a script to indent lines of text based on given start tag and end tag

indent.py

# a script to indent lines of text based on given start tag and end tag 
import os
import os.path 

src_file = r"<sourcefile>" 
dst_file = r"<destination-file>"

with open(src_file,"rb") as srcfile:
    content = srcfile.read()

lines = content.splitlines()

START_TAG = "_START"
END_TAG = "_END" 
INDENTATION = "    "
num_indentation = 0 


with open(dst_file,mode="wb") as file:
    for line in lines:
        #print("line:",line)
        linestr = line.decode("utf-8")
        if linestr.find(START_TAG) >= 0:
            print("met start TAG")
            linestr = INDENTATION*num_indentation + linestr

            num_indentation += 1 
        elif linestr.find(END_TAG) >= 0: 
            print("met END TAG")
            num_indentation -= 1 
            linestr = INDENTATION*num_indentation + linestr
        else:     
            linestr = INDENTATION*num_indentation + linestr 
             

        
        file.write(bytearray(linestr,"utf-8"))
        file.write(b"\n") 

    

print("done.")