Pandas - 检查系列中的所有值是否都是 NaN

Question

I have a data series which looks like this:

print mys

id_L1
2       NaN
3       NaN
4       NaN
5       NaN
6       NaN
7       NaN
8       NaN

I would like to check is all the values are NaN.

My attempt:

pd.isnull(mys).all()

Output:

True

Is this the correct way to do it?

Answer 1

是的，这是正确的，但我认为更惯用的方式是：

mys.isnull().all()

Answer 2

这将检查所有列..

mys.isnull().values.all(axis=0)

Answer 3

if df['col'].count() > 0:
    then ...

This works well but I think it might be quite a slow approach. I made the mistake of embedding this into a 6000-times loop to test four columns - and it's brutal, but I can blame the programmer clearly :)

Obviously, don't be like me. Always: Test your columns for all-null once, set a variable with the yes - "empty" or no - "not empty" result - and then loop.