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Solutions/8_1/follow.py

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+# follow.py
+import os
+import time
+
+def follow(filename):
+    '''
+    Generator that produces a sequence of lines being written at the end of a file.
+    '''
+    with open(filename,'r') as f:
+        f.seek(0,os.SEEK_END)
+        while True:
+             line = f.readline()
+             if line == '':
+                 time.sleep(0.1)    # Sleep briefly to avoid busy wait
+                 continue
+             yield line
+
+# Example use
+if __name__ == '__main__':
+    for line in follow('../../Data/stocklog.csv'):
+        fields = line.split(',')
+        name = fields[0].strip('"')
+        price = float(fields[1])
+        change = float(fields[4])
+        if change < 0:
+            print('%10s %10.2f %10.2f' % (name, price, change))
+