Python 2.7 build on Sublime Text 3 doesn't print the '\uFFFD' character

问题

The problem.

I'm using Python 2.7 build on Sublime Text 3 and have an issue with printing out.
In some cases I get a pretty confusing output for '\uFFFD' - the 'REPLACEMENT CHARACTER'.

---

For example:

print u'\ufffd' # should be '�' - the 'REPLACEMENT CHARACTER'
print u'\u0061' # should be 'a'
-----------------------------------------------------
[Finished in 0.1s]

After inversion of the order:

print u'\u0061' 
print u'\ufffd'
-----------------------------------------------------
a
�
[Finished in 0.1s]

So, Sublime can printout the '�' character, but for some reason doesn't do it in the 1st case.
And the dependence of the output on the order of statements seems quite strange.

---

The problem with replacement char leads to very unpredictable printout behavior in general.
For example, I want to printout decoded bytes with error replacement:

cp1251_bytes = '\xe4\xe0' # 'да' in cp1251 
print cp1251_bytes.decode('utf-8', errors='replace')
-----------------------------------------------------
��
[Finished in 0.1s]

Let's replace the bytes:

cp1251_bytes = '\xed\xe5\xf2' # 'нет' in cp1251
print cp1251_bytes.decode('utf-8', errors='replace')
-----------------------------------------------------
[Finished in 0.1s]

And add one more print statement:

cp1251_bytes = '\xed\xe5\xf2' # 'нет' in cp1251 
print cp1251_bytes.decode('cp1251') 
print cp1251_bytes.decode('utf-8', errors='replace')
-----------------------------------------------------
нет
���
[Finished in 0.1s]

---

Below is the illustration of implementation some other test cases:

---

Summarizing, there are the following patterns in the described printout behavior:

it depends on the even/odd number of '\ufffd' chars in print statement

it depends on the order of print statements

it depends on the specific build run

---

My questions:

Why does this happen?

How to fix the problem?

---

My Python 2.7 sublime-build file:

{   
    "cmd": ["C:\\_Anaconda3\\envs\\python27\\python", "-u", "$file"],
    "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)",
    "selector": "source.python",
    "env": {"PYTHONIOENCODING": "utf-8"}
}

With Python 2.7 installed separately from Anaconda the behavior is exactly the same.

回答1:

I've reproduced your problem and I've found a solution that works on my platform anyhow: Remove the -u flag from your cmd build config option.

I'm not 100% sure why that works, but it seems to be a poor interaction resulting from the console interpreting an unbuffered stream of data containing multi-byte characters. Here's what I've found:

• The -u option switches Python's output to unbuffered
• This problem is not at all specific to the replacement character. I've gotten similar behaviour with other characters like "あ" (U+3042).
• Similar bad results happen with other encodings. Setting "env": {"PYTHONIOENCODING": "utf-16be"} results in print u'\u3042' outputting 0B.

That last example with the encoding set to UTF-16BE illustrates what I think is going on. The console is receiving one byte at a time because the output is unbuffered. So it receives the 0x30 byte first. The console then determines this is not valid UTF-16BE and decides instead to fallback to ASCII and thus outputs 0. It of courses receives the next byte right after and follows the same logic to output B.

With the UTF-8 encoding, the console receives bytes that can't possibly be interpreted as ASCII, so I believe the console is doing a slightly better job at properly interpreting the unbuffered stream, but it is still running into the difficulties that your question points out.

回答2:

Edit-1 - Using UTF8 with BOM

Seems like BOM becomes important in case of windows. So you need to use below type build config

{   
    "cmd": ["F:\\Python27-14\\python", "-u", "$file"],
    "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)",
    "selector": "source.python",
    "env": {
        "PYTHONIOENCODING": "utf_8_sig"
    },
}

After that it works correctly for me on windows also

Original Answer

I checked the issue and I didn't face the same on Python 2.7 with Sublime text. The only change being I had to add # -*- coding: utf-8 -*- to the top of the file. Which seems the missing part in this question

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

print u'\u0061' # should be 'a'
print u'\ufffd' # should be '�' - the 'REPLACEMENT CHARACTER'

After that the reversal has no impact

You can see more details about this required header on

Why declare unicode by string in python?

Below is summary of the above link

When you specify # -*- coding: utf-8 -*-, you're telling Python the source file you've saved is utf-8. The default for Python 2 is ASCII (for Python 3 it's utf-8). This just affects how the interpreter reads the characters in the file.

来源：https://stackoverflow.com/questions/46856584/python-2-7-build-on-sublime-text-3-doesnt-print-the-ufffd-character