python如何删掉txt指定字符后面的内容

#删除指定符号后的内容
import re
list = []
matchPattern = re.compile(r'%')#指定符号
file = open('D:/11.txt','r', encoding='gb18030')#路径  
while 1:
    line = file.readline()
    p1,p2,p3=line.partition('%')#指定符号
    if not line:
        break
    elif matchPattern.search(line):
        list.append(p1)
        list.append('n')
    else:
        list.append(line)
file.close()
file = open('D:/11.txt', 'w')
for i in list:
    file.write(i)
file.close()