manipulate file and join by two different character symbols

Question

consider the tab-separated file foo.txt:

chrY    1208806 1208908 +   .
chrY    1212556 1212620 +   .
chrY    1465479 1466558 +   .

The goal is to manipulate foo.txt to obtain result.txt as such:

chrY:1208806-1208908
chrY:1212556-1212620
chrY:1465479-1466558

What I can achieve is only joining by one specific separator not two different ones --> my code:

with open(filename,'r') as f:
    for line in f:
        l = line.split()[0:3]
        result = ':'.join(l)
        print(result)

My outcome:

chrY:1208806:1208908
chrY:1212556:1212620
chrY:1465479:1466558

score 1 · Accepted Answer · answered Apr 29 '21 at 06:58

1

This works

with open(filename,'r') as f:
    for line in f:
        l = line.split()[0:3]
        result = f'{l[0]}:{l[1]}-{l[2]}'
        print(result)

answered Apr 29 '21 at 06:58

the__hat_guy

score 1 · Answer 2 · answered Apr 29 '21 at 06:59

1

Here is a solution you can try out,

with open(file_name, "r") as f:
    for l in f.readlines():
        print("{0}:{1}-{2}".format(*l.split()[:3]))

chrY:1208806-1208908
chrY:1212556-1212620
chrY:1465479-1466558

answered Apr 29 '21 at 06:59

sushanth

what is `*` doing in `*l.split()[:3])` ? expanding ? – moth Apr 29 '21 at 07:05
yes `*` is for unpacking, https://stackoverflow.com/a/3480190/4985099 – sushanth Apr 29 '21 at 07:39
why using `readlines` ? for a large file it gets slow. nice for the unpacking though. – moth Apr 30 '21 at 05:55

2 Answers2