如何使用Python替换文件中的大部分文本？

Question

I am required to use Python 2.3, and I have almost no programming experience.

I have a large number of files that look exactly like the one below. I want to replace the lines following the "0 2" with other ones which look basically the same but have different numbers.

Any suggestions? Thanks for the help!

%chk=Li-000+NT-4-SP-B3LYP-6-31+Gx_chk.chk
# ub3lyp/6-31+G* scf=xqc geom=connectivity

Li-000+NT-4-SP-B3LYP-6-31+Gx_chk

0 2
 C              
 C                  1    2.23392993
 C                  2    2.23392993    1   90.00000000
 C                  3    2.23392993    2   90.00000000    1    0.00000000    0
 C                  4    2.45854269    3  103.13597413    2   62.19088628    0
 C                  5    1.41263246    4   30.96712274    3 -114.96688053    0
 C                  5    2.47345678    4  155.57277852    3   -3.95739525    0
 C                  7    1.40192800    5   31.36445834    4  -67.05177346    0
 C                  8    1.47023488    7  118.88012120    5  133.96696254    0
 C                  9    1.41263246    8  119.23313037    7  178.98716443    0
 C                  7    2.38756302    5  101.23515048    4    3.92909825    0
 C                 11    1.40192800    7   90.00000000    5  -29.47652788    0
 C                 12    1.47023488   11  118.88012120    7  111.98348127    0
 C                 13    1.41263246   12  119.23313037   11  178.98716443    0
 C                 11    2.38756302    7   90.00000000    5   60.52347212    0
 C                 15    1.40192800   11   90.00000000    7  -90.00000000    0
 C                 16    1.47023488   15  118.88012120   11  111.98348127    0
 C                 17    1.41263246   16  119.23313037   15  178.98716443    0
 C                 15    2.38756302   11   90.00000000    7    0.00000000    0
 C                 19    1.40192800   15   90.00000000   11  -90.00000000    0
 C                 19    2.48710480   15  101.72503377   11   60.64513898    0
 C                 21    1.41263246   19   31.05462349   15 -108.16385345    0
 C                 21    1.44360564   19  134.93861618   15  -37.90663231    0
 C                 23    1.44360564   21  112.67175768   19   -1.82333415    0
 C                 24    1.41263246   23  118.80062827   21  -31.82335089    0
 C                 24    1.44360564   23  101.38056080   21  100.35603013    0
 C                 26    1.44360564   24  112.67175768   23 -100.35603013    0
 C                 27    1.41263246   26  118.80062827   24  -31.82335089    0
 C                 27    1.44360564   26  101.38056080   24  100.35603013    0
 C                 29    1.44360564   27  112.67175768   26 -100.35603013    0
 C                 30    1.41263246   29  118.80062827   27  -31.82335089    0
 C                 21    1.44360564   19   87.91301483   15   66.13240820    0
 H                  1    1.08676157    6  120.73303602    5  174.96459862    0
 H                  4    1.08676157    3   93.81889728    2  -93.82740845    0
 H                  2    1.08676157    1   93.81889728    6 -126.09599138    0
 H                  3    1.08676157    2   93.81889728    1  -93.82740845    0
 H                 29    1.08676157   27  120.73303602   26   52.85602036    0
 H                 26    1.08676157   24  120.73303602   23   52.85602036    0
 H                 32    1.08676157   21  120.73303602   19  171.61058920    0
 H                 23    1.08676157   21  120.73303602   19  151.38871634    0
 X                 15    1.82799866   11   49.22775544    7  -30.42058102    0
 Li                41    0.00000001   15  112.54815565   11 -110.97981054    0

 1 6 1.5 10 1.5 33 1.0
 2 10 1.5 14 1.5 35 1.0
 3 14 1.5 18 1.5 36 1.0
 4 6 1.5 18 1.5 34 1.0
 5 6 1.5 8 1.0 20 1.0
 6
 7 8 1.5 22 1.0 25 1.0
 8 9 1.0
 9 10 1.5 12 1.0
 10
 11 12 1.5 25 1.0 28 1.0
 12 13 1.0
 13 14 1.5 16 1.0
 14
 15 16 1.5 28 1.0 31 1.0
 16 17 1.0
 17 18 1.5 20 1.0
 18
 19 20 1.5 22 1.0 31 1.0
 20
 21 22 1.5 23 1.5 32 1.5
 22
 23 24 1.5 40 1.0
 24 25 1.5 26 1.5
 25
 26 27 1.5 38 1.0
 27 28 1.5 29 1.5
 28
 29 30 1.5 37 1.0
 30 31 1.5 32 1.5
 31
 32 39 1.0
 33
 34
 35
 36
 37
 38
 39
 40
 41

Answer 1

fpath = os.path.join(thisdir, filename)
with open(fpath, 'r+') as f:
    lines = f.readlines()
    f.seek(0)
    f.truncate()
    for line in lines:
        if '0 2' in line:
            for test in filelist:
                pathmatch = file_match(line, test)
                    if pathmatch is not None: 
                        repstring = filelist[test] + pathmatch
                        line = line.replace(test, repstring)
        f.write(line)

one weird thing is you will have to make copy of you files before running above code otherwise you may loose your original code

A (relatively) safe way to replace a line in a file.

enter code here

#!/usr/bin/python 
# defensive programming style
# function to replace a line in a file
# and not destroy data in case of error

def replace_line(filepath, oldline, newline ):
  """ 
  replace a line in a temporary file, 
  then copy it over into the 
  original file if everything goes well

  """

 # quick parameter checks 
  assert os.exists(filepath)          # ! 
  assert ( oldline and str(oldline) ) # is not empty and is a string
  assert ( newline and str(newline) )

  replaced = False
  written  = False

  try:

    with open(filepath, 'r+') as f:    # open for read/write -- alias to f       

      lines = f.readlines()            # get all lines in file

      if oldline not in lines:
          pass                         # line not found in file, do nothing

      else:
        tmpfile = NamedTemporaryFile(delete=True)  # temp file opened for writing

        for line in lines:           # process each line
          if line == oldline:        # find the line we want 
            tmpfile.write(newline)   # replace it 
            replaced = True  
          else:
            tmpfile.write(oldline)   # write old line unchanged

        if replaced:                   # overwrite the original file     
          f.seek(0)                    # beginning of file
          f.truncate()                 # empties out original file

          for tmplines in tmpfile: 
            f.write(tmplines)          # writes each line to original file
          written = True  

      tmpfile.close()              # tmpfile auto deleted    
      f.close()                          # we opened it , we close it 

  except IOError, ioe:                 # if something bad happened.
    printf ("ERROR" , ioe)
    f.close()                        
    return False

  return replaced and written        # replacement happened with no errors = True 

(note: this replaces entire lines only , and all of the lines that match in the file)