add week 3

Week 01/Python review session/python-review-demo.py

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+import numpy as np
+
+def power_iteration(A, tolerance=1e-7):
+    b_old = np.random.rand(A.shape[1])
+    b = np.random.rand(A.shape[1])
+    num_iterations = 0
+    while num_iterations == 0 or np.linalg.norm(b_old - b) > tolerance:
+        b_old = np.copy(b)
+        b = np.dot(A, b)
+        b_norm = np.linalg.norm(b)
+        b /= b_norm
+        num_iterations += 1
+    return np.dot(A, b), b, num_iterations
+
+def main():
+    A = np.array([[.5, .4], [.2, .8]])
+    ab, b, number_iterations = power_iteration(A)
+
+    eig1 = ab[0] / b[0]
+    eig2 = ab[1] / b[1]
+    assert(np.abs((eig1 - eig2) / eig2) < 1e-5)
+
+    b /= b[1]
+
+    print(eig1, b, number_iterations)
+
+if __name__ == '__main__':
+    main()

Week 03/Assignment 3/README.md

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+# Assignment 3
+
+- [Handout](http://web.stanford.edu/class/cs224n/assignments/a3.pdf)

Week 03/Assignment 3/collect_submission.sh

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+rm -f assignment3.zip
+zip -r assignment3.zip *.py ./data ./utils