无法写入文件（Python）

Question

我想基于另一个文件中的关键字列表来提取XML文件的某些节点；如果关键字存在于指示节点中，则该节点的文本以及其他某些节点的文本应写入CVS文件中。 有人可以告诉我为什么我的代码不起作用吗？尽管我确信关键字在指示节点中存在，但是只有头部写入了输出文件！

import xml.etree.ElementTree as ET
from xml.etree.ElementTree import tostring
import csv

tree=ET.parse('/Users/m/dru.xml')
tree = tree.getroot()
t = tostring(tree)
t = t.lower()
tree= ET.fromstring(t)

dru = open('/Us/druall.csv', 'a')
csvwriter = csv.writer(dru)

dru_head = []
count = 0
keywords=open('/Users/m/test.txt', 'r')

for channel in tree.findall('.//drug'):
    if count == 0:
        Indication_header = channel.find('./indication').tag
        dru_head.append(Indication_header)
        Name_header = channel.find('name').tag
        dru_head.append(Name_header)
        [x.encode('utf-8') for x in dru_head]
        csvwriter.writerow(dru_head)
        count = count + 1

    if channel.find('./indication') is not None:
        comment = channel.find('./indication')
        if comment.text is not None:
            for x in keywords:
                x.strip().strip("").lower()
                dru_info = []
                if x in comment.text:
                        dru_info.append(channel.find('indication').text)
                        if channel.find('name') is not None:
                            dru_info.append(channel.find('name').text)
                        else:
                            print("Name: No data")
                else:
                        print("   ");
                csvwriter.writerow(dru_info)

drugB.close()

感谢您的帮助！