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The file method read does not "see" CR


Chris,

Many thanks. The first part of your answer was spot on. I have modified the
program, opening its input file in "rb" mode, and now the program is
working as I intend it to.

I am puzzled by the second part, where you say that the read call will
return one character, if the file is in text mode.

I was expecting this statement to read

   The read call will return one byte if the file is in binary mode.

Given that I *was *opening the file in "r" mode (which, I am assuming, is
"text" mode), then, if your statement is true, I have two more questions:

   1. If CR is a character and I open the file in text mode, then why does
the program not "see" the CR characters?

   2. Does the program not see CR characters under these circumstances
because they do not "count" as characters or for some other reason?

(You have probably spotted that this question 1 is virtually the same as my
original question.)

Stephen.














On Tue, Dec 10, 2019 at 10:39 AM Chris Angelico <rosuav at gmail.com> wrote:

> On Tue, Dec 10, 2019 at 9:17 PM Stephen Tucker <stephen_tucker at sil.org>
> wrote:
> >
> > I am running Python 2.7.10 on a Windows 10 machine. I have written a
> Python
> > program that counts occurrences of bytes in a text file and have run it
> on
> > a small test file. This file has CR-LF sequences at the ends of its
> lines.
> > The Python program counted the LF bytes, but didn't count any CR bytes.
> > Given that the documentation for the read method claims that exactly size
> > bytes are read by each call to the method (in this case, size is 1) does
> > this behaviour constitute a bug?
> >
>
> Are you trying to treat the file as text, or bytes? Are you looking
> for occurrences of bytes, or characters? Make a decision on that, then
> code accordingly. If you want to look for bytes, then open the file in
> binary mode and read it as bytes. If you want to look for characters,
> then you probably shouldn't care about which sort of line ending it
> is, but if you really do, then disable newline processing and examine
> the end of each logical line.
>
> The read call will return one character, if the file is in text mode.
>
> ChrisA
> --
> https://mail.python.org/mailman/listinfo/python-list
>