I have below data.csv

```
custId,contract,zone,teamcode,projectcode,time
2,2345,us_east,Red,A,5s
1,2345,us_west,Blue,B,1s
2,2346,eu_west,Yellow,C,2s
1,2345,us_west,Blue,D,1s
3,2346,eu_west,Yellow,E,2s

```

I don't want to use pandas here. 

I am new to python and I have no idea how to figure this out. I managed to read the data using csv but I don't know how to proceed next. 

```
import csv
with open('data.csv', 'r') as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

```

Edit: I need to find number of unique custId for each contract.