On Sun, 8 May 2022 22:48:32 +0200, Marco Sulla
<marco.sulla.pyt...@gmail.com> declaimed the following:
>
>Emh. I re-quote
>
>seek(offset, whence=SEEK_SET)
>Change the stream position to the given byte offset.
>
>And so on. No mention of differences between text and binary mode.
You ignore that, underneath, Python is just wrapping the C API... And
the documentation for C explicitly specifies that other then SEEK_END with
offset 0, and SEEK_SET with offset of 0, for a text file one can only rely
upon SEEK_SET using an offset previously obtained with (C) ftell() /
(Python) .tell() .
https://docs.python.org/3/library/io.html
"""
class io.IOBase
The abstract base class for all I/O classes.
"""
seek(offset, whence=SEEK_SET)
Change the stream position to the given byte offset. offset is
interpreted relative to the position indicated by whence. The default value
for whence is SEEK_SET. Values for whence are:
"""
Applicable to BINARY MODE I/O: For UTF-8 and any other multibyte
encoding, this means you could end up positioning into the middle of a
"character" and subsequently read garbage. It is on you to handle
synchronizing on a valid character position, and also to handle different
line ending conventions.
"""
class io.TextIOBase
Base class for text streams. This class provides a character and line
based interface to stream I/O. It inherits IOBase.
"""
seek(offset, whence=SEEK_SET)
Change the stream position to the given offset. Behaviour depends on
the whence parameter. The default value for whence is SEEK_SET.
SEEK_SET or 0: seek from the start of the stream (the default);
offset must either be a number returned by TextIOBase.tell(), or zero. Any
other offset value produces undefined behaviour.
SEEK_CUR or 1: “seek” to the current position; offset must be zero,
which is a no-operation (all other values are unsupported).
SEEK_END or 2: seek to the end of the stream; offset must be zero
(all other values are unsupported).
"""
EMPHASIS: "offset must either be a number returned by TextIOBase.tell(), or
zero."
TEXT I/O, with a specified encoding, will return Unicode data points,
and will handle converting line ending to the internal (<lf> represents
new-line) format.
Since your code does not specify BINARY mode in the open statement,
Python should be using TEXT mode.
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