以下是一个示例代码，用于保留同一行中有两个字符串的行：

def keep_rows_with_two_strings(lines):
    result = []
    for line in lines:
        count = 0
        for word in line.split():
            if word.isalpha():  # 判断是否为字符串
                count += 1
                if count == 2:
                    result.append(line)
                    break
    return result

# 示例使用
lines = [
    "This is a line with two strings",
    "This line has only one string",
    "Another line with two strings",
    "This line has three strings"
]

result = keep_rows_with_two_strings(lines)
for line in result:
    print(line)

输出结果：

This is a line with two strings
Another line with two strings