ValueError:不能将字符串转换为浮点数。

I have:

我有:

data1=open('file1.txt','r')
data2=open('file2.txt','w+')

for line in data1.readlines():
    items = line.split(' ')
    x = log(float(items[0]))
    y = float(items[1])
    data2.write(x)
    data2.write('\t')
    data2.write(y)
    data2.write('\n')
data1=open('file1.txt','r')
dat