dict () - Python 2.7 From 3.5 -

Question

Following my work on my prototype , I'm still trying to compare two CSV files. This time I use a dictionary.

My first file is something like:

IP
192.168.10.1
192.168.10.15
192.168.10.32

One single column, with IP addresses.

I want to check if these IP are also I another file called epoch.csv. If yes, I write a CSV file with the copy of the line in epoch.csv.

In Python 2.7, I wrote this code that works smoothly:

with open('IP.csv', 'r') as master:
    enum = csv.reader(master)
    master_indices = dict((r[0], i) for i, r in enumerate(enum))


with open('epoch.csv', 'r') as hosts:
    with open('result.csv', 'w') as results:
        reader = csv.reader(hosts)
        writer = csv.writer(results)

        for row in reader:
            index = master_indices.get(row[1])
            if index is not None:
                writer.writerow(row)

BUT, when I try to run this code with Python 3.5 (Windows), I get this error:

File "IP.py", line 43, in (module)
master_indices = dict((r[0], i) for i, r in enumerate(enum))
File "IP.py", line 43, in (genexpr)
master_indices = dict((r[0], i) for i, r in enumerate(enum))
IndexError: list index out of range

Why does it work in one case and not in the other one. I could of course reinstall 2.7 On all my machines, but I'd like to understand why it doesn't work...

EDIT :

So considering csv.DictReader, I guess I can modify this line :

with open('IP.csv', 'r') as master:
    enum = csv.reader(master)
    master_indices = dict((r[0], i) for i, r in enumerate(enum))

with something much simplier like this :

with open('IP.csv', 'r') as master:
    enum = csv.Dict.Reader(master)

Is it correct?

Answer 1

Is there any empty lines in IP.csv ?

Your code DID run "smoothly" in my computer under Python 3.5, but it will fail if I add a empty line to the start of the file.

Try to add print(enum) in your for loop and you will know what exactly lead to this exception.