Why

.editorconfig

+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = true

__main__.py

+# t = minimum degree
+# minimum of t-1 keys for every node except root
+# 2t - 1 keys at most for every node
+
+
+class Node:
+    def __init__(self, t):
+        self.t = t
+        self.keys = []
+        self.children = []
+        self.is_leaf = False
+
+
+def insert(t, root, key):
+    if root is None:
+        root = Node(t)
+        root.keys = [key]
+        root.is_leaf = True
+        return root
+    insert_index = -1
+    for i in range(len(root.keys)):
+        if key < root.keys[i]:
+            insert_index = i
+            break
+        if i == len(root.keys) - 1:
+            insert_index = i + 1
+            break
+    if root.is_leaf and len(root.keys) == 2 * root.t - 1:
+        parent = Node(root.t)
+        parent.children = [root]
+        split_child(parent, 0)
+        return parent
+        # parent = Node(root.t)
+        # root.keys.insert(insert_index, key)
+        # left = root
+        # right = Node(root.t)
+        # split_index = len(root.keys) // 2
+        # right.keys = root.keys[split_index:]
+        # left.keys = root.keys[:split_index]
+        # parent.keys = [right.keys[0]]
+        # parent.children = [left, right]
+    if root.is_leaf:
+        root.keys.insert(insert_index, key)
+        return root
+
+def split_child(root, i):
+    left = root.children[i]
+    split_index = len(root.keys) // 2 + 1
+    right = Node(root.t)
+    right.keys = left.keys[split_index:]
+    left.keys = left.keys[:split_index]
+    root.children = [left, right]
+    root.keys = [right.keys[0]]
+
+
+def main():
+    t = 2
+    root = None
+    root = insert(t, root, 20)
+    root = insert(t, root, 40)
+    root = insert(t, root, 5)
+    root = insert(t, root, 3)
+    print(root.keys)
+    print(root.children[0].keys)
+    print(root.children[1].keys)
+
+
+if __name__ == "__main__":
+    main()