So here I am, I read about encoding all day, now I need some clarification.
First off I'm using eclipse mars with pydev.
Unicode is a (character set + code points), basicaly a table of symbols associated with numerical value.
The way those value are going to be stored at a binary level are defined by the encoding, let's say UTF-8.
1 : shebang
What is the shebang for? when I put # -*- coding: utf-8 -*- does it do something? or does it just indicate that my file is encoded in UTF-8 (but since it's just an indication it could be a lie :o)
2 : Eclipse file encoding
After I wrote my shebang and saved I went into the property of the file, and it said encoding : ISO-8859-1, so my guess is that the shebang does nothing beside indicate in which encoding my file is.
Do I need to manually set every files to UTF-8 or is there a way to teach eclipse to read the shebang and act accordingly.
3 : Why does the shebang only specify the encoding?
My shebang say utf-8, ok right, so what? it does not tell me which caracter set is used.
Since UTF-8 is just an encoding I could use UTF-8 with any character set no?
I could encode ASCII in UTF-8 if I wanted, since an encoding is just a way to convert and store/read code points.
What if my character set encoded in utf-8 does not have the same code points than unicode? (is this possible?)
4 : maybe a solution?
I oftenly read that utf-8 is an implementation of unicode, does that mean that each times you read encoding = UTF-8 you can be 100%, and I say 100%, sure that the characterset+code points is unicode?
I'm lost
There are multiple misconceptions in your question.
Unicode is a standard that is commonly used for working with text. It is not "character set + code points" e.g., Unicode standard defines how to find word boundaries or how to compare Unicode string.
# -*- coding: utf-8 -*- is an encoding declaration. It is not a shebang. Shebang (as it name suggests) starts with #! e.g., #! /usr/bin/env python.
You might need the encoding declaration if there are non-ascii literal characters in your Python source code e.g., you don't need an encoding declaration if you write:
#!/usr/bin/env python2
print u"\N{SNOWMAN}"
But you need it if you use literal non-ascii characters:
#!/usr/bin/env python2
# -*- coding: utf-8 -*-
print u"☃"
Both scripts produce the same output if the second script is saved using utf-8 encoding. The encoding declaration says how to interpret bytes that constitute the Python source code to get the program text.
"is there a way to teach eclipse to read the shebang encoding declaration and act accordingly." is a good separate question. If IDE has explicit Python support then it should do it automatically.
My shebang encoding declaration say utf-8, ok right, so what? it does not tell me which character set is used.
"character encoding", codepage, and charset may be used interchangeably in many contexts. See What's the difference between encoding and charset? The distinctions are irrelevant for the task of converting from bytes to text and back in Python:
unicode_text = bytestring.decode(character_encoding)
bytestring = unicode_text.encode(character_encoding)
A bytestring is an immutable sequence of bytes in Python (roughly speaking numbers in 0..255 range) that is used to represent arbitrary binary data e.g., images, zip-archives, encrypted data, and text encoded using some character encoding. A Unicode string is an immutable sequence of Unicode codepoints (roughly speaking, numbers in 0..sys.maxunicode range) that is used to represent text in Python.
Some character encodings such as cp437 support only a few Unicode characters. Others such as utf-8 support the full range of Unicode codepoints.
The right way to add the encoding declaration is > # -*- coding: utf-8 -*-
It tells python to change the encoding in the current script to UTF-8 it has nothing to do with the user .
Ok I think I found an awnser to all those questions
1/
thanks to J.Dev, the shebang only tells the python interpreter in what the file is encoded, but YOU have to encode the file in what you put in the shebang
2/
Apparently I have to do it manually
3/
Because an encoding is associated with a charset, if you say encoding=utf-8 then it will always be a unicode charset
Some old 1 byte charset don't have encoding, you don't need encoding since the char are all stored on 1 byte, the natural binary translation is the encoding.
So when you say ASCII for instance you mean the charset and encoding = ASCII
But this leave me wondering, is there other type of charset out there with multiple encoding implementation (like unicode can be encoded in utf-8/16/32)
Related
I am trying to print a clean chess board in python 2.7 that uses unique characters such as ♟.
I have tried simply replacing a value in a string ("g".replace(g, ♟)) but it is changed to '\xe2\x80\xa6'. If I put the character into an online ASCII converter, it returns "226 153 159"
♟ is a unicode character. In python 2, str holds ascii strings or binary data, while unicode holds unicode strings. When you do "♟" you get a binary encoded version of the unicode string. What that encoding is depends on the editor/console you used to type it in. Its common (and I think preferred) to use UTF-8 to encode strings but you may find that Windows editors favor little-endian UTF-16 strings.
Either way, you want to write your strings as unicode as much as possible. You can do some mix-and-matching between str and unicode but make sure anything outside of the ASCII code set is unicode from the beginning.
Python can take an encoding hint at the front of the file. So, assuming you use a UTF-8 editor, you can do
!#/usr/bin/env python
# -*- coding: utf-8 -*-
chess_piece = u"♟"
print u"g".replace(u"g", chess_piece)
When doing the following concatenation:
a = u'Hello there '
b = 'pirate ®'
c = a + b # This will raise UnicodeDecodeError
in python 2, 'pirate ®' is automatically converted to unicode type through ascii encoding. And since there is a non-ascii unicode sequence (®) in the string, it will fail.
Is there a way to change this default encoding to utf8?
It is possible, although it's considered a hack. You have to reload sys:
import sys
reload(sys)
sys.setdefaultencoding('utf-8')
See this blog post for some explanation of the potential issues this raises:
http://blog.startifact.com/posts/older/changing-the-python-default-encoding-considered-harmful.html
It may be the only option you have, but you should be aware that it can lead to further problems. Which is why it's not a simple and easy thing to set.
From the Python Unicode Howto:
Ideally, you’d want to be able to write literals in your language’s natural encoding. You could then edit Python source code with your favorite editor which would display the accented characters naturally, and have the right characters used at runtime.
Python supports writing Unicode literals in any encoding, but you have to declare the encoding being used. This is done by including a special comment as either the first or second line of the source file:
#!/usr/bin/env python
# -*- coding: latin-1 -*-
u = u'abcdé'
print ord(u[-1])
suffixes = {
1: ["ो", "े", "ू", "ु", "ी", "ि", "ा"]}
When I done
message given by IDLE is
Unsupported characters in input
Also not see the proper font in MS-DOS.
What encoding is your source file in?
If it is UTF8, put the comment
# -*- coding: utf-8 -*-
at the top of the file.
If you don't declare encoding in your first or second line in your python source file, then the python interpreter will use ASCII encoding system to decode the characters in the file. As these characters you used couldn't be decoded by ASCII encoding system, errors happended.
The solution is as #RemcoGerlich said. Here is the doc.
The encoding is used for all lexical analysis, in particular to find the end of a string, and to interpret the contents of Unicode literals. String literals are converted to Unicode for syntactical analysis, then converted back to their original encoding before interpretation starts. The encoding declaration must appear on a line of its own.
This seems to be a known bug in the 2.x IDLE console: http://bugs.python.org/issue15809. A fix was made for Python 3.x, but doesn't appear to be backported.
Instead, use an alternative console, such as iPython/Jupyter, or a fully-fledged IDE, such as PyCharm.
Say I have a function:
def NewFunction():
return '£'
I want to print some stuff with a pound sign in front of it and it prints an error when I try to run this program, this error message is displayed:
SyntaxError: Non-ASCII character '\xa3' in file 'blah' but no encoding declared;
see http://www.python.org/peps/pep-0263.html for details
Can anyone inform me how I can include a pound sign in my return function? I'm basically using it in a class and it's within the '__str__' part that the pound sign is included.
I'd recommend reading that PEP the error gives you. The problem is that your code is trying to use the ASCII encoding, but the pound symbol is not an ASCII character. Try using UTF-8 encoding. You can start by putting # -*- coding: utf-8 -*- at the top of your .py file. To get more advanced, you can also define encodings on a string by string basis in your code. However, if you are trying to put the pound sign literal in to your code, you'll need an encoding that supports it for the entire file.
Adding the following two lines at the top of my .py script worked for me (first line was necessary):
#!/usr/bin/env python
# -*- coding: utf-8 -*-
First add the # -*- coding: utf-8 -*- line to the beginning of the file and then use u'foo' for all your non-ASCII unicode data:
def NewFunction():
return u'£'
or use the magic available since Python 2.6 to make it automatic:
from __future__ import unicode_literals
The error message tells you exactly what's wrong. The Python interpreter needs to know the encoding of the non-ASCII character.
If you want to return U+00A3 then you can say
return u'\u00a3'
which represents this character in pure ASCII by way of a Unicode escape sequence. If you want to return a byte string containing the literal byte 0xA3, that's
return b'\xa3'
(where in Python 2 the b is implicit; but explicit is better than implicit).
The linked PEP in the error message instructs you exactly how to tell Python "this file is not pure ASCII; here's the encoding I'm using". If the encoding is UTF-8, that would be
# coding=utf-8
or the Emacs-compatible
# -*- encoding: utf-8 -*-
If you don't know which encoding your editor uses to save this file, examine it with something like a hex editor and some googling. The Stack Overflow character-encoding tag has a tag info page with more information and some troubleshooting tips.
In so many words, outside of the 7-bit ASCII range (0x00-0x7F), Python can't and mustn't guess what string a sequence of bytes represents. https://tripleee.github.io/8bit#a3 shows 21 possible interpretations for the byte 0xA3 and that's only from the legacy 8-bit encodings; but it could also very well be the first byte of a multi-byte encoding. But in fact, I would guess you are actually using Latin-1, so you should have
# coding: latin-1
as the first or second line of your source file. Anyway, without knowledge of which character the byte is supposed to represent, a human would not be able to guess this, either.
A caveat: coding: latin-1 will definitely remove the error message (because there are no byte sequences which are not technically permitted in this encoding), but might produce completely the wrong result when the code is interpreted if the actual encoding is something else. You really have to know the encoding of the file with complete certainty when you declare the encoding.
Adding the following two lines in the script solved the issue for me.
# !/usr/bin/python
# coding=utf-8
Hope it helps !
You're probably trying to run Python 3 file with Python 2 interpreter. Currently (as of 2019), python command defaults to Python 2 when both versions are installed, on Windows and most Linux distributions.
But in case you're indeed working on a Python 2 script, a not yet mentioned on this page solution is to resave the file in UTF-8+BOM encoding, that will add three special bytes to the start of the file, they will explicitly inform the Python interpreter (and your text editor) about the file encoding.
I have a python file that contains a long string of HTML. When I compile & run this file/script I get this error:
_SyntaxError: Non-ASCII character '\x92' in file C:\Users...\GlobalVars.py on line 2509, but no encoding declared; see http://www.python.org/peps/pep-0263.html for details_
I have followed the instructions and gone to the url suggested. But putting something like this at the top of my script still doesn't work:
#!/usr/bin/python
# -*- coding: latin-1 -*-
What do you think I can do to stop this compiler error from occuring?
First, in order to prevent problems like the one specified in the question you should not ever use other encoding than utf-8 for python source code.
This is the correct header to use
#! /usr/bin/env python
# -*- coding: utf-8 -*-
Now you have to convert the file from whatever encoding you may have to utf-8, probably your current text editor is able to do that.
If you wonder why I say this remember that it is impossible for a text editor to safely guess your non-unicode encoding because there is no BOM for non-unicode. For this reason most decent editors are using UTF-8 as default even when encoding is not specified. And BTW, the encoding specified in the python file header is for Python only, most editors ignore what you wrote there.
Also, as you can see Python is trying to decode a character above 128 using ASCII (not latin-1), this is supposed to fail. I am not sure why this happens but I don't even care too much because there is a much better way to solve the problem.
It must be at the top of the script that has the non-ASCII text, and it must match the actual encoding of the file. \x92 is CP1252, not Latin-1.
If you are just concerned about getting rid of this error without getting into the details of it(which you can get from the other answers on this page), you can do the following -
1) Copy your code and paste it in Notepad++
2) Select Encoding -> Encode in UTF-8
3) Select View -> Show Symbol -> Show All Characters
Now it would be visible to you that which symbol is causing the issue(x92 would be visible). Replace/Remove it to solve the problem.
Found this and hope it's helpful to the next person:
http://www.sitepoint.com/forums/showthread.php?567734-Anyone-know-what-this-error-means
Code point 0x92 (146 decimal) is the right single quotation mark, or
apostrophe (’) in Windows-1252. It's an invalid character in ISO 8859
and in UTF-8, since the 0x80-0x9F range is reserved for C1 control
characters.
Not sure if I'm busting copyright. If so please remove the blockquote.
The encoding declaration indicates that you think the file is in latin-1 encoding, but the python interpreter is finding that a char at or very near line 2509 in GlobalVars.py that is not what you think it is.
You should first confirm the encoding of GlobalVars.py. Is it really latin-1?
Next, you should check the characters near line 2509. Are they also latin-1, or were they cut and pasted from a web page or somewhere else (maybe there are UTF-8 chars mixed up in there)?
If you have chars in your source file that aren't what you think they are, then you may need to clean up the file before going any further.
add these lines on top of your code
#! /usr/bin/env python
# -*- coding: utf-8 -*-
An easy workaround solution if your file is really in latin-1 is to change the html string with its representation.
Afaik:
\x92 => 146 in decimal => Æ => Æ
If your character is not Æ, then your file is not encoded into latin-1 ;-) (and you might wanna check if utf-8/cp1292 works better as a quick win)
EDIT:
Of course, you want to check your ACTUAL file encoding before trying. I might be wrong, not 100% sure \x92 is Æ in Iso8859-1 : according to this page, it doesn't seem defined.