这个功能应该很接近你想要的.我已经在 Python 2.7.9 和 3.4.2 中对其进行了测试.我发布的初始版本有一些问题，因为 —正如我所提到的—它未经测试.我不确定您使用的是 Python 2 还是 Python 3，但这在任何一个中都可以正常工作.

This function should be very close to what you want. I've tested it in both Python 2.7.9 and 3.4.2. The initial version I posted had some problems because — as I mention then — it was untested. I'm not sure if you're using Python 2 or 3, but this worked properly in either one.

与之前版本相比的另一个变化是可选关键字日期参数的名称已从 cutoff_date 更改为 start_date 以更好地反映它的内容.截止日期通常表示可以执行的最后日期某事——与您在问题中使用它的方式相反.另请注意，提供的任何日期都应为字符串，即 start_date='20140401'，而不是整数.

Another change from the previous version is that the optional keyword date argument's name had been changed from cutoff_date to start_date to better reflect what it is. A cutoff date usually means the last date on which it is possible to do something—the opposite of the way you used it in your question. Also note that any date provided should a string, i.e. start_date='20140401', not as an integer.

一项增强功能是，如果指定了但不存在，它现在将创建输出目录.

One enhancement is that it will now create the output directory if one is specified but doesn't already exist.

import csv
import os
import sys

def open_csv(filename, mode='r'):
    """ Open a csv file in proper mode depending on Python verion. """
    return (open(filename, mode=mode+'b') if sys.version_info[0] == 2 else
            open(filename, mode=mode, newline=''))

def process_file(filename, start_date=None, new_dir=None):
    # Read the entire contents of the file into memory skipping rows before
    # any start_date given (assuming row[0] is a date column).
    with open_csv(filename, 'r') as f:
        reader = csv.reader(f)
        header = next(reader)  # Save first row.
        contents = [row for row in reader if start_date and row[0] >= start_date
                                                or not start_date]

    # Create different output file path if new_dir was specified.
    basename = os.path.basename(filename)  # Remove dir name from filename.
    output_filename = os.path.join(new_dir, basename) if new_dir else filename
    if new_dir and not os.path.isdir(new_dir):  # Create directory if necessary.
        os.makedirs(new_dir)

    # Open the output file and create a CSV writer for it.
    with open_csv(output_filename, 'w') as f:
        writer = csv.writer(f)

        # Add name of new column to header.
        header = ['Pipe'] + header  # Prepend new column name.
        writer.writerow(header)

        # Data for new column is the base filename without extension.
        new_column = [os.path.splitext( os.path.split(basename)[1] )[0]]

        # Process each row of the body by prepending data for new column to it.
        writer.writerows((new_column+row for row in contents))