Merge pull request #2 from altvec/chapter2-3

altvec · web-flow · commit e81ffc9ed139 · 2020-06-28T19:33:52.000+05:00
Complete chapter 2 and 3 exercises
diff --git a/Work/fileparse.py b/Work/fileparse.py
@@ -1,3 +1,46 @@
 # fileparse.py
 #
 # Exercise 3.3
+
+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.
+    '''
+    if select and not has_headers:
+        raise RuntimeError("Select argument requires column headers")
+
+    rows = csv.reader(lines, delimiter=delimiter)
+    headers = next(rows) if has_headers else []
+    if select:
+        indices = [headers.index(colname) for colname in select]
+        headers = select
+    records = []
+    for idx, row in enumerate(rows, start=1):
+        if not row:
+            continue
+        if select:
+            row = [row[index] for index in indices]
+        if types:
+            try:
+                row = [func(val) for func, val in zip(types, row)]
+            except ValueError as e:
+                if not silence_errors:
+                    print(f'Row {idx}: Couldn\'t convert {row}')
+                    print(f'Row {idx}: Reason {e}')
+                continue
+        if headers:
+            record = dict(zip(headers, row))
+        else:
+            record = tuple(row)
+        records.append(record)
+    return records
diff --git a/Work/pcost.py b/Work/pcost.py
@@ -1,30 +1,24 @@
+#!/usr/bin/env python3
+
 # pcost.py
 #
 # Exercise 1.27
-import sys
-import csv
+from report import read_portfolio
 
 
 def portfolio_cost(filename):
     '''Return portfolio cost.'''
-    cost = 0.0
-    with open(filename, 'rt') as file:
-        rows = csv.reader(file)
-        next(rows)  # skip headers
-        for row in rows:
-            _, shares, price = row
-            try:
-                cost += int(shares) * float(price)
-            except ValueError as err:
-                print(err)
-                continue
-    return cost
+    portfolio = read_portfolio(filename)
+    return sum([s['shares'] * s['price'] for s in portfolio])
+
 
+def main(args):
+    if len(args) != 2:
+        raise SystemExit(f'Usage: {args[0]} portfolio_file')
+    cost = portfolio_cost(args[1])
+    print(f'Total cost: {cost}')
 
-if len(sys.argv) == 2:
-    filename = sys.argv[1]
-else:
-    filename = '../Work/Data/portfolio.csv'
 
-cost = portfolio_cost(filename)
-print(f'Total cost: {cost}')
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)
diff --git a/Work/report.py b/Work/report.py
@@ -1,3 +1,69 @@
+#!/usr/bin/env python3
+
 # report.py
 #
 # Exercise 2.4
+from fileparse import parse_csv
+
+
+def read_portfolio(filename):
+    '''
+    Read a stock portfolio file into a list of dictionaries with keys
+    name, shares, and price.
+    '''
+    with open(filename) as lines:
+        return parse_csv(
+            lines,
+            select=['name', 'shares', 'price'],
+            types=[str, int, float],
+        )
+
+
+def read_prices(filename):
+    '''
+    Read a CSV file of price data into a dict mapping names to prices.
+    '''
+    with open(filename) as lines:
+        return dict(parse_csv(lines, types=[str, float], has_headers=False))
+
+
+def make_report(portfolio, prices):
+    report = []
+    for s in portfolio:
+        current_price = prices[s['name']]
+        change        = current_price - s['price']
+        report.append(
+            (s['name'], s['shares'], current_price, change)
+        )
+    return report
+
+
+def print_report(report):
+    '''
+    Print formatted report.
+    '''
+    headers = ('Name', 'Shares', 'Price', 'Change')
+    print('%10s %10s %10s %10s' % headers)
+    print(('-' * 10 + ' ') * len(headers))
+    for row in report:
+        print('%10s %10d %10.2f %10.2f' % row)
+
+
+def portfolio_report(portfolio_file, prices_file):
+    '''
+    Make a stock report given portfolio and price data files.
+    '''
+    portfolio = read_portfolio(portfolio_file)
+    prices    = read_prices(prices_file)
+    report    = make_report(portfolio, prices)
+    print_report(report)
+
+
+def main(args):
+    if len(args) != 3:
+        raise SystemExit(f'Usage: {args[0]} portfolio_file prices_file')
+    portfolio_report(args[1], args[2])
+
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)
