I have recently learned more in depth about ASCII, Unicode, UTF-8, UTF-16, etc. in Python3, but I am struggling to understand when would one run into issues while reading/writing to files.
So if I open a file:
with open(myfile, 'a') as f:
f.write(stuff)
where stuff = 'Hello World!'
I have no issues writing to a file.
If I have something like:
non_latin = '娜', I can still write to the file with no problems.
So when does one run into issues regarding encodings? When does one use encode() and decode()?
You run into issues if the default encoding for your OS doesn't support the characters written. In your case the default (obtained from locale.getpreferredencoding(False)) is probably UTF-8. On Windows, the default is an ANSI encoding like cp1252 and wouldn't support Chinese. Best to be explicit and use open(myfile,'w',encoding='utf8') for example.
Related
I have been reading quite some posts including this one
Javascript export CSV encoding utf-8 issue
I know lots mentioned it's because of microsoft excel that using something like this should work
https://superuser.com/questions/280603/how-to-set-character-encoding-when-opening-excel
I have tried on ubuntu (which didn't even have any issue), on windows10, which I have to use the second posts to import, on mac which has the biggest problem because mac does not import, does not read the unicode at all.
Is there anyway I can do it in coding while exporting to enforce excel to open with utf-8? or some other workaround I might be able to try?
Thanks in advance for any help and suggestions.
Many Windows applications, including Excel, assume the localized ANSI encoding (Windows-1252 on US Windows) when opening a file, unless the file starts with byte-order-mark (BOM) code point. While UTF-8 doesn't need a BOM, a UTF-8-encoded BOM at the start of a file clues Excel that the file is UTF-8. The byte sequence is EF BB BF and the equivalent Unicode code point is U+FEFF.
I'm trying to read in XLSX files with PHP. Using gneustaetter/XLSXReader to be exact. However, these XLSX-files are generated by different companies, using different software. So I wanted to check if they have the right encoding and always just found UTF-8.
Therefore my question as above:
Are XLSX files UTF-8 encoded by definition? Or are there exceptions that could break the import script I'm working on?
It'd be risky to presume it's always UTF-8. I'd just key your expectations to what the XML describes in the XML header. In my experience Windows-1252 encoded data shows up all the time when you least expect it. You might check the XLSX specification more closely to find out more.
Here's a Chromium bug relating to a Windows-1252 encoded XLSX file, so these seem to exist in the wild. Maybe they're produced by programs other than Microsoft Office. With things like LibreOffice becoming more popular, older versions that may not have had the most robust XLSX support might end up interacting with your code. You probably don't want to have a bug like this show up in your code.
Try and be as accommodating as possible unless you have a concrete reason for rejecting invalid encoding. JSON, by strict definition, is UTF-8. XLSX seems to be XML by definition, but the encoding is not as nailed down. UTF-8 simply seems to be the default convention.
For a class of mine I have to make a very basic calculator. I want to write the code in such a way that the user can just enter what they want to do (ex. √64) press return and get the answer. I wrote this:
if '√' in operation:
squareRoot = operation.replace('√','')
squareRootFinal = math.sqrt(int(squareRoot))
When I run this in IDLE, it works like a charm. However when I run this in Terminal I get the following error:
SyntaxError: Non-ASCII character '\xe2' in file x.py on line 50, but no encoding declared;
any suggestions?
Just declare the encoding. Python is begin a bit cautious here and not guessing the encoding of your text file. IDLE is a text editor and so has already guessed the encoding and stored things internally as unicode, which it can pass directly to the Python interpreter.
Put
#!/usr/bin/env python3
# -*- coding: UTF-8 -*-
at the top of the file. (It's pretty unlikely nowadays that your encoding is not UTF-8.)
For reference, in past times files had a variety of different possible encodings. That means that the same text could be stored in different ways in binary, when written to disk. Almost all encodings have the same interpretation of bytes 0 to 127—the ASCII subset. But if any other bytes occur in the file, their meaning is potentially ambiguous.
However, in recent years, UTF-8 has become by far the most common encoding, so it's almost always a safe guess.
I'm trying to write a object to a gzipped json file in one step (minimising code, and possibly saving memory space). My initial idea (python3) was thus:
import gzip, json
with gzip.open("/tmp/test.gz", mode="wb") as f:
json.dump({"a": 1}, f)
This however fails: TypeError: 'str' does not support the buffer interface, which I think has to do with a string not being encoded to bytes. So what is the proper way to do this?
Current solution that I'm unhappy with:
Opening the file in text-mode solves the problem:
import gzip, json
with gzip.open("/tmp/test.gz", mode="wt") as f:
json.dump({"a": 1}, f)
however I don't like text-mode. In my mind (and maybe this is wrong, but supported by this), text mode is used to fix line-endings. This shouldn't be an issue because json doesn't have line endings, but I don't like it (possibly) messing with my bytes, it (possibly) is slower because it's looking for line-endings to fix, and (worst of all) I don't understand why something about line-endings fixes my encoding problems?
offtopic: I should have dived into the docs a bit further than I initially did.
The python docs show:
Normally, files are opened in text mode, that means, you read and write strings from and to the file, which are encoded in a specific encoding (the default being UTF-8). 'b' appended to the mode opens the file in binary mode: now the data is read and written in the form of bytes objects. This mode should be used for all files that don’t contain text.
I don't fully agree that the result from a json encode is a string (I think it should be a set of bytes, since it explicitly defines that it uses utf-8 encoding), but I noticed this before. So I guess text mode it is.
I have a CSV file with special accents and save it in Notepad by selecting UTF-8 encoding. When I read the file using Java, it reads the BOM characters too.
So I want to save this file in UTF-8 format without appending a BOM initially in Notepad.
Otherwise, is there a built-in class in Java that eliminates the BOM characters that present at beginning, when reading the contents in a file?
Use Notepad++ - it is free and much better than Notepad. It will help to save text without a BOM using Encoding → Encode in UTF-8 without BOM: Notepad++ v6 and olders:
Notepad++ v7+:
When I encountered this problem in Java, I didn't find any library to parse these first three bytes (BOM). So my advice:
Use PushbackInputStream(in, 3).
Read the first three bytes
If it's not BOM (EF BB BF), push them back
Process the stream as UTF-8
I just learned from this Stack Overflow post, as #martin-geisler points out, that you can save files without the BOM in Windows Notepad, by selecting ANSI as the encoding.
I'm assuming that for more advanced uses this won't work because the resulting file is probably not the end encoding wished, but actually ANSI; but I tested and confirmed this works to save a very small .php script without BOM using only Notepad.
I learned the long, hard way that Windows' Notepad is not a true editor, although I'd like to point out for others that, despite this, it is misleadingly called up when you type "editor" on newer Windows machines, at least on one of mine.
I am currently using Emacs and other editors to solve this problem.
Use Notepad++ instead. See my personal blog post on it. From within Notepad++, choose the "Encoding" menu, then "Encode in UTF-8 without BOM".
Notepad on Windows 10 version 1903 (May 2019 update) and later versions supports saving to UTF-8 without a BOM. In fact, UTF-8 is the default file format now.
Reference: Windows 10 Notepad is Getting Better UTF-8 Encoding Support
The answer is: Not at all. Notepad can't do that.
In Java you can just skip the first byte in your InputStream and be done.
You might want to try out Notepad2 or Notepad++. Those Notepad replacements have the option for you to choose whether to output BOM.
As for a Java solution, as far as I know, Java does not understand the standard UTF-8. I googled and found Java's UTF-8 and Unicode writing is broken - Use this fix that might be the solution.
We're using the utility BOMStripperInputStream.java to strip the BOM from our input if present.