Iterating In Dataframe And Writing Down The Index Of The Values Where A Condition Is Met

I have a data made of 20 rows and 2500 columns. Each column is a unique product and rows are time series, results of measurements. Therefore each product is measured 20 times and t

Solution 1:

Simply use .gt + .idxmax, which will give you the index of the first time your condition is met.

import pandas as pd
import numpy as np

np.random.seed(12)
df = pd.DataFrame(np.random.randint(1,5,(20,2500)))

df.gt(3).idxmax()
#0        0
#1        0
#2        4
#3        4
#4        1
#...
#2496     8
#2497     0
#2498     5
#2499     1