coding-mentor-agent/kb/python-course-kb-practical-python/wiki/exercises/3-3-reading-csv-files.md

id, source_exercise_id, title, section, source_path, source_repo, source_commit, student_visible_solution, has_private_solution, skip

id	source_exercise_id	title	section	source_path	source_repo	source_commit	student_visible_solution	has_private_solution	skip
practical-python-3.3	3.3	Reading CSV Files	3.2 More on Functions	03_Program_organization/02_More_functions.md	https://github.com/dabeaz-course/practical-python	93dca856b41c61a0a0f85ae334116e4c125629ea	false	false	false

Exercise 3.3: Reading CSV Files

Source: Practical Python Programming, 03_Program_organization/02_More_functions.md.

Exercise 3.3: Reading CSV Files

To start, let’s just focus on the problem of reading a CSV file into a list of dictionaries. In the file fileparse.py, define a function that looks like this:

# fileparse.py
import csv

def parse_csv(filename):
    '''
    Parse a CSV file into a list of records
    '''
    with open(filename) as f:
        rows = csv.reader(f)

        # Read the file headers
        headers = next(rows)
        records = []
        for row in rows:
            if not row:    # Skip rows with no data
                continue
            record = dict(zip(headers, row))
            records.append(record)

    return records

This function reads a CSV file into a list of dictionaries while hiding the details of opening the file, wrapping it with the csv module, ignoring blank lines, and so forth.

Try it out:

Hint: python3 -i fileparse.py.

>>> portfolio = parse_csv('Data/portfolio.csv')
>>> portfolio
[{'price': '32.20', 'name': 'AA', 'shares': '100'}, {'price': '91.10', 'name': 'IBM', 'shares': '50'}, {'price': '83.44', 'name': 'CAT', 'shares': '150'}, {'price': '51.23', 'name': 'MSFT', 'shares': '200'}, {'price': '40.37', 'name': 'GE', 'shares': '95'}, {'price': '65.10', 'name': 'MSFT', 'shares': '50'}, {'price': '70.44', 'name': 'IBM', 'shares': '100'}]
>>>

This is good except that you can’t do any kind of useful calculation with the data because everything is represented as a string. We’ll fix this shortly, but let’s keep building on it.

关联来源

• summaries/02_More_functions