UP my solution

numpy_questions.py

@@ -2,8 +2,8 @@
 
 The goals of this assignment are:
     * Use numpy in practice with two easy exercises.
-    * Use automated tools to validate the code (`pytest` and `flake8`)
-    * Submit a Pull-Request on github to practice `git`.
+    * Use automated tools to validate the code (`pytest` and `flake8`).
+    * Submit a Pull-Request on GitHub to practice `git`.
 
 The two functions below are skeleton functions. The docstrings explain what
 are the inputs, the outputs and the expected error. Fill the function to
@@ -29,19 +29,19 @@ def max_index(X):
     Returns
     -------
     (i, j) : tuple(int)
-        The row and columnd index of the maximum.
+        The row and column index of the maximum.
 
     Raises
     ------
     ValueError
         If the input is not a numpy array or
         if the shape is not 2D.
     """
-    i = 0
-    j = 0
-
-    # TODO
-
+    if not isinstance(X, np.ndarray):
+        raise ValueError("X must be a numpy array (np.ndarray).")
+    if len(X.shape) != 2:
+        raise ValueError("X must be a 2D array.")
+    i, j = np.unravel_index(np.argmax(X), X.shape)
     return i, j
 
 
@@ -62,6 +62,9 @@ def wallis_product(n_terms):
     pi : float
         The approximation of order `n_terms` of pi using the Wallis product.
     """
-    # XXX : The n_terms is an int that corresponds to the number of
-    # terms in the product. For example 10000.
-    return 0.
+    if n_terms == 0:
+        return 2
+    s = 4 / 3
+    for i in range(2, n_terms + 1):
+        s *= 4 * i**2 / (4 * i**2 - 1)
+    return s * 2