Effective way to get part of string until token
Question: I'm parsing a very big csv (big = tens of gigabytes) file in python and I need
only the value of the first column of every line. I wrote this code, wondering
if there is a better way to do it:

    
    
    delimiter = ','
    f = open('big.csv','r')
    for line in f:
        pos = line.find(delimiter)
        id = int(line[0:pos])
    

Is there a more effective way to get the part of the string before the first
delimiter?

**Edit:** I do know about the CSV module (and I have used it occasionally),
but I do not need to load in memory every line of this file - I need the first
column. So lets focus on string parsing.


Answer: 
    >>> a = '123456'
    >>> print a.split('2', 1)[0]
    1
    >>> print a.split('4', 1)[0]
    123
    >>> 
    

But, if you're dealing with a CSV file, then:

    
    
    import csv
    with open('some.csv') as fin:
        for row in csv.reader(fin):
            print int(row[0])
    

And the csv module will handle quoted columns containing quotes etc...

