只读文本文件python中指定行中的数字

我试着从一个文本文件的第18行和第19行中读取两个浮点数并求出它们的平均值。请只看由 ######### 是的。

这个文件是单词和数字的混合体,我不知道怎么读这些数字。第18行和第19行的示例如下:

TM-score= 0.27878 (if normalized by length of Chain_1)
TM-score= 0.36068 (if normalized by length of Chain_2)

def tmval(self,name,tmvalpath):
    dir = tmvalpath
    splits = []
    avg = 0
    number1 = 0
    number2 = 0
    for f in os.listdir(dir):
        file_name2, file_ext = os.path.splitext(f)
        n1,n2,align = file_name2.split('_')
        n = ('{}_{}'.format(n1,n2))
        if n == name:
#####################################################
            with open(os.path.join(dir,f)) as file:
                for i, line in enumerate(file):
                    if i == 17:
                       #retrieve data from 18th line
                       number1 =
                    elif i == 18:
                       # retrieve data from 19th line
                       number2 = 
######################################################
  avg = float(number1 + number2)/2                      
  return avg