python - Difference between maximum and second maximum from a DataFrame -

i have dataframe wanted difference between maximum , second maximum dataframe new column appended dataframe output.

the data frame looks example (this quite huge dataframe):

 gene_id    time_1  time_2  time_3   0.01489251  8.00246 8.164309 b   6.67943235  0.8832114   1.048761 

so far tried following it's taking headers,

largest = max(df) second_largest = max(item item in df if item < largest) 

and returning header value alone.

you can define func takes values, sorts them, slices top 2 values ([:2]) calculates difference , returns second value (as first value nan). apply , pass arg axis=1 apply row-wise:

in [195]: def func(x):     return -x.sort(inplace=false, ascending=false)[:2].diff()[1]  df['diff'] = df.loc[:,'time_1':].apply(func, axis=1) df  out[195]:   gene_id    time_1    time_2    time_3      diff 0        0.014893  8.002460  8.164309  0.161849 1       b  6.679432  0.883211  1.048761  5.630671