Initial commit

Solutions/8_4/cofollow.py

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+# cofollow.py
+import os
+import time
+import csv
+
+def follow(filename,target):
+    with open(filename,"r") as f:
+        f.seek(0,os.SEEK_END)
+        while True:
+            line = f.readline()
+            if line != '':
+                target.send(line)
+            else:
+                time.sleep(0.1)
+
+# Decorator for coroutines
+from functools import wraps
+
+def consumer(func):
+    @wraps(func)
+    def start(*args,**kwargs):
+        f = func(*args,**kwargs)
+        f.send(None)
+        return f
+    return start
+
+# Sample coroutine
+@consumer
+def printer():
+    while True:
+        try:
+            item = yield
+            print(item)
+        except Exception as e:
+            print('ERROR: %r' % e)
+
+# Example use.  
+
+if __name__ == '__main__':
+    follow('../../Data/stocklog.csv', printer())

Solutions/8_4/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.
+    '''
+    try:
+        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
+    except GeneratorExit:
+        print('Following Done')
+
+def splitter(lines):
+    for line in lines:
+        yield line.split(',')
+
+
+def make_records(rows,names):
+    for row in rows:
+        yield dict(zip(names,row))
+
+def unquote(records,keylist):
+    for r in records:
+        for key in keylist:
+            r[key] = r[key].strip('"')
+        yield r
+
+def convert(records,converter,keylist):
+    for r in records:
+        for key in keylist:
+            r[key] = converter(r[key])
+        yield r
+
+def parse_stock_data(lines):
+    rows = splitter(lines)
+    records = make_records(rows,['name','price','date','time',
+                              'change','open','high','low','volume'])
+    records = unquote(records,["name","date","time"])
+    records = convert(records,float,['price','change','open','high','low'])
+    records = convert(records,int,['volume'])
+    return records
+
+# Sample use
+if __name__ == '__main__':
+   lines = follow("../../Data/stocklog.dat")
+   records = parse_stock_data(lines)
+   for r in records:
+       print("%(name)10s %(price)10.2f %(change)10.2f" % r)