How to read specific lines of a large csv file

Question

I am trying to read some specific rows of a large csv file, and I don\'t want to load the whole file into memory. The index of the specific rows are given in a list L

Answer 1

Assuming L is a list containing the line numbers you want, you could do :

with open("~/file.csv") as f:
    r = csv.DictReader(f)
    for i, line in enumerate(r):
        if i in L:    # or (i+2) in L: from your second example
            print line

That way :

• you read the file only once
• you do not load the whole file in memory
• you only get the lines you are interested in

The only caveat is that you read whole file even if L = [3]