UP my solution

Author: Youna Maillie

numpy_questions.py

@@ -37,11 +37,17 @@ def max_index(X):
         If the input is not a numpy array or
         if the shape is not 2D.
     """
-    i = 0
-    j = 0
+    # Test if the input is a numpy array or not
+    if not isinstance(X, np.ndarray):
+        raise ValueError("Input is not a numpy array.")
 
-    # TODO
+    # Test if the input is in 2D
+    if X.ndim != 2:
+        raise ValueError("Input array is not in 2D.")
 
+    # Return the index tupple corresponding
+    # to the maximum in the input numpy array
+    i, j = np.unravel_index(np.argmax(X), X.shape)
     return i, j
 
 
@@ -64,4 +70,15 @@ def wallis_product(n_terms):
     """
     # XXX : The n_terms is an int that corresponds to the number of
     # terms in the product. For example 10000.
-    return 0.
+    product = 1.0
+    if n_terms == 0:
+        return product * 2
+
+    for n in range(1, n_terms + 1):
+        numerator = 4 * n**2
+        denominator = numerator - 1
+        product *= numerator / denominator
+
+    pi_approx = 2*product
+
+    return pi_approx