python matplotlib 画两条折线图 其中一组数据有空值 如何处理？

python matplotlib 画两条折线图 其中一组数据有空值 如何处理？

import csv
from datetime import datetime
from matplotlib import pyplot as plt

filename = 'data.csv'
with open(filename) as f:
reader = csv.reader(f)
header_row = next(reader)

dates = []
temp1 = []
temp2 = []

for row in reader:
    time = row[1] + '-' + row[2] + '-' + row[3]
    current_date = datetime.strptime(time, "%Y-%m-%d")
    dates.append(current_date)

    tempm1 = int(float(row[7]))
    temp1.append(tempm1)

    tempm2 = int(row[28])
    temp2.append(tempm2)

fig = plt.figure(dpi=128, figsize=(10,6))
plt.plot(dates, temp1, c='red')
plt.plot(dates, temp2, c='blue')

plt.show()

报错：
C:\Users\yo\AppData\Local\Programs\Python\Python37\python.exe F:/论文/data/compare/compare.py
Traceback (most recent call last):
File "F:/论文/data/compare/compare.py", line 26, in
tempm2 = int(row[28])
ValueError: invalid literal for int() with base 10: '20.075'

Process finished with exit code 1

试过if 不为空值处理，然后数据对不齐了
我想要如果是空值图上就不显示
数据是有小数的所以就用int float 处理
请各位大神帮忙 谢谢！

https://blog.csdn.net/xiami_tao/article/details/79167273