How to delete multiple lines together from another python file using a python file?

Question

Now, I know this kind of question has been kind asked before, but this is slightly different.
I want to use a file main.py to remove MULTIPLE lines from another file targetfile.py
These multiple lines are all together, like:

line_To_Delete1
line_To_Delete2
line_To_Delete3
line_To_Replace1

All these lines will have the comments #del1 , #del2 or something that indentifies it as unique, and the one to delete/replace.
So how do I delete all these lines together?
Also, I want to replace the 4th line with some other line.
How do I do all this?

How do you know which lines to delete?

Mike67
– Mike67

2020-09-08 00:23:57 +00:00
Commented Sep 8, 2020 at 0:23 — Mike67
– Mike67, Commented Sep 8, 2020 at 0:23
@Mike67 I have added more details to the question

Zelix75
– Zelix75

2020-09-08 06:25:05 +00:00
Commented Sep 8, 2020 at 6:25 — Zelix75
– Zelix75, Commented Sep 8, 2020 at 6:25

Mike67 · Accepted Answer · 2020-09-09 19:17:28Z

1

To remove lines from a file based on a condition, you can just read the lines from the one file then write them to another if the condition is false.

Try this code:

txt = '''
print(1)
print(2)
print(3)  #del1
print(4)  #del2
print(5)  #rep1
print(6)
print(7)
'''.strip()

with open("targetfile.py",'w') as f:  # write test file
    f.write(txt)

######### main script #########

repstr = "NewText"

outstr = ""
with open("targetfile.py") as f1:
   for ln in f1.readlines():
      if "#rep" in ln:    # condition to replace line
          outstr += repstr + '\n'
      elif not "#del" in ln:  # condition to copy line
          outstr += ln
             
with open("targetfile.py",'w') as f2:  # overwrite file
    f2.write(outstr)

Output (targetfile.py)

print(1)
print(2)
NewText
print(6)
print(7)

edited Sep 9, 2020 at 19:17

answered Sep 8, 2020 at 19:29

Mike67

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4 Comments

Zelix75 Over a year ago

How do I do it without creating a new file? And how do I replace specific lines?

Zelix75 Over a year ago

Great answer. Just one last question. If I already have a text file that is in ANOTHER directory, and I enter the path in open(), will it still work?

Mike67 Over a year ago

yes - something like open('c:/tmp/myfile.py') should work fine.

Zelix75 Over a year ago

I know I could get into trouble for writing this, but Thank You so Much. Man, this was so very important to me, and you made my day with this solution. Anyone can delete this comment or downvote my question, but it'll be worth it. Thank You so much.

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