how to find its the last item in for loop ,when read from file - Python

Question

I want to read from the pList.csv file and write all item in a string, such that each row is separated by a comma.

the file has only one column. for example, the pList.csv is :

28469977

24446384

25968054

and output string must be: 28469977,24446384,25968054

for do this, have considered the following code. but there is a little problem

p_list = ""
with open("pList.csv", mode="r") as infile:
    reader = csv.reader(infile)
    for row in reader:
        p_list += row[0]
        if its_not_last_loop :
            p_list += ","

What expression is appropriate for its_not_last_loop so that , is not applied to the last row of the file?

You are looking for `str.join`. For example: `",".join(["hello", "world", "foo", "bar"])` returns `'hello,world,foo,bar'`. — Paul M., Jul 25 '20 at 18:13

score 0 · Accepted Answer · edited Jul 25 '20 at 19:23

0

Try this:

with open("pList.csv", mode="r") as infile:
    reader = csv.reader(infile)
    out_list = []
    for row in reader:
        out_list.append(row[0]) #row[0] get value for the sample input
    p_list = ",".join(out_list)
    print(p_list)

See What exactly does the .join() method do?

edited Jul 25 '20 at 19:23

Saam

75
8

answered Jul 25 '20 at 18:21

Kaushal Kumar

1,237
1
12
21

score 0 · Answer 2 · answered Jul 26 '20 at 02:32

0

This can be shortened to (and is faster)

with open("pList.csv", mode="r") as infile:
    reader = csv.reader(infile)
    p_list = ",".join(row[0] for row in reader)
    print(p_list)

answered Jul 26 '20 at 02:32

rioV8

24,506
3
32
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how to find its the last item in for loop ,when read from file - Python

2 Answers2