python-mastery/Exercises/soln5_1.md

Exercise 5.1 - Solution

This is a partial solution that does not include type-hints.

# reader.py

import csv

def csv_as_dicts(lines, types, *, headers=None):
    '''
    Convert lines of CSV data into a list of dictionaries
    '''
    records = []
    rows = csv.reader(lines)
    if headers is None:
        headers = next(rows)
    for row in rows:
        record = { name: func(val)
                   for name, func, val in zip(headers, types, row) }
        records.append(record)
    return records

def csv_as_instances(lines, cls, *, headers=None):
    '''
    Convert lines of CSV data into a list of instances
    '''
    records = []
    rows = csv.reader(lines)
    if headers is None:
        headers = next(rows)
    for row in rows:
        record = cls.from_row(row)
        records.append(record)
    return records

def read_csv_as_dicts(filename, types, *, headers=None):
    '''
    Read CSV data into a list of dictionaries with optional type conversion
    '''
    with open(filename) as file:
        return csv_as_dicts(file, types, headers=headers)

def read_csv_as_instances(filename, cls, *, headers=None):
    '''
    Read CSV data into a list of instances
    '''
    with open(filename) as file:
        return csv_as_instances(file, cls, headers=headers)

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