: %s events seen during learning run, but %s seen during testing run\n" % (
+                        rtype,
+                        namespace,
+                        name,
+                        attr.upper(),
+                        str(learning_entry[attr]),
+                        str(testing_entry[attr]),
                     )
     final_bug_report = (
         "Safety assertion failed:\n" + bug_report if bug_report != "" else ""
@@ -346,34 +340,28 @@ def check_side_effect(
 
 
 def generate_time_travel_debugging_hint(testing_config):
-    desc = (
-        "Sieve makes the controller time travel back to the history to see the status just %s %s: %s"
-        % (
-            testing_config["timing"],
-            testing_config["ce-rtype"]
-            + "/"
-            + testing_config["ce-namespace"]
-            + "/"
-            + testing_config["ce-name"],
-            testing_config["ce-diff-current"],
-        )
+    desc = "Sieve makes the controller time travel back to the history to see the status just %s %s: %s" % (
+        testing_config["timing"],
+        testing_config["ce-rtype"]
+        + "/"
+        + testing_config["ce-namespace"]
+        + "/"
+        + testing_config["ce-name"],
+        testing_config["ce-diff-current"],
     )
-    suggestion = (
-        "Please check how controller reacts when seeing %s: %s, the controller might issue %s to %s without proper checking"
-        % (
-            testing_config["ce-rtype"]
-            + "/"
-            + testing_config["ce-namespace"]
-            + "/"
-            + testing_config["ce-name"],
-            testing_config["ce-diff-current"],
-            "deletion" if testing_config["se-etype"] == "ADDED" else "creation",
-            testing_config["se-rtype"]
-            + "/"
-            + testing_config["se-namespace"]
-            + "/"
-            + testing_config["se-name"],
-        )
+    suggestion = "Please check how controller reacts when seeing %s: %s, the controller might issue %s to %s without proper checking" % (
+        testing_config["ce-rtype"]
+        + "/"
+        + testing_config["ce-namespace"]
+        + "/"
+        + testing_config["ce-name"],
+        testing_config["ce-diff-current"],
+        "deletion" if testing_config["se-etype"] == "ADDED" else "creation",
+        testing_config["se-rtype"]
+        + "/"
+        + testing_config["se-namespace"]
+        + "/"
+        + testing_config["se-name"],
     )
     return desc + "\n" + suggestion + "\n"
 
@@ -387,16 +375,13 @@ def generate_obs_gap_debugging_hint(testing_config):
         + testing_config["ce-name"],
         testing_config["ce-diff-current"],
     )
-    suggestion = (
-        "Please check how controller reacts when seeing %s: %s, the event can trigger a controller side effect, and it might be cancelled by following events"
-        % (
-            testing_config["ce-rtype"]
-            + "/"
-            + testing_config["ce-namespace"]
-            + "/"
-            + testing_config["ce-name"],
-            testing_config["ce-diff-current"],
-        )
+    suggestion = "Please check how controller reacts when seeing %s: %s, the event can trigger a controller side effect, and it might be cancelled by following events" % (
+        testing_config["ce-rtype"]
+        + "/"
+        + testing_config["ce-namespace"]
+        + "/"
+        + testing_config["ce-name"],
+        testing_config["ce-diff-current"],
     )
     return desc + "\n" + suggestion + "\n"
 
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 00000000000..3f735f03451
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,21 @@
+[tool.black]
+line-length = 88
+target-version = ['py36']
+include = '\.pyi?$'
+exclude = '''
+  /(
+      \.eggs         # exclude a few common directories in the
+    | \.git          # root of the project
+    | \.hg
+    | \.mypy_cache
+    | \.tox
+    | \.venv
+    | _build
+    | buck-out
+    | build
+    | dist
+    | fakegopath
+    | log
+    | app
+  )/
+'''
diff --git a/sieve.py b/sieve.py
index 1508f0d4e4c..09e5ba949fa 100644
--- a/sieve.py
+++ b/sieve.py
@@ -664,14 +664,18 @@ def run_batch(project, test, dir, mode, stage, docker):
         sieve_modes.OBS_GAP,
         sieve_modes.ATOM_VIO,
         "learn",
-    ], ("invalid mode option: %s" % options.mode)
+    ], (
+        "invalid mode option: %s" % options.mode
+    )
     assert options.phase in [
         "all",
         "setup_only",
         "workload_only",
         "check_only",
         "workload_and_check",
-    ], ("invalid phase option: %s" % options.phase)
+    ], (
+        "invalid phase option: %s" % options.phase
+    )
 
     print("Running Sieve with %s: %s..." % (options.stage, options.mode))