python - Row count in a csv file

Question

I am probably making a stupid mistake, but I can't find where it is. I want to count the number of lines in my csv file. I wrote this, and obviously isn't working: I have row_count = 0 while it should be 400. Cheers.

f = open(adresse,"r")
reader = csv.reader(f,delimiter = ",")
data = [l for l in reader]
row_count = sum(1 for row in reader)

print row_count

Answer 1

with open(adresse,"r") as f:
    reader = csv.reader(f,delimiter = ",")
    data = list(reader)
    row_count = len(data)

You are trying to read the file twice, when the file pointer has already reached the end of file after saving the data list.