I have the following DF:
I want to remove all rows whereby TO and GP columns are negative and '0', and remove all rows whereby TTS and BMI columns are positive and '0'.
I have tried creating code like the following for each column however this is also deleting rows that are null which I do not want:
df [df ['GP'] >= 0]
What's the most efficient way to do this?

df[(df['GP'] >= 0) & (df['GP'] != np.NaN)]and get round the difficulty of & - its caught me out many a time