Added solution code

Solutions/7_4/fileparse.py

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+# fileparse.py
+import csv
+
+def parse_csv(lines, select=None, types=None, has_headers=True, delimiter=',', silence_errors=False):
+    '''
+    Parse a CSV file into a list of records with type conversion.
+    '''
+    if select and not has_headers:
+        raise RuntimeError('select requires column headers')
+
+    rows = csv.reader(lines, delimiter=delimiter)
+
+    # Read the file headers (if any)
+    headers = next(rows) if has_headers else []
+
+    # If specific columns have been selected, make indices for filtering and set output columns
+    if select:
+        indices = [ headers.index(colname) for colname in select ]
+        headers = select
+
+    records = []
+    for rowno, row in enumerate(rows, 1):
+        if not row:     # Skip rows with no data
+            continue
+
+        # If specific column indices are selected, pick them out
+        if select:
+            row = [ row[index] for index in indices]
+
+        # Apply type conversion to the row
+        if types:
+            try:
+                row = [func(val) for func, val in zip(types, row)]
+            except ValueError as e:
+                if not silence_errors:
+                    print(f"Row {rowno}: Couldn't convert {row}")
+                    print(f"Row {rowno}: Reason {e}")
+                continue
+
+        # Make a dictionary or a tuple
+        if headers:
+            record = dict(zip(headers, row))
+        else:
+            record = tuple(row)
+        records.append(record)
+
+    return records

Solutions/7_4/follow.py

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+# follow.py
+
+import time
+import os
+
+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 != '':
+                 yield line
+             else:
+                 time.sleep(0.1)    # Sleep briefly to avoid busy wait

Solutions/7_4/pcost.py

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+# pcost.py
+
+import report
+
+def portfolio_cost(filename):
+    '''
+    Computes the total cost (shares*price) of a portfolio file
+    '''
+    portfolio = report.read_portfolio(filename)
+    return portfolio.total_cost
+
+def main(args):
+    if len(args) != 2:
+        raise SystemExit('Usage: %s portfoliofile' % args[0])
+    filename = args[1]
+    print('Total cost:', portfolio_cost(filename))
+
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)

Solutions/7_4/portfolio.py

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+# portfolio.py
+
+class Portfolio(object):
+    def __init__(self, holdings):
+        self._holdings = holdings
+
+    def __iter__(self):
+        return self._holdings.__iter__()
+
+    def __len__(self):
+        return len(self._holdings)
+
+    def __getitem__(self, index):
+        return self._holdings[index]
+
+    def __contains__(self, name):
+        return any(s.name == name for s in self._holdings)
+
+    @property
+    def total_cost(self):
+        return sum(s.shares * s.price for s in self._holdings)
+
+    def tabulate_shares(self):
+        from collections import Counter
+        total_shares = Counter()
+        for s in self._holdings:
+            total_shares[s.name] += s.shares
+        return total_shares
+
+
+        

Solutions/7_4/report.py

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+# report.py
+
+import fileparse
+from stock import Stock
+import tableformat
+from portfolio import Portfolio
+
+def read_portfolio(filename, **opts):
+    '''
+    Read a stock portfolio file into a list of dictionaries with keys
+    name, shares, and price.
+    '''
+    with open(filename) as lines:
+        portdicts = fileparse.parse_csv(lines, 
+                                        select=['name','shares','price'], 
+                                        types=[str,int,float],
+                                        **opts)
+
+    portfolio = [ Stock(**d) for d in portdicts ]
+    return Portfolio(portfolio)
+
+def read_prices(filename, **opts):
+    '''
+    Read a CSV file of price data into a dict mapping names to prices.
+    '''
+    with open(filename) as lines:
+        return dict(fileparse.parse_csv(lines,types=[str,float], has_headers=False, **opts))
+
+def make_report_data(portfolio, prices):
+    '''
+    Make a list of (name, shares, price, change) tuples given a portfolio list
+    and prices dictionary.
+    '''
+    rows = []
+    for s in portfolio:
+        current_price = prices[s.name]
+        change = current_price - s.price
+        summary = (s.name, s.shares, current_price, change)
+        rows.append(summary)
+    return rows
+
+def print_report(reportdata, formatter):
+    '''
+    Print a nicely formated table from a list of (name, shares, price, change) tuples.
+    '''
+    formatter.headings(['Name','Shares','Price','Change'])
+    for name, shares, price, change in reportdata:
+        rowdata = [ name, str(shares), f'{price:0.2f}', f'{change:0.2f}' ]
+        formatter.row(rowdata)
+
+def portfolio_report(portfoliofile, pricefile, fmt='txt'):
+    '''
+    Make a stock report given portfolio and price data files.
+    '''
+    # Read data files 
+    portfolio = read_portfolio(portfoliofile)
+    prices = read_prices(pricefile)
+
+    # Create the report data
+    report = make_report_data(portfolio, prices)
+
+    # Print it out
+    formatter = tableformat.create_formatter(fmt)
+    print_report(report, formatter)
+
+def main(args):
+    if len(args) != 4:
+        raise SystemExit('Usage: %s portfile pricefile format' % args[0])
+    portfolio_report(args[1], args[2], args[3])
+
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)

Solutions/7_4/stock.py

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+# stock.py
+
+class Stock(object):
+    '''
+    An instance of a stock holding consisting of name, shares, and price.
+    '''
+    __slots__ = ('name','_shares','price')
+    def __init__(self,name, shares, price):
+        self.name = name
+        self.shares = shares
+        self.price  = price
+
+    def __repr__(self):
+        return f'Stock({self.name!r}, {self.shares!r}, {self.price!r})'
+
+    @property
+    def shares(self):
+        return self._shares
+
+    @shares.setter
+    def shares(self, value):
+        if not isinstance(value,int):
+            raise TypeError("Must be integer")
+        self._shares = value
+
+    @property
+    def cost(self):
+        '''
+        Return the cost as shares*price
+        '''
+        return self.shares * self.price
+
+    def sell(self, nshares):
+        '''
+        Sell a number of shares and return the remaining number.
+        '''
+        self.shares -= nshares

Solutions/7_4/tableformat.py

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+# tableformat.py
+
+class TableFormatter(object):
+    def headings(self, headers):
+        '''
+        Emit the table headers
+        '''
+        raise NotImplementedError()
+
+    def row(self, rowdata):
+        '''
+        Emit a single row of table data
+        '''
+        raise NotImplementedError()
+
+class TextTableFormatter(TableFormatter):
+    '''
+    Output data in plain-text format.
+    '''
+    def headings(self, headers):
+        for h in headers:
+            print(f'{h:>10s}', end=' ')
+        print()
+        print(('-'*10 + ' ')*len(headers))
+
+    def row(self, rowdata):
+        for d in rowdata:
+            print(f'{d:>10s}', end=' ')
+        print()
+
+class CSVTableFormatter(TableFormatter):
+    '''
+    Output data in CSV format.
+    '''
+    def headings(self, headers):
+        print(','.join(headers))
+
+    def row(self, rowdata):
+        print(','.join(rowdata))
+
+class HTMLTableFormatter(TableFormatter):
+    '''
+    Output data in HTML format.
+    '''
+    def headings(self, headers):
+        print('<tr>', end='')
+        for h in headers:
+            print(f'<th>{h}</th>', end='')
+        print('</tr>')
+
+    def row(self, rowdata):
+        print('<tr>', end='')
+        for d in rowdata:
+            print(f'<td>{d}</td>', end='')
+        print('</tr>')
+
+class FormatError(Exception):
+    pass
+
+def create_formatter(name):
+    '''
+    Create an appropriate formatter given an output format name
+    '''
+    if name == 'txt':
+        return TextTableFormatter()
+    elif name == 'csv':
+        return CSVTableFormatter()
+    elif name == 'html':
+        return HTMLTableFormatter()
+    else:
+        raise FormatError(f'Unknown table format {name}')
+
+def print_table(objects, columns, formatter):
+    '''
+    Make a nicely formatted table from a list of objects and attribute names.
+    '''
+    formatter.headings(columns)
+    for obj in objects:
+        rowdata = [ str(getattr(obj, name)) for name in columns ]
+        formatter.row(rowdata)
+

Solutions/7_4/ticker.py

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+# ticker.py
+
+import csv
+import report
+import tableformat
+from follow import follow
+import time
+
+def select_columns(rows, indices):
+    for row in rows:
+        yield [row[index] for index in indices]
+
+def convert_types(rows, types):
+    for row in rows:
+        yield [func(val) for func, val in zip(types, row)]
+
+def make_dicts(rows, headers):
+    return (dict(zip(headers,row)) for row in rows)
+
+def parse_stock_data(lines):
+    rows = csv.reader(lines)
+    rows = select_columns(rows, [0, 1, 4])
+    rows = convert_types(rows, [str,float,float])
+    rows = make_dicts(rows, ['name','price','change'])
+    return rows
+
+def ticker(portfile, logfile, fmt):
+    portfolio = report.read_portfolio(portfile)
+    lines = follow(logfile)
+    rows = parse_stock_data(lines)
+    rows = (row for row in rows if row['name'] in portfolio)
+    formatter = tableformat.create_formatter(fmt)
+    formatter.headings(['Name','Price','Change'])
+    for row in rows:
+        formatter.row([ row['name'], f"{row['price']:0.2f}", f"{row['change']:0.2f}"] )
+
+def main(args):
+    if len(args) != 4:
+        raise SystemExit('Usage: %s portfoliofile logfile fmt' % args[0])
+    ticker(args[1], args[2], args[3])
+
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)