How to print line of a file after match an exact string pattern with python?

Question

I have a list

list = ['plutino?','res 2:11','Uranus L4','res 9:19','damocloid','cubewano?','plutino']

I want to search every element from the list in a file with the next format and print the line after match

1995QY9      |  1995_QY9     | plutino       |  32929  |                |    39.445  |   0.260  | 29.193    |    49.696   |    4.8   |     66  | #   0.400   |  1.21 BR-U   | ?
1997CU29     |  1997_CU29    | cubewano      |  33001  |                |    43.534  |   0.039  | 41.815    |    45.253   |    1.5   |    243  |             |  1.82 RR     | 
1998BU48     |  1998_BU48    | Centaur       |  33128  |                |    33.363  |   0.381  | 20.647    |    46.078   |   14.2   |    213  | #   0.052   |  1.59 RR     | ?
1998VG44     |  1998_VG44    | plutino       |  33340  |                |    39.170  |   0.250  | 29.367    |    48.974   |    3.0   |    398  | #   0.028   |  1.51 IR     | 
1998SN165    |  1998_SN165   | inner classic |  35671  |                |    37.742  |   0.041  | 36.189    |    39.295   |    4.6   |    393  | #   0.060   |  1.13 BB     | 
2000VU2      |  2000_VU2     | unusual       |  37117  | Narcissus      |     6.878  |   0.554  |  3.071    |    10.685   |   13.8   |     11  | #   0.088   |              | 
1999HX11     |  1999_HX11    | plutino?      |  38083  | Rhadamanthus   |    39.220  |   0.151  | 33.295    |    45.144   |   12.7   |    168  |             |  1.18 BR     | 
1999HB12     |  1999_HB12    | res 2:5       |  38084  |                |    56.376  |   0.422  | 32.566    |    80.187   |   13.1   |    176  |             |  1.39 BR-IR  |

I am using the next code to do that

for i in list:
with open("tnolist.txt") as f:
    for line in f:
        if re.search(i, line):
            print(line)

The code works fine for all element, except for plutino. When the variable i is plutino the code prints lines for plutino and for plutino?.

The ? in the string is making an issue. You need a mechanism to make an exact match for that string. You can do ind = i.index('?') ; i = i[:ind] + "\\" + i[ind:] to append \` in the string so that it will take ``? as an actual character in your search. — Sijan Bhandari
– Sijan Bhandari, Commented May 28, 2018 at 4:36
Do you actually re-open the file for each world in the list? — AGN Gazer
– AGN Gazer, Commented May 28, 2018 at 4:57
Finally, how can this code "work fine" when it does not "print the line after match"? — AGN Gazer
– AGN Gazer, Commented May 28, 2018 at 4:58

Hans Musgrave · Accepted Answer · 2018-05-28 04:31:34Z

2

This happens because plutino is a substring of plutino?, so the regex parser matches the first part of plutino? and returns a non-falsey answer. Without a whole lot of additional work, you should be able to fix the problem with re.search(i, line+r'\s'), which says that you need to have a whitespace character after the phrase you're searching. As the file gets longer and more complicated, you might have more such exceptions to make the regex behave as desired.

Update: I also like visual regex editors for reasons like this. They make it easy to see what matches and what doesn't.

Another option would be something like i==line.split('|')[2].strip() which extracts the portion of your file you seem to care about. The .strip() method can become inefficient on long lines, but this might fit your use case.

edited May 28, 2018 at 4:31

answered May 28, 2018 at 4:25

Hans Musgrave

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