How to Filter specific values against specific words from text file and store it in list?

Question

Like i have a text file abc.txt and it is like this

we 2 rt 3 re 3 tr vh kn mo
we 3 rt 5 re 5 tr yh kn me
we 4 rt 6 re 33 tr ph kn m3
we 5 rt 9 re 34 tr oh kn me
we 6 rt 8 re 32 tr kh kn md

now i want the values against the tr and after filtering it should get this result

[vh,yh,ph,oh,kh]

can anyone tell how to do it.what code should be write for it

Answer 1

mylist = [line.split()[7] for line in myfile] 

should work if it's always the 8th column.

If the position of tr is variable, you could do

mylist = []
for line in myfile:
    items = line.split()
    mylist.append(items[items.index("tr")+1])

Answer 2

You can split the lines as before tr and after tr and obtain the first word in the second part.

[ line.split(' tr ')[1].split()[0] for line in file ] 

If there is more than one tr , the expression collects the word after the first one. Alternatively, this one collects the words after the last tr in a line:

[ line.split(' tr ')[-1].split()[0] for line in file ]

Answer 3

Your question is not quite clear. Does this what you are after?

[line.split()[7] for line in open("abc.txt")]

It returns the eighth "word" from every line.

Answer 4

If I understand correctly, something like this should do the job (not tested):

resultArray = []
for aString in yourFile:
    anArray = aString.split()
    for i in range(0, len(anArray) - 1):  //-1 in case tr is at the end of array
        if anArray[i] == 'tr':
            resultArray.append(anArray[i + 1])

Answer 5

from operator import itemgetter

# tr value is in the 8th column
tr = itemgetter(7)

print map(tr, (line.split() for line in myfile.readlines()))

Answer 6

One may try the following:

def filter_words(filename, magic_word):
    with open(filename) as f:
        all_words = f.read().strip().split()
        filtered_words = []
        i = 0
        while True:
            try:
                i = all_words.index(magic_word, i) + 1
                filtered_words.append(all_words[i])
            except IndexError, ValueError:
                break
        return filtered_words

This algorithm does not fail in case 'tr' happens to be the last word in the provided text file.

Example:

>>> filter_words('abc.txt', 'tr')
['vh', 'yh', 'ph', 'oh', 'kh']

Answer 7

Wouldn't be simpler to use a regex ?

If 'we' , 'rt' , 're' , 'tr' are really constant at their places :

import re

ch = '''
we 2 rt 3 re 3 tr vh kn mo
we 3 rt 5 re 5 tr yh kn me
we 4 rt 6 re 33 tr ph kn m3
we 5 rt 9 re 34 tr oh kn me
we 6 rt 8 re 32 tr kh kn md'''

print re.findall('(?<= tr )([^ ]+)',ch)

If not, and then the position being the criterium to determine what to catch:

import re

ch = '''
we 2 rt 3 re 3 tr vh kn mo
we 3 rt 5 re 5 tr yh kn me
we 4 rt 6 re 33 tr ph kn m3
we 5 rt 9 re 34 tr oh kn me
we 6 rt 8 re 32 tr kh kn md'''

print [ mat.group(1)
        for mat in re.finditer('^(?:\w+ \d+ ){3}\w+ ([^ ]+) .+',ch,re.M)]