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Delete multiple lines from txt file - Printable Version

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Delete multiple lines from txt file - Lky - Jul-09-2022

Does anyone know how to delete lines in txt file according to user input without using any list or dictionary?

For example content inside txt file:
Question 1 Which is correct?
A. X
B. XX
C. XXX
D. XXXX
Question 2 Which is wrong?
A. X
B. XX
C. XXX
D. XXXX
Question 3 Which is True?
A. X
B. XX
C. XXX
D. XXXX

When user choose to delete question 2, the file will updated and the output will become like this:
Question 1 Which is correct?
A. X
B. XX
C. XXX
D. XXXX
Question 3 Which is True?
A. X
B. XX
C. XXX
D. XXXX

RE: Delete multiple lines from txt file - ibreeden - Jul-09-2022

The best way to do this is:
  1. Copy the lines of the original file to a temporary file, but don't copy the lines you do not want.
  2. If no errors occurred: remove the original file.
  3. Rename the temporary file to the name of the original file.


RE: Delete multiple lines from txt file - jcrubaugh45 - Jul-10-2022 

def remove_lines_list (file):
    ip_list = open(file).readlines()
    return [address.rstrip('\n') for address in ip_list]
I use this function to take a list of IP addresses and remove all the trailing \n so i get a clean list with no extra spaces or lines.. i dont know if this is helpful but i use this when getting a txt file in put of IP addresses i need to loop through.

RE: Delete multiple lines from txt file - Lky - Jul-10-2022

(Jul-09-2022, 06:00 PM)ibreeden Wrote: The best way to do this is:
  1. Copy the lines of the original file to a temporary file, but don't copy the lines you do not want.
  2. If no errors occurred: remove the original file.
  3. Rename the temporary file to the name of the original file.
What will be the condition for A. B. C. D.?

RE: Delete multiple lines from txt file - Lky - Jul-10-2022

(Jul-10-2022, 12:09 AM)jcrubaugh45 Wrote: 
def remove_lines_list (file):
    ip_list = open(file).readlines()
    return [address.rstrip('\n') for address in ip_list]
I use this function to take a list of IP addresses and remove all the trailing \n so i get a clean list with no extra spaces or lines.. i dont know if this is helpful but i use this when getting a txt file in put of IP addresses i need to loop through.
It can't work as I need to delete the whole question not only one line.

RE: Delete multiple lines from txt file - ibreeden - Jul-10-2022

(Jul-10-2022, 05:32 AM)Lky Wrote: What will be the condition for A. B. C. D.?
Introduce a boolean variable e.g. "do_copy". If this variabel is true, copy the line. Else not.
When a line contains: "Question 2 " then toggle the variable to False.
When a line contains: "Question" then toggle the variable to True.

RE: Delete multiple lines from txt file - jefsummers - Jul-10-2022

That should work, as long as Question does not appear in any answers. Basically using a flag that is unique to the category of line Question.
Suggest also - do this in memory, with option of displaying output, then do the write after approval. Skips the swap part, or you can allow user to Save As with a different filename. Adds a little versatility