如何用python列表中的相应元素替换文件中每行的第一个单词？

Question

I have a file like this:

research_t 1:1 2:1 3:1 5:1 13:1 
computer_sc 14:1 19:1 21:1 23:1 25:1 26:1 29:1 36:1 44:1 49:1 50:1 51:1 52:1 57:1 68:1 70:1 71:1 75:1 79:1 
res_computer 1:1 2:1 3:1 5:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 15:1 16:1 17:1 18:1 20:1 21:1 22:1
fin_res 23:1 24:1 26:1 28:1 29:1 30:1 32:1 33:1 34:1 35:1 36:1 38:1 39:1 40:1 41:1 43:1 45:1 47:1 48:1 54:1 55:1 56:1 59:1 63:1 64:1 65:1 66:1 72:1 78:1 80:1 
computer_sc_field 2:1 37:1

I want to read the file line by line and check it like if the first word in the line has ' computer ' in it, then I want to replace the whole first word by 1 , else replace it by -1 .

I was doing something like this:

with open('file.txt', 'r') as f:
    wordlist = [line.split(None, 1)[0] for line in f]
    s = 'computer'
    for i in range(len(wordlist)):
        if s in wordlist[i]:
            wordlist[i] = str(1)
        else:
            wordlist[i] = str(-1)

Now, I get a list: [-1, 1, 1, -1, 1] . But how do I replace the first words of each line in the file with the corresponding element of this list?

Answer 1

You have to put the whole line together again, after replacing the first part:

with open('file.txt', 'r') as file_in:
    with open('output.txt', 'w') as file_out:
        for line in file_in:
            first, other = line.split(None,1)
            line = '%d %s' % (1 if 'computer' in first else -1, other)
            file_out.write(line)

Answer 2

content = open('file.txt').readlines()
with open('file.txt', 'w') as flux:
    for line in content:
        first_word = line.split()[0]
        new_word = 'computer' in first_word and '1' or '-1'
        flux.write(line.replace(first_word, new_word))

ps : answer involving the mode 'rw' is not compatible with python3

Answer 3

I would use the classical tempfile usage and process the file line by line :

tmpname = None
with open('file.txt', 'r') as fdin, tempfile.NamedTemporaryFile(
        prefix = 'temp_file', dir='.', delete=False) as fdout:
    tmpname = fdout.name
    for line in fdin:
        first_word, remain = line.split(None, 1)
        fdout.write('1' if 'computer' in first_word else '-1' + ' ' + remain)

os.remove('file.txt')
os.rename(tmpname, 'file.txt')

Answer 4

Through re module.

import re
with open('input.txt', 'r') as in_file:
    with open('output.txt', 'w') as out_file:
        for line in in_file:
            if line.startswith('computer'):
                line = re.sub(r'^\S+', r'1', line)
                out_file.write(line)
            else:
                line = re.sub(r'^\S+', r'-1', line)
                out_file.write(line)

Output:

-1 1:1 2:1 3:1 5:1 13:1 
1 14:1 19:1 21:1 23:1 25:1 26:1 29:1 36:1 44:1 49:1 50:1 51:1 52:1 57:1 68:1 70:1 71:1 75:1 79:1 
-1 1:1 2:1 3:1 5:1 7:1 8:1 9:1 10:1 11:1 12:1 13:1 15:1 16:1 17:1 18:1 20:1 21:1 22:1
-1 23:1 24:1 26:1 28:1 29:1 30:1 32:1 33:1 34:1 35:1 36:1 38:1 39:1 40:1 41:1 43:1 45:1 47:1 48:1 54:1 55:1 56:1 59:1 63:1 64:1 65:1 66:1 72:1 78:1 80:1 
1 2:1 37:1