打印出以两个不同的字符串输出开头的行？

Question

I am trying to scan an input file and print out parts of lines that begin with a certain string. The text file is 10000+ lines, but I am only concerned with the beginning line, and more specifically the data within that line. For clarification, here are two lines of code which explain what I am trying to say.

inst "N69" "IOB",placed BIOB_X11Y0 R8  ,

inst "n0975" "SLICEX",placed CLEXL_X20Y5 SLICE_X32Y5  ,

Here is the code that I have gotten to so far:

searchfile = open("C:\PATH\TO\FILE.txt","r")
for line in searchfile:
    if "inst " in line: 
        print line
searchfile.close()

Now this is great if I am looking for all lines that start with "inst", but I am specifically looking for lines that start with "inst "N"" or "inst "n"". From there, I wanted to extract just the string starting with N or n.

My idea was to first extract those lines (as shown above) to a new .txt file, then run another script to get only the portions of the lines that have N or n. In the example above, I am only concerned with N69 and n0975. Is there an easier method of doing this?

Answer 1

With re.search() function:

Sample file.txt content:

inst "N69" "IOB",placed BIOB_X11Y0 R8  ,
some text
inst "n0975" "SLICEX",placed CLEXL_X20Y5 SLICE_X32Y5  ,
text
another text

---

import re

with open('file.txt', 'r') as f:
    for l in f.read().splitlines():
        m = re.search(r'^inst "([Nn][^"]+)"', l)
        if m:
            print(m.group(1))

The output:

N69
n0975

Answer 2

Yes with the re module.

re.finditer(r'^inst\s+\"n(\d+)\"', the_whole_file, re.I)

Will return you an iterator of all the matches. For each match you will need to do .group(1) to get those numbers you wanted.

Notice that you don't need to filter the file first using this method. You can do this for the whole file.

The output in your case will be:

69
0975

Answer 3

Here is one solution:

with open('nfile.txt','r') as f:
    for line in f:
        if line.startswith('inst "n') or line.startswith('inst "N'):
            print line.split()[1]

For each line in the file startswith part checks if the line starts with one of your target patters. If yes, it splits the line using split and prints the second component which is the part with n or N .