Python - search for string, extract number from line and append to list

Question

I am working with a STEP file format which I want to parse, extract information and store it in arrays so I can call upon and perform mathematical operations on them later in the program.

Below is an example of the data I am working with (advanced_face references face_outer_bound later in the data file:

#12 = ADVANCED_FACE ( 'NONE', ( #194 ), #326, .F. ) ;
...
#194 = FACE_OUTER_BOUND ( 'NONE', #159, .T. ) ;

Here's what I have come up with so far:

import re

with open('TestSlot.STEP', 'r') as step_file:
        data = step_file.readlines()

NF = 0
faces = []
for line in data:
        line = line.strip()
        if re.search("ADVANCED_FACE", line):
                NF = NF + 1
                advface = re.compile('#\d+')
                advfaceresult = advface.match(line)
                faces.append(advfaceresult.group())

print("Face IDs =", faces)
print("Number of faces, NF =", NF)

This gives the output:

Face IDs = ['#12', '#73', '#99', '#131', '#181', '#214', '#244', 
'#273', '#330', '#358']
Number of faces, NF = 10

How would I go about stripping the regex match so only the number is appended to the list?

Answer 1

You can use group within regex and convert directly string '12' to number 12 before append to faces list advface = re.compile('#(\d+)') advfaceresult = advface.match(line) faces.append(int(advfaceresult.group(1)))

the result will be Face IDs = [12, ...]

Also solution can be reached by

import re
ifile = r'TestSlot.STEP'
with open(ifile) as f:
    text = f.read()  # read all text
    faces_txt = re.findall(r'#(\d+) = ADVANCED_FACE.*;', text)
    #  get all groups by re
    faces = [int(face) for face in faces_txt]   # convert to int
    print('Face IDs = ', faces)
    print('Number of faces, NF =', len(faces))