Question

我正在编写一个脚本，我需要将CSV读入<div> <p>Away from keyboard?</p> <ul class="button"> <li><a href="#0">I'm Back!</a></li> </ul> </div>，对字段执行一些操作（数据重叠），然后通过{{1}将DictReader输出到csv }。

如果我读了CSV然后写了Dict，那么这个过程就可以了。

DictReader

然而 - 如果我添加一个新列，似乎我丢失了DictReader中的所有数据：

DictWriter

在我写这篇文章之前，有没有办法在DictReader上执行工作？

Answer 1

由于csvread已被第一个for循环完全占用，我们的with语句将输出一个空白文件，您可能会注意到。

你应该：

- ＆GT;将行保存到变量

import csv
headers = ['Symbol', 'Price', 'Date', 'Time', 'Change', 'Volume']
rows = [{'Symbol':'AA', 'Price':39.48, 'Date':'6/11/2007',
         'Time':'9:36am', 'Change':-0.18, 'Volume':181800},
        {'Symbol':'AIG', 'Price': 71.38, 'Date':'6/11/2007',
         'Time':'9:36am', 'Change':-0.15, 'Volume': 195500},
        {'Symbol':'AXP', 'Price': 62.58, 'Date':'6/11/2007',
         'Time':'9:36am', 'Change':-0.46, 'Volume': 935000}]

with open('stocks.csv','w') as f:
    f_csv = csv.DictWriter(f, headers)
    f_csv.writeheader()
    f_csv.writerows(rows)

with open('stocks.csv', 'r') as file:
    csvread = csv.DictReader(file, delimiter=',')

    rows = []
    for row in csvread:
        row['NewColumn'] = '1'
        rows.append(row)

    with open('out.csv', 'w') as out:
        headertowrite = ['Time', 'Symbol', 'NewColumn']
        writer = csv.DictWriter(out, headertowrite, extrasaction='ignore')
        writer.writeheader()
        writer.writerows(rows)

或

- ＆GT;在将输出文件的with语句中进行修改（您读取一行，修改并写入。

import csv
headers = ['Symbol', 'Price', 'Date', 'Time', 'Change', 'Volume']
rows = [{'Symbol':'AA', 'Price':39.48, 'Date':'6/11/2007',
         'Time':'9:36am', 'Change':-0.18, 'Volume':181800},
        {'Symbol':'AIG', 'Price': 71.38, 'Date':'6/11/2007',
         'Time':'9:36am', 'Change':-0.15, 'Volume': 195500},
        {'Symbol':'AXP', 'Price': 62.58, 'Date':'6/11/2007',
         'Time':'9:36am', 'Change':-0.46, 'Volume': 935000}]

with open('stocks.csv','w') as f:
    f_csv = csv.DictWriter(f, headers)
    f_csv.writeheader()
    f_csv.writerows(rows)

with open('stocks.csv', 'r') as file:
    csvread = csv.DictReader(file, delimiter=',')

    with open('out.csv', 'w') as out:
        headertowrite = ['Time', 'Symbol', 'NewColumn']
        writer = csv.DictWriter(out, headertowrite, extrasaction='ignore')
        writer.writeheader()
        for row in csvread:
            row['NewColumn'] = '1'
            writer.writerow(row)

小心！在第二个解决方案中，writerow不是writerows！

请注意，我还强烈推荐第二种解决方案，它在内存消耗方面具有更高的可扩展性。

csv DictReader上的“做功”失败了

1 个答案: