# Replace all empty lists ([], '[]') in dataframe with NaN's
df = df.mask(df.applymap(str).eq('[]'))

# Replace all zeros in dataframe with NaN's
df[df == 0.0] = np.nan

# Replace empty strings in dataframe with NaN's
df.replace('', np.nan, inplace=True)

# Replace all strings with value 'null' in a dataframe with NaN
df.replace('null', np.NaN, inplace=True)

mask = df.applymap(str).isin(["[]", 0.0, "", "null"])
df = df.where(~mask, other=np.nan)