Add slides and samples for session 3

Author: lumbric

session3_scientific_ecosystem/code-samples/slow_average.py

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+"""
+A dummy script which could run much faster.
+
+Try to profile it, find bad design and correct it!
+
+"""
+
+import logging
+import numpy as np
+from itertools import product
+from collections import namedtuple
+from contexttimer import timer
+
+
+# will be modified, this is is not thread safe!
+cache = namedtuple('keys', 'values')
+cache.keys = []
+cache.values = []
+
+
+def read_wind_speed(time, location_x, location_y):
+    """Read wind speed value at location x/y and time from fancy database."""
+    key = time, location_x, location_y
+    if key in cache.keys:
+        idx = cache.keys.index(key)
+        return cache.values[idx]
+
+    # imagine that this is downloaded from some database:
+    value = np.random.random()
+
+    # cache it for next time!
+    cache.keys.append(key)
+    cache.values.append(value)
+
+    return value
+
+
+@timer()
+def main():
+    times = np.arange(100)
+    locations_x = np.arange(15)
+    locations_y = np.arange(18)
+
+    values = [read_wind_speed(t, x, y)
+              for t, x, y in product(times, locations_x, locations_y)]
+
+    print(sum(values) / len(values))
+
+
+if __name__ == '__main__':
+    logging.basicConfig(level=logging.INFO)
+    main()