Why will node include annotation when i use 2to3/lib2to3/fix_print.py

Question

python file

# -*- coding: utf-8 -*- print 'original python file'

fix_print.py

class FixPrint(fixer_base.BaseFix): BM_compatible = True PATTERN = """ simple_stmt< any* bare='print' any* > | print_stmt """ def transform(self, node, results): assert results bare_print = results.get("bare")

when i use 2to3/lib2to3/fix_print.py to transform the python file.

if i print the node,it shows

# -*- coding: utf-8 -*- print 'original python file'

why does the node include the annotation "# -- coding: utf-8 --"

Thank you very much if you can explain this.

Presumably because you can't make sense of any non-ASCII characters unless you know the encoding. — tripleee
– tripleee, Commented Jun 24, 2024 at 9:15

Aemyl · Accepted Answer · 2024-06-24 09:17:52Z

1

# -*- coding: utf-8 -*-

This comment has a special meaning to the Python interpreter, as defined by PEP 263 - Defining Python Source Code Encodings. It tells the interpreter that the current file is encoded with UTF-8, not just the string that is printed. In other words, it isn't an annotation for the print statement that follows it.

answered Jun 24, 2024 at 9:17

Aemyl

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4 Comments

haifu_qin Over a year ago

If there is any other codes before print, I print node It will only shows print original python file If there is only # -*- coding: utf-8 -*- before print. I print node It will only shows # -*- coding: utf-8 -*- print 'original python file'

haifu_qin Over a year ago

do you know the reason about this?

Aemyl Over a year ago

Honestly I don't know if I understood you correctly, but my guess is that comments become part of the first statement after it. If you insert other statements between the comment and the print statement, the comment will become part of the first inserted statement. the FixPrint class is only used for print nodes, so it doesn't print these inserted nodes and their comments.

haifu_qin Over a year ago

thank you very much,maybe you are right.

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