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From: Ian Kelly <ian.g.kelly@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Howw to prevent the duplication of any value in a column within a CSV file (python)
Date: Tue, 26 Apr 2016 14:19:20 -0600
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On Tue, Apr 26, 2016 at 2:07 PM, Adam Davis <peakgraphicz@gmail.com> wrote:
> On Tuesday, 26 April 2016 20:52:54 UTC+1, Ian  wrote:
>> On Tue, Apr 26, 2016 at 1:05 PM, Joaquin Alzola
>> <Joaquin.Alzola@lebara.com> wrote:
>> > Just an example. Didn't use the csv but just hope that it helps.
>> >
>> > name=[]
>> > name_exist="Dop"
>> >
>> > with open("dop.csv") as f:
>> >         for line in f:
>> >                 line_split=line.split(',')
>> >                 name.append(line_strip[0])
>> >         if name_exist in name:
>> >                 print "found name " + name_exist + " Can not append"
>> >         else:
>> >                 file = open("dop.csv",'a')
>> >                 print "No name found"
>> >                 file.write(name_exist)
>> > file.close()
>>
>> Except that as noted elsewhere in the thread a set would be a better
>> choice than a list, since checking membership is much faster on a set.
>
> Thanks for your help Ian. I'm a beginner right now, could you instruct me as to how I would create a set?

Create a new set:

    my_set = set()

Add a value to the set:

    my_set.add(value)

Check for membership:

    value in my_set

See also the Python tutorial at
https://docs.python.org/3/tutorial/datastructures.html#sets