Python：使用re模块查找字符串，然后在字符串下打印值

Question

I am attempting to use the re module to search a string of a fairly large file. The file I am searching has the following format:

      220
      BOX 1,  STEP 1
      C        15.1760586379       13.7666285127        4.1579861659
      F        13.7752750995       13.3845518556        4.1992254467
      F        15.1122807811       15.0753387163        3.8457966464
      H        15.5298304628       13.5873563855        5.1615910859
      H        15.6594416869       13.1246597008        3.3754112615
        5
     BOX 2,  STEP 1
     C        15.1760586379       13.7666285127        4.1579861659
     F        13.7752750995       13.3845518556        4.1992254467
     F        15.1122807811       15.0753387163        3.8457966464
     H        15.5298304628       13.5873563855        5.1615910859
     H        15.6594416869       13.1246597008        3.3754112615
       240
     BOX 1,  STEP 2
     C        12.6851133069        2.8636250164        1.1788963097
     F        11.7935769268        1.7912366066        1.3042188034
     F        13.7887138736        2.3739304018        0.4126088380
     H        12.1153838312        3.7024696077        0.7164304431
     H        13.0962656950        3.1549047758        2.1436863477
     C        12.6745394723        3.6338848332       15.1374252921
     F        11.8703828307        4.3473226569       16.0480492173
     F        12.2304604843        2.3709059503       14.9433964493
     H        12.6002811971        4.1968554204       14.1449118786
     H        13.7469256153        3.6086212350       15.5204655285

This format continues on for Box 1 and Box 2 for ~30000 STEPS total, for each BOX. I have code that utilizes the re module to searches this file based on the keyword "STEP". Unfortunately, it does not yield any results when I run it. I need my code to search 1) for ONLY Box 1, then 2) print/output all the coordinates(preferably omitting the "C's, F's, H's"; so only the coordinates) beginning after STEP 1 to a file, 3) increment the "STEP" number by 48 and then repeat 2). I also want to ignore the "5" and the "240" in the file that I am searching; so the code should compensate so that this is not included in the output after we search this file. This is what I have thus far (it does not work):

 import re
 shakes = open("mc_coordinates", "r")
 i = 1
 for line in shakes:
        if re.match("(.*)STEP i(.*)", line):
               print line
        i+=48

This is an example of what I what my code to do:

  STEP 1
    15.1760586379       13.7666285127        4.1579861659
    13.7752750995       13.3845518556        4.1992254467
    15.1122807811       15.0753387163        3.8457966464
    15.5298304628       13.5873563855        5.1615910859
    15.6594416869       13.1246597008        3.3754112615  
  STEP 49
    12.6851133069        2.8636250164        1.1788963097
    11.7935769268        1.7912366066        1.3042188034
    13.7887138736        2.3739304018        0.4126088380
    12.1153838312        3.7024696077        0.7164304431
    13.0962656950        3.1549047758        2.1436863477
    12.6745394723        3.6338848332       15.1374252921
    11.8703828307        4.3473226569       16.0480492173
    12.2304604843        2.3709059503       14.9433964493
    12.6002811971        4.1968554204       14.1449118786
    13.7469256153        3.6086212350       15.5204655285
  STEP 97
    15.1760586379       13.7666285127        4.1579861659
    13.7752750995       13.3845518556        4.1992254467
    15.1122807811       15.0753387163        3.8457966464
    15.5298304628       13.5873563855        5.1615910859
    15.6594416869       13.1246597008        3.3754112615  

It should be noted that this is a condensed version, typically there will be ~250 lines of coordinates in between "STEP" numbers. Any ideas or thought will be appreciated. Thanks!!

Answer 1

A quick although maybe not efficent way is to just parse line by line and add some states.

# untested code, but i think you get the idea
import re
shakes = open("mc_coordinates", "r")
i = 1
output = False # are we in a block that should be output?
for line in shakes:
    if re.match("(.*)STEP i(.*)", line): # tune this to match only for BOX 1
        print line
        output = true
        i+=48
    elif re.match("(.*)STEP i(.*)", line):
        # some other box or step
        output = false
    elif output:
        print line # or remove the first few chars to get rid of C,F or Hs.

Answer 2

It seems like the easiest way to do this would be to have two regex patterns: 1. Find the 'BOX 1, STEP 48N+1' string. 2. Get the coordinates.

I'm providing some code below. Haven't tried it on your stuff but it should be easy to fix the bugs. Basically, what you need is a small state machine that tells you when you should and should not print out the coordinates

step_re = re.compile(r'BOX 1,\s+STEP (\d+)')
coord_re = re.compile(r'\s*(\d+.\d+)'*3)
in_step = False
for line in io.open('your_file.txt', rb):
  if in_step:
    coord_match = coord_re.search(line)
    if coord_match:
      print coord_match.group(1), coord_match.group(2), coord_match.group(3)
    else:
      in_step = False
    continue

  step_match = step_re.match(line)
  if step_match and (int(step_match.group(1)) % 48) == 1:
    print 'STEP {}'.format(step_match.group(1))
    in_step = True