added butterfy_pattern under strings folder

Author: Medha

strings/butterfly_pattern.py

@@ -0,0 +1,37 @@
+def print_butterfly(n: int) -> None:
+    """
+    Prints a butterfly pattern using the character '*' based on the input size.
+
+    The butterfly pattern has a symmetrical structure with an upper and lower half.
+
+    :param n: The size of the butterfly (side length).
+    :return: None
+
+    Example:
+    >>> print_butterfly(5)
+    *       *
+    **     **
+    ***   ***
+    **** ****
+    *********
+    **** ****
+    ***   ***
+    **     **
+    *       *
+    """
+    # Upper half of the butterfly
+    for i in range(1, n + 1):
+        print("*" * i, end="")
+        print(" " * (2 * (n - i)), end="")
+        print("*" * i)
+
+    # Lower half of the butterfly
+    for i in range(n, 0, -1):
+        print("*" * i, end="")
+        print(" " * (2 * (n - i)), end="")
+        print("*" * i)
+
+
+# Ask the user for input and print the butterfly
+n = int(input("Enter the value of n: "))
+print_butterfly(n)