Python 在特定字符串之前插入文本

import re
result = []
with open("/Users/ec/Desktop/api.txt", "r+") as f:#路径
    a = [x.rstrip() for x in f]
    for item in a:
        if item.startswith("EC"):#EC开头的行前插入字符串
            break
    ind = a.index(item)
    result.extend(a[:ind])
    f.write('Hello Everyone')#写入字符串