在Python中以这种方式打开的CSV文件的文件句柄

如何解决在Python中以这种方式打开的CSV文件的文件句柄

我具有以下代码来打开和读取csv文件。

#!/usr/bin/env python3
import csv

## Overriding csv.DictReader to strip whitespace and ignore case
class MyDictReader(csv.DictReader,object):
    @property
    def fieldnames(self):
        return [field.strip().lower() for field in super(MyDictReader,self).fieldnames]

# Read csv file
def csv_dict_reader(infile):
    reader = MyDictReader(open(infile),delimiter=',',skipinitialspace=True)
    return reader

def main():
    csvfile = 'mycsvfile.csv'
    dict_reader = csv_dict_reader(csvfile)

    for row_line in dict_reader:
        print(row_line)

if __name__ == '__main__':
    main()

为了完整起见，我也添加了csvfile：

sl,applicationid,firstname,lastname
1,Y20QWERT,User1,Name1
2,Y20ZXCVB,User2,Name2
3,Y20WMXK,User3,Name3

如果要关闭并再次重新打开，csvfile的文件句柄是什么？