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From: Ben Finney <ben+python@benfinney.id.au>
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Subject: Re: non printable (moving away from Perl)
Date: Sat, 12 Mar 2016 06:52:42 +1100
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Fillmore <fillmore_remove@hotmail.com> writes:

> On 3/11/2016 2:23 PM, MRAB wrote:
> > Python 3 (Unicode) strings have an .isprintable method:
> >
> > mystring.isprintable()
>
> my strings are UTF-8. Will it work there too?

You need to always be clear on the difference between text (the Python 3
‘str’ type) versus bytes.

It only makes sense to talk about an encoding, when talking about bytes.

Text itself is an abstract data type; the content of a Unicode string
does not have any encoding because it is not encoded.

The content of a byte stream (such as a file's content) is not text, it
is bytes.

    >>> foo = "こんにちは"
    >>> foo.isprintable()
    True

    >>> foo_encoded = foo.encode("utf-8")
    >>> foo_encoded.isprintable()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: 'bytes' object has no attribute 'isprintable'

You can only ask ‘isprintable’ about text. Bytes are not printable
because bytes are not text; you need to decode the bytes to text before
asking whether that text is printable.

    >>> infile = open('lorem.txt', 'rb')
    >>> infile_bytes = infile.read()
    >>> infile_bytes.isprintable()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    AttributeError: 'bytes' object has no attribute 'isprintable'

    >>> infile = open('lorem.txt', 'rt', encoding="utf-8")
    >>> infile_text = infile.read()
    >>> infile_text.isprintable()
    True

-- 
 \        “Telling pious lies to trusting children is a form of abuse, |
  `\                    plain and simple.” —Daniel Dennett, 2010-01-12 |
_o__)                                                                  |
Ben Finney