How to delete a symbol from file by its position

Question

I need to delete a symbol from txt file by its position in file. For example, there is a text file sample.txt:

Hello, world!
Abcdef
hello
world

and I need to delete a character , that is located on the sixth position: pos = 6

I tried to use this code:

pos = 6

with open('sample.txt', 'r+') as f:
    f.seek(pos - 1) # move to the position before ,
    print(f.read(1)) # print the , character
    f.seek(pos - 1) # return back to the position before ,
    f.write('\r')
    f.close()

This prints ,, like I expected but file now looks like this:

Hello
 world!
Abcdef
hello
world

So my code replaced the , character with a new line symbol \n, instead of carriage return symbol \r.

UPD:

My solution replaces the , symbol with symbol with ASCII code 13 (0D), that doesn't solve my problem:

I get an error from `f.seek(-1, 1)` if the file isn't opened in binary mode. — Barmar, Jul 31 '23 at 21:14
And then it requires calling that I write a byte string, not a regular string. — Barmar, Jul 31 '23 at 21:14
See https://stackoverflow.com/questions/53001901/unsupportedoperation-cant-do-nonzero-cur-relative-seeks-python — Barmar, Jul 31 '23 at 21:15
Yes, sorry, I edited this like `f.seek(pos - 1)`, and now it should work — TimKostenok, Jul 31 '23 at 21:16
It might just be that the way you're viewing the file shows a CR as a newline. Try viewing the file with a hex editor. — Barmar, Jul 31 '23 at 21:17
I used windows when did it, an I use a VSCode viewer of files — TimKostenok, Jul 31 '23 at 21:19
In a hex editor it shows like 0D and so my solution doesn't solve my problem because it doesn't remove the symbol, and just replace it with symbol with ASCII code 13. — TimKostenok, Jul 31 '23 at 21:22

score 1 · Accepted Answer · answered Jul 31 '23 at 21:24

VSCode is showing the CR as a newline.

To remove it entirely, don't overwrite it with a single character. Read the rest of the file into a variable, seek back to the position, then overwrite from the variable.

pos = 6

with open('sample.txt', 'r+') as f:
    f.seek(pos - 1) # move to the position before ,
    print(f.read(1)) # print the , character
    rest = f.read() # read the rest of the file
    f.seek(pos - 1) # return back to the position before ,
    f.write(rest)
    f.truncate() # adjust the end of the file

BTW, you don't need f.close(), that's done automatically when you use with.

How to delete a symbol from file by its position

1 Answers1