How to Print a string to a specific character? - string

Question

I have a file like this:
NA|polymerase|KC545393|Bundibugyo_ebolavirus|EboBund_112_2012|NA|2012|Human|Democratic_Republic_of_the_Congo
NA|VP24|KC545393|Bundibugyo_ebolavirus|EboBund_112_2012|NA|2012|Human|Democratic_Republic_of_the_Congo
NA|VP30|KC545393|Bundibugyo_ebolavirus|EboBund_112_2012|NA|2012|Human|Democratic_Republic_of_the_Congo
I am trying to print this characters from each line:
polymerase|KC545393
VP24|KC545393
VP30|KC545393
How can I do this?
I tried this code:
for character in line:
if character=="|":
print line[1:i.index(j)]

Answer 1

Use str.split() to split each line by the '|' character; you can limit the splitting because you only need the first 3 columns:
elems = line.split('|', 3)
print '|'.join(elems[1:3])
The print line then takes the elements at index 1 and 2 and joins them together again using the '|' character to produce your desired output.
Demo:
>>> lines = '''\
... NA|polymerase|KC545393|Bundibugyo_ebolavirus|EboBund_112_2012|NA|2012|Human|Democratic_Republic_of_the_Congo
... NA|VP24|KC545393|Bundibugyo_ebolavirus|EboBund_112_2012|NA|2012|Human|Democratic_Republic_of_the_Congo
... NA|VP30|KC545393|Bundibugyo_ebolavirus|EboBund_112_2012|NA|2012|Human|Democratic_Republic_of_the_Congo
... '''.splitlines(True)
>>> for line in lines:
... elems = line.split('|', 3)
... print '|'.join(elems[1:3])
...
polymerase|KC545393
VP24|KC545393
VP30|KC545393

Answer 2

Assuming you know that each line has at least two separators, you can use:
>>> s = 'this|is|a|string'
>>> s
'this|is|a|string'
>>> s[:s.find('|',s.find('|')+1)]
'this|is'
This finds the first | starting at the character position beyond the first | (i.e., it finds the second |) then gives you the substring up but not including to that point.
If it may not have two separators, you just have to be more careful:
s = 'blah blah'
result = s
if s.find('|') >= 0:
if s.find('|',s.find('|')+1) >= 0:
result = s[:s.find('|',s.find('|')+1)]
If that's the case, you'll probably definitely want it in a more general purpose function, something like:
def substringUpToNthChar(str,n,ch):
if n < 1: return ""
pos = -1
while n > 0:
pos = str.find(ch,pos+1)
if pos < 0: return str
n -= 1
return str[:pos]
This will correctly handle the case where there's fewer separators than desired and will also handle (relatively elegantly) getting more than the first two fields.