Pandas Lambda Function with Nan Support

Question

I am trying to write a lambda function in Pandas that checks to see if Col1 is a Nan and if so, uses another column\'s data. I have having trouble getting code (below) to c

Answer 1

Within pandas 0.24.2, I use

df.apply(lambda x: x['col_name'] if x[col1] is np.nan else expressions_another, axis=1)

because pd.isnull() doesn't work.

in my work,I found the following phenomenon,

No running results:

df['prop'] = df.apply(lambda x: (x['buynumpday'] / x['cnumpday']) if pd.isnull(x['cnumpday']) else np.nan, axis=1)

Results exist:

df['prop'] = df.apply(lambda x: (x['buynumpday'] / x['cnumpday']) if x['cnumpday'] is not np.nan else np.nan, axis=1)