In a pandas dataframe I have a field 'amp' that should be populated by a list of length 495. Is there a panda-ic way to quickly filter on this length, such that all rows with field 'amp' are not equal to 495 are dropped?
df[len(df['amp']) == 495]
If you specifically need
len, then @MaxU's answer is best.
For a more general solution, you can use the map method of a Series.
df[df['amp'].map(len) != 495]
This will apply
len to each element, which is what you want. With this method, you can use any arbitrary function, not just