UnsupportedOperation: can't do nonzero cur-relative seeks : Python

Question

Below is my code, I am using :

with open(r'C:\Users\Manish\Desktop\File5.txt', 'r') as f:
     fo = f.read(20)
     print(fo)
     f.seek(20,1)
     fo = f.read(20)
     print(fo)

But instead of getting next lines from current position, it repeatedly showing me error. Where is the problem in my code ?

1) This is first line. 2) This is second line. 3) This is third line. 4) This is fourth line. 5) This is fifth line. 6) This is sixth line. 7) This is seventh line. 8) This is eighth line. 9) This is ninth line. 10) This is tenth line. — Manish Pal, Oct 26 '18 at 05:29
Possible duplicate of [Seeking from end of file throwing unsupported exception](https://stackoverflow.com/questions/21533391/seeking-from-end-of-file-throwing-unsupported-exception) — Janne Karila, Oct 26 '18 at 08:01

score 9 · Accepted Answer · edited Jan 31 '21 at 06:07

9

It seems like offset from current stream and end of stream only supported in binary mode. Which you have to open the file with

open(r'C:\Users\Manish\Desktop\File5.txt', 'rb')

edited Jan 31 '21 at 06:07

MaxV

2,601
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answered Jan 30 '21 at 20:49

Xenox Inno

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score -1 · Answer 2 · edited Nov 09 '21 at 17:09

-1

Syntax:

f.seek(offset, from_what), where f is file pointer

Parameters:

Offset: Number of positions to move forward from_what: It defines point of reference.

Returns:

Does not return any value

The reference point is selected by the from_what argument. It accepts three values:

0: sets the reference point at the beginning of the file

1: sets the reference point at the current file position

2: sets the reference point at the end of the file

By default from_what argument is set to 0. Note: Reference point at current position / end of file cannot be set in text mode except when offset is equal to 0.

edited Nov 09 '21 at 17:09

Glauco

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answered Nov 09 '21 at 16:27

EduCBSE By Jasmine

1

It looks okay but it might be too educative, I think it would be best to point out what the error is, and then educate. In that answer there is no clear "answer" to the problem, only documentation – Nathan Marotte Nov 09 '21 at 18:01
seek method returns the new absolute position. – yrnr Sep 09 '22 at 03:02
This doesn't answer the question. It's just documentation. – Arpan Srivastava Jul 18 '23 at 10:58

UnsupportedOperation: can't do nonzero cur-relative seeks : Python

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