Base64 encoding issue in Python - python

I need to save a params file in python and this params file contains some parameters that I won't leave on plain text, so I codify the entire file to base64 (I know that this isn't the most secure encoding of the world but it works for the kind of data that I need to use).
With the encoding, everything works well. I encode the content of my file (a simply txt with a proper extension) and save the file. The problem comes with the decode. I print the text coded before save the file and the text coded from the file saved and there are exactly the same, but for a reason I don't know, the decode of the text of the file saved returns me this error UnicodeDecodeError: 'utf-8' codec can't decode byte 0x8d in position 1: invalid start byte and the decode of the text before save the file works well.
Any idea to resolve this issue?
This is my code, I have tried converting all to bytes, to string, and everything...
params = open('params.bpr','r').read()
paramsencoded = base64.b64encode(bytes(params,'utf-8'))
print(paramsencoded)
paramsdecoded = str(base64.b64decode(str(paramsencoded,'utf-8')),'utf-8')
newparams = open('paramsencoded.bpr','w+',encoding='utf-8')
newparams.write(str(paramsencoded))
newparams.close()
params2 = open('paramsencoded.bpr',encoding='utf-8').read()
print(params2)
paramsdecoded = str(base64.b64decode(str(paramsencoded,'utf-8')),'utf-8')
paramsdecoded = base64.b64decode(str(params2))
print(str(paramsdecoded,'utf-8'))

Your error lies in your handling of the bytes object returned by base64.b64encode(), you called str() on the object:
newparams.write(str(paramsencoded))
That doesn't decode the bytes object:
>>> bytesvalue = b'abc='
>>> str(bytesvalue)
"b'abc='"
Note the b'...' notation. You produced the representation of the bytes object, which is a string containing Python syntax that can reproduce the value for debugging purposes (you can copy that string value and paste it into Python to re-create the same bytes value).
This may not be that easy to notice at first, as base64.b64encode() otherwise only produces output with printable ASCII bytes.
But your decoding problem originates from there, because when decoding the value read back from the file includes the b' characters at the start. Those first two characters are interpreted as Base64 data too; the b is a valid Base64 character, and the ' is ignored by the parser:
>>> bytesvalue = b'hello world'
>>> base64.b64encode(bytesvalue)
b'aGVsbG8gd29ybGQ='
>>> str(base64.b64encode(bytesvalue))
"b'aGVsbG8gd29ybGQ='"
>>> base64.b64decode(str(base64.b64encode(bytesvalue))) # with str()
b'm\xa1\x95\xb1\xb1\xbc\x81\xdd\xbd\xc9\xb1\x90'
>>> base64.b64decode(base64.b64encode(bytesvalue)) # without str()
b'hello world'
Note how the output is completely different, because the Base64 decoding is now starting from the wrong place, as b is the first 6 bits of the first byte (making the first decoded byte a 6C, 6D, 6E or 6F bytes, so m,n, o or p ASCII).
You could properly decode the value (using paramsencoded.decode('ascii') or str(paramsencoded, 'ascii')) but you should't treat any of this data as text.
Instead, open your files in binary mode. Reading and writing then operates with bytes objects, and the base64.b64encode() and base64.b64decode() functions also operate on bytes, making for a perfect match:
with open('params.bpr', 'rb') as params_source:
params = params_source.read() # bytes object
params_encoded = base64.b64encode(params)
print(params_encoded.decode('ascii')) # base64 data is always ASCII data
params_decoded = base64.b64decode(params_encoded)
with open('paramsencoded.bpr', 'wb') as new_params:
newparams.write(params_encoded) # write binary data
with open('paramsencoded.bpr', 'rb') as new_params:
params_written = new_params.read()
print(params_written.decode('ascii')) # still Base64 data, so decode as ASCII
params_decoded = base64.b64decode(params_written) # decode the bytes value
print(params_decoded.decode('utf8')) # assuming the original source was UTF-8
I explicitly use bytes.decode(codec) rather than str(..., codec) to avoid accidental str(...) calls.

Related

Reading bytes from file python And converting to String

I have a file including some data like : \xe1\x8a\xa0\xe1\x88\x9b\xe1\x88\xad\xe1\x8a\x9b
How do i read this and write the string format(አማርኛ) in another file? And also vice versa?
[\xe1\x8a\xa0\xe1\x88\x9b\xe1\x88\xad\xe1\x8a\x9b == አማርኛ ]
That is a byte string, so you need to decode it to a utf-8 Unicode string.
b'\xe1\x8a\xa0\xe1\x88\x9b\xe1\x88\xad\xe1\x8a\x9b'.decode('utf8')
result: 'አማርኛ'
And to encode it back to byte string:
'አማርኛ'.encode()
result: b'\xe1\x8a\xa0\xe1\x88\x9b\xe1\x88\xad\xe1\x8a\x9b'
Basicly you have a byte string, you can do what you are talking about with the functions encode() and decode() respectively, in the example below, i will start by printing the byte string. And then i'm taking the byte string and decoding it to utf-8 (default value in all python versions above 2.7 if you don't specify a version yourself)
f = open("input.txt","rb")
x = f.read()
print(x) # b'\xe1\x8a\xa0\xe1\x88\x9b\xe1\x88\xad\xe1\x8a\x9b'
print(x.decode()) # አማርኛ
If you want to do the inverse operation, you can achieve this by just encoding back the decoded byte array! (Do note that the open function i'm using the arguments "rb" that stands for (following the wiki) "Opens a file for reading only in binary format."

Getting decoding error from server database [duplicate]

as3:~/ngokevin-site# nano content/blog/20140114_test-chinese.mkd
as3:~/ngokevin-site# wok
Traceback (most recent call last):
File "/usr/local/bin/wok", line 4, in
Engine()
File "/usr/local/lib/python2.7/site-packages/wok/engine.py", line 104, in init
self.load_pages()
File "/usr/local/lib/python2.7/site-packages/wok/engine.py", line 238, in load_pages
p = Page.from_file(os.path.join(root, f), self.options, self, renderer)
File "/usr/local/lib/python2.7/site-packages/wok/page.py", line 111, in from_file
page.meta['content'] = page.renderer.render(page.original)
File "/usr/local/lib/python2.7/site-packages/wok/renderers.py", line 46, in render
return markdown(plain, Markdown.plugins)
File "/usr/local/lib/python2.7/site-packages/markdown/init.py", line 419, in markdown
return md.convert(text)
File "/usr/local/lib/python2.7/site-packages/markdown/init.py", line 281, in convert
source = unicode(source)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe8 in position 1: ordinal not in range(128). -- Note: Markdown only accepts unicode input!
How to fix it?
In some other python-based static blog apps, Chinese post can be published successfully.
Such as this app: http://github.com/vrypan/bucket3. In my site http://bc3.brite.biz/, Chinese post can be published successfully.
tl;dr / quick fix
Don't decode/encode willy nilly
Don't assume your strings are UTF-8 encoded
Try to convert strings to Unicode strings as soon as possible in your code
Fix your locale: How to solve UnicodeDecodeError in Python 3.6?
Don't be tempted to use quick reload hacks
Unicode Zen in Python 2.x - The Long Version
Without seeing the source it's difficult to know the root cause, so I'll have to speak generally.
UnicodeDecodeError: 'ascii' codec can't decode byte generally happens when you try to convert a Python 2.x str that contains non-ASCII to a Unicode string without specifying the encoding of the original string.
In brief, Unicode strings are an entirely separate type of Python string that does not contain any encoding. They only hold Unicode point codes and therefore can hold any Unicode point from across the entire spectrum. Strings contain encoded text, beit UTF-8, UTF-16, ISO-8895-1, GBK, Big5 etc. Strings are decoded to Unicode and Unicodes are encoded to strings. Files and text data are always transferred in encoded strings.
The Markdown module authors probably use unicode() (where the exception is thrown) as a quality gate to the rest of the code - it will convert ASCII or re-wrap existing Unicodes strings to a new Unicode string. The Markdown authors can't know the encoding of the incoming string so will rely on you to decode strings to Unicode strings before passing to Markdown.
Unicode strings can be declared in your code using the u prefix to strings. E.g.
>>> my_u = u'my ünicôdé strįng'
>>> type(my_u)
<type 'unicode'>
Unicode strings may also come from file, databases and network modules. When this happens, you don't need to worry about the encoding.
Gotchas
Conversion from str to Unicode can happen even when you don't explicitly call unicode().
The following scenarios cause UnicodeDecodeError exceptions:
# Explicit conversion without encoding
unicode('€')
# New style format string into Unicode string
# Python will try to convert value string to Unicode first
u"The currency is: {}".format('€')
# Old style format string into Unicode string
# Python will try to convert value string to Unicode first
u'The currency is: %s' % '€'
# Append string to Unicode
# Python will try to convert string to Unicode first
u'The currency is: ' + '€'
Examples
In the following diagram, you can see how the word café has been encoded in either "UTF-8" or "Cp1252" encoding depending on the terminal type. In both examples, caf is just regular ascii. In UTF-8, é is encoded using two bytes. In "Cp1252", é is 0xE9 (which is also happens to be the Unicode point value (it's no coincidence)). The correct decode() is invoked and conversion to a Python Unicode is successfull:
In this diagram, decode() is called with ascii (which is the same as calling unicode() without an encoding given). As ASCII can't contain bytes greater than 0x7F, this will throw a UnicodeDecodeError exception:
The Unicode Sandwich
It's good practice to form a Unicode sandwich in your code, where you decode all incoming data to Unicode strings, work with Unicodes, then encode to strs on the way out. This saves you from worrying about the encoding of strings in the middle of your code.
Input / Decode
Source code
If you need to bake non-ASCII into your source code, just create Unicode strings by prefixing the string with a u. E.g.
u'Zürich'
To allow Python to decode your source code, you will need to add an encoding header to match the actual encoding of your file. For example, if your file was encoded as 'UTF-8', you would use:
# encoding: utf-8
This is only necessary when you have non-ASCII in your source code.
Files
Usually non-ASCII data is received from a file. The io module provides a TextWrapper that decodes your file on the fly, using a given encoding. You must use the correct encoding for the file - it can't be easily guessed. For example, for a UTF-8 file:
import io
with io.open("my_utf8_file.txt", "r", encoding="utf-8") as my_file:
my_unicode_string = my_file.read()
my_unicode_string would then be suitable for passing to Markdown. If a UnicodeDecodeError from the read() line, then you've probably used the wrong encoding value.
CSV Files
The Python 2.7 CSV module does not support non-ASCII characters 😩. Help is at hand, however, with https://pypi.python.org/pypi/backports.csv.
Use it like above but pass the opened file to it:
from backports import csv
import io
with io.open("my_utf8_file.txt", "r", encoding="utf-8") as my_file:
for row in csv.reader(my_file):
yield row
Databases
Most Python database drivers can return data in Unicode, but usually require a little configuration. Always use Unicode strings for SQL queries.
MySQL
In the connection string add:
charset='utf8',
use_unicode=True
E.g.
>>> db = MySQLdb.connect(host="localhost", user='root', passwd='passwd', db='sandbox', use_unicode=True, charset="utf8")
PostgreSQL
Add:
psycopg2.extensions.register_type(psycopg2.extensions.UNICODE)
psycopg2.extensions.register_type(psycopg2.extensions.UNICODEARRAY)
HTTP
Web pages can be encoded in just about any encoding. The Content-type header should contain a charset field to hint at the encoding. The content can then be decoded manually against this value. Alternatively, Python-Requests returns Unicodes in response.text.
Manually
If you must decode strings manually, you can simply do my_string.decode(encoding), where encoding is the appropriate encoding. Python 2.x supported codecs are given here: Standard Encodings. Again, if you get UnicodeDecodeError then you've probably got the wrong encoding.
The meat of the sandwich
Work with Unicodes as you would normal strs.
Output
stdout / printing
print writes through the stdout stream. Python tries to configure an encoder on stdout so that Unicodes are encoded to the console's encoding. For example, if a Linux shell's locale is en_GB.UTF-8, the output will be encoded to UTF-8. On Windows, you will be limited to an 8bit code page.
An incorrectly configured console, such as corrupt locale, can lead to unexpected print errors. PYTHONIOENCODING environment variable can force the encoding for stdout.
Files
Just like input, io.open can be used to transparently convert Unicodes to encoded byte strings.
Database
The same configuration for reading will allow Unicodes to be written directly.
Python 3
Python 3 is no more Unicode capable than Python 2.x is, however it is slightly less confused on the topic. E.g the regular str is now a Unicode string and the old str is now bytes.
The default encoding is UTF-8, so if you .decode() a byte string without giving an encoding, Python 3 uses UTF-8 encoding. This probably fixes 50% of people's Unicode problems.
Further, open() operates in text mode by default, so returns decoded str (Unicode ones). The encoding is derived from your locale, which tends to be UTF-8 on Un*x systems or an 8-bit code page, such as windows-1251, on Windows boxes.
Why you shouldn't use sys.setdefaultencoding('utf8')
It's a nasty hack (there's a reason you have to use reload) that will only mask problems and hinder your migration to Python 3.x. Understand the problem, fix the root cause and enjoy Unicode zen.
See Why should we NOT use sys.setdefaultencoding("utf-8") in a py script? for further details
Finally I got it:
as3:/usr/local/lib/python2.7/site-packages# cat sitecustomize.py
# encoding=utf8
import sys
reload(sys)
sys.setdefaultencoding('utf8')
Let me check:
as3:~/ngokevin-site# python
Python 2.7.6 (default, Dec 6 2013, 14:49:02)
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> reload(sys)
<module 'sys' (built-in)>
>>> sys.getdefaultencoding()
'utf8'
>>>
The above shows the default encoding of python is utf8. Then the error is no more.
This is the classic "unicode issue". I believe that explaining this is beyond the scope of a StackOverflow answer to completely explain what is happening.
It is well explained here.
In very brief summary, you have passed something that is being interpreted as a string of bytes to something that needs to decode it into Unicode characters, but the default codec (ascii) is failing.
The presentation I pointed you to provides advice for avoiding this. Make your code a "unicode sandwich". In Python 2, the use of from __future__ import unicode_literals helps.
Update: how can the code be fixed:
OK - in your variable "source" you have some bytes. It is not clear from your question how they got in there - maybe you read them from a web form? In any case, they are not encoded with ascii, but python is trying to convert them to unicode assuming that they are. You need to explicitly tell it what the encoding is. This means that you need to know what the encoding is! That is not always easy, and it depends entirely on where this string came from. You could experiment with some common encodings - for example UTF-8. You tell unicode() the encoding as a second parameter:
source = unicode(source, 'utf-8')
In some cases, when you check your default encoding (print sys.getdefaultencoding()), it returns that you are using ASCII. If you change to UTF-8, it doesn't work, depending on the content of your variable.
I found another way:
import sys
reload(sys)
sys.setdefaultencoding('Cp1252')
I was searching to solve the following error message:
unicodedecodeerror: 'ascii' codec can't decode byte 0xe2 in position 5454: ordinal not in range(128)
I finally got it fixed by specifying 'encoding':
f = open('../glove/glove.6B.100d.txt', encoding="utf-8")
Wish it could help you too.
"UnicodeDecodeError: 'ascii' codec can't decode byte"
Cause of this error: input_string must be unicode but str was given
"TypeError: Decoding Unicode is not supported"
Cause of this error: trying to convert unicode input_string into unicode
So first check that your input_string is str and convert to unicode if necessary:
if isinstance(input_string, str):
input_string = unicode(input_string, 'utf-8')
Secondly, the above just changes the type but does not remove non ascii characters. If you want to remove non-ascii characters:
if isinstance(input_string, str):
input_string = input_string.decode('ascii', 'ignore').encode('ascii') #note: this removes the character and encodes back to string.
elif isinstance(input_string, unicode):
input_string = input_string.encode('ascii', 'ignore')
In order to resolve this on an operating system level in an Ubuntu installation check the following:
$ locale charmap
If you get
locale: Cannot set LC_CTYPE to default locale: No such file or directory
instead of
UTF-8
then set LC_CTYPE and LC_ALL like this:
$ export LC_ALL="en_US.UTF-8"
$ export LC_CTYPE="en_US.UTF-8"
I find the best is to always convert to unicode - but this is difficult to achieve because in practice you'd have to check and convert every argument to every function and method you ever write that includes some form of string processing.
So I came up with the following approach to either guarantee unicodes or byte strings, from either input. In short, include and use the following lambdas:
# guarantee unicode string
_u = lambda t: t.decode('UTF-8', 'replace') if isinstance(t, str) else t
_uu = lambda *tt: tuple(_u(t) for t in tt)
# guarantee byte string in UTF8 encoding
_u8 = lambda t: t.encode('UTF-8', 'replace') if isinstance(t, unicode) else t
_uu8 = lambda *tt: tuple(_u8(t) for t in tt)
Examples:
text='Some string with codes > 127, like Zürich'
utext=u'Some string with codes > 127, like Zürich'
print "==> with _u, _uu"
print _u(text), type(_u(text))
print _u(utext), type(_u(utext))
print _uu(text, utext), type(_uu(text, utext))
print "==> with u8, uu8"
print _u8(text), type(_u8(text))
print _u8(utext), type(_u8(utext))
print _uu8(text, utext), type(_uu8(text, utext))
# with % formatting, always use _u() and _uu()
print "Some unknown input %s" % _u(text)
print "Multiple inputs %s, %s" % _uu(text, text)
# but with string.format be sure to always work with unicode strings
print u"Also works with formats: {}".format(_u(text))
print u"Also works with formats: {},{}".format(*_uu(text, text))
# ... or use _u8 and _uu8, because string.format expects byte strings
print "Also works with formats: {}".format(_u8(text))
print "Also works with formats: {},{}".format(*_uu8(text, text))
Here's some more reasoning about this.
Got a same error and this solved my error. Thanks!
python 2 and python 3 differing in unicode handling is making pickled files quite incompatible to load. So Use python pickle's encoding argument. Link below helped me solve the similar problem when I was trying to open pickled data from my python 3.7, while my file was saved originally in python 2.x version.
https://blog.modest-destiny.com/posts/python-2-and-3-compatible-pickle-save-and-load/
I copy the load_pickle function in my script and called the load_pickle(pickle_file) while loading my input_data like this:
input_data = load_pickle("my_dataset.pkl")
The load_pickle function is here:
def load_pickle(pickle_file):
try:
with open(pickle_file, 'rb') as f:
pickle_data = pickle.load(f)
except UnicodeDecodeError as e:
with open(pickle_file, 'rb') as f:
pickle_data = pickle.load(f, encoding='latin1')
except Exception as e:
print('Unable to load data ', pickle_file, ':', e)
raise
return pickle_data
Encode converts a unicode object in to a string object. I think you are trying to encode a string object. first convert your result into unicode object and then encode that unicode object into 'utf-8'.
for example
result = yourFunction()
result.decode().encode('utf-8')
This worked for me:
file = open('docs/my_messy_doc.pdf', 'rb')
I had the same error, with URLs containing non-ascii chars (bytes with values > 128), my solution:
url = url.decode('utf8').encode('utf-8')
Note: utf-8, utf8 are simply aliases . Using only 'utf8' or 'utf-8' should work in the same way
In my case, worked for me, in Python 2.7, I suppose this assignment changed 'something' in the str internal representation--i.e., it forces the right decoding of the backed byte sequence in url and finally puts the string into a utf-8 str with all the magic in the right place.
Unicode in Python is black magic for me.
Hope useful
I had the same problem but it didn't work for Python 3. I followed this and it solved my problem:
enc = sys.getdefaultencoding()
file = open(menu, "r", encoding = enc)
You have to set the encoding when you are reading/writing the file.
I got the same problem with the string "Pastelería Mallorca" and I solved with:
unicode("Pastelería Mallorca", 'latin-1')
In short, to ensure proper unicode handling in Python 2:
use io.open for reading/writing files
use from __future__ import unicode_literals
configure other data inputs/outputs (e.g., databases, network) to use unicode
if you cannot configure outputs to utf-8, convert your output for them print(text.encode('ascii', 'replace').decode())
For explanations, see #Alastair McCormack's detailed answer.
In a Django (1.9.10)/Python 2.7.5 project I have frequent UnicodeDecodeError exceptions; mainly when I try to feed unicode strings to logging. I made a helper function for arbitrary objects to basically format to 8-bit ascii strings and replacing any characters not in the table to '?'. I think it's not the best solution but since the default encoding is ascii (and i don't want to change it) it will do:
def encode_for_logging(c, encoding='ascii'):
if isinstance(c, basestring):
return c.encode(encoding, 'replace')
elif isinstance(c, Iterable):
c_ = []
for v in c:
c_.append(encode_for_logging(v, encoding))
return c_
else:
return encode_for_logging(unicode(c))
`
This error occurs when there are some non ASCII characters in our string and we are performing any operations on that string without proper decoding.
This helped me solve my problem.
I am reading a CSV file with columns ID,Text and decoding characters in it as below:
train_df = pd.read_csv("Example.csv")
train_data = train_df.values
for i in train_data:
print("ID :" + i[0])
text = i[1].decode("utf-8",errors="ignore").strip().lower()
print("Text: " + text)
Here is my solution, just add the encoding.
with open(file, encoding='utf8') as f
And because reading glove file will take a long time, I recommend to the glove file to a numpy file. When netx time you read the embedding weights, it will save your time.
import numpy as np
from tqdm import tqdm
def load_glove(file):
"""Loads GloVe vectors in numpy array.
Args:
file (str): a path to a glove file.
Return:
dict: a dict of numpy arrays.
"""
embeddings_index = {}
with open(file, encoding='utf8') as f:
for i, line in tqdm(enumerate(f)):
values = line.split()
word = ''.join(values[:-300])
coefs = np.asarray(values[-300:], dtype='float32')
embeddings_index[word] = coefs
return embeddings_index
# EMBEDDING_PATH = '../embedding_weights/glove.840B.300d.txt'
EMBEDDING_PATH = 'glove.840B.300d.txt'
embeddings = load_glove(EMBEDDING_PATH)
np.save('glove_embeddings.npy', embeddings)
Gist link: https://gist.github.com/BrambleXu/634a844cdd3cd04bb2e3ba3c83aef227
Specify: # encoding= utf-8 at the top of your Python File, It should fix the issue
I experienced this error with Python2.7. It happened to me while trying to run many python programs, but I managed to reproduce it with this simple script:
#!/usr/bin/env python
import subprocess
import sys
result = subprocess.Popen([u'svn', u'info'])
if not callable(getattr(result, "__enter__", None)) and not callable(getattr(result, "__exit__", None)):
print("foo")
print("bar")
On success, it should print out 'foo' and 'bar', and probably an error message if you're not in a svn folder.
On failure, it should print 'UnicodeDecodeError: 'ascii' codec can't decode byte 0xc4 in position 39: ordinal not in range(128)'.
After trying to regenerate my locales and many other solutions posted in this question, I learned the error was happening because I had a special character (ĺ) encoded in my PATH environment variable. After fixing the PATH in '~/.bashrc', and exiting my session and entering again, (apparently sourcing '~/.bashrc' didn't work), the issue was gone.

Python 3 and base64 encoding of a binary file

I'm new to Python and I do have an issue that is bothering me.
I use the following code to get a base64 string representation of my zip file.
with open( "C:\\Users\\Mario\\Downloads\\exportTest1.zip",'rb' ) as file:
zipContents = file.read()
encodedZip = base64.encodestring(zipContents)
Now, if I output the string it is contained inside a b'' representation. This for me is not necessary and I would like to avoid it. Also it adds a newlines character every 76 characters which is another issue. Is there a way to get the binary content and represent it without the newline characters and trailing and leading b''?
Just for comparison, if I do the following in PowerShell:
$fileName = "C:\Users\Mario\Downloads\exportTest1.zip"
$fileContentBytes = [System.IO.File]::ReadAllBytes($fileName)
$fileContentEncoded = [System.Convert]::ToBase64String($fileContentBytes)
I do get the exact string I'm looking for, no b'' and no \n every 76 chars.
From the base64 package doc:
base64.encodestring:
"Encode the bytes-like object s, which can contain arbitrary binary data, and return bytes containing the base64-encoded data, with newlines (b"\n") inserted after every 76 bytes of output, and ensuring that there is a trailing newline, as per RFC 2045 (MIME)."
You want to use
base64.b64encode:
"Encode the bytes-like object s using Base64 and return the encoded bytes."
Example:
import base64
with open("test.zip", "rb") as f:
encodedZip = base64.b64encode(f.read())
print(encodedZip.decode())
The decode() will convert the binary string to text.
Use b64encode to encode without the newlines and then decode the resulting binary string with .decode('ascii') to get a normal string.
encodedZip = base64.b64encode(zipContents).decode('ascii')

Python bytearray ignoring encoding?

I've got a chunk of code that reads binary data off a string buffer (StringIO object), and tries to convert it to a bytearray object, but it's throwing errors when the value is greater than 127, which the ascii encoding can't handle, even when I'm trying to override it:
file = open(filename, 'r+b')
file.seek(offset)
chunk = file.read(length)
chunk = zlib.decompress(chunk)
chunk = StringIO(chunk)
d = bytearray(chunk.read(10), encoding="iso8859-1", errors="replace")
Running that code gives me:
d = bytearray(chunk.read(10), encoding="iso8859-1", errors="replace")
UnicodeDecodeError: 'ascii' codec can't decode byte 0xf0 in position 3: ordinal not in range(128)
Obviously 240 (decimal of 0xf0) can't fit in the ascii encoding range, but that's why I'm explicitly setting the encoding. But it seems to be ignoring it.
When converting a string to another encoding, its original encoding is taken to be ASCII if it is a str or Unicode if it is a unicode object. When creating the bytearray, the encoding parameter is required only if the string is unicode. Just don't specify an encoding and you will get the results you want.
I am not quite sure what the problem is.
StringIO is for string IO, not for binary IO.
If you want to get a bytearray representing the whole content of the file, use:
with open ('filename', 'r') as file: bytes = bytearray (file.read () )
if you want to get a string with only ascii characters contained in that file, use:
with open ('filename', 'r') as file: asciis = file.read ().decode ('ascii', 'ignore')
(If you run it on windows, you will probably need the binary flag for opening the file.

Converting from utf-16 to utf-8 in Python 3

I'm programming in Python 3 and I'm having a small problem which I can't find any reference to it on the net.
As far as I understand the default string in is utf-16, but I must work with utf-8, I can't find the command that will convert from the default one to utf-8.
I'd appreciate your help very much.
In Python 3 there are two different datatypes important when you are working with string manipulation. First there is the string class, an object that represents unicode code points. Important to get is that this string is not some bytes, but really a sequence of characters. Secondly, there is the bytes class, which is just a sequence of bytes, often representing an string stored in an encoding (like utf-8 or iso-8859-15).
What does this mean for you? As far as I understand you want to read and write utf-8 files. Let's make a program that replaces all 'ć' with 'ç' characters
def main():
# Let's first open an output file. See how we give an encoding to let python know, that when we print something to the file, it should be encoded as utf-8
with open('output_file', 'w', encoding='utf-8') as out_file:
# read every line. We give open() the encoding so it will return a Unicode string.
for line in open('input_file', encoding='utf-8'):
#Replace the characters we want. When you define a string in python it also is automatically a unicode string. No worries about encoding there. Because we opened the file with the utf-8 encoding, the print statement will encode the whole string to utf-8.
print(line.replace('ć', 'ç'), out_file)
So when should you use bytes? Not often. An example I could think of would be when you read something from a socket. If you have this in an bytes object, you could make it a unicode string by doing bytes.decode('encoding') and visa versa with str.encode('encoding'). But as said, probably you won't need it.
Still, because it is interesting, here the hard way, where you encode everything yourself:
def main():
# Open the file in binary mode. So we are going to write bytes to it instead of strings
with open('output_file', 'wb') as out_file:
# read every line. Again, we open it binary, so we get bytes
for line_bytes in open('input_file', 'rb'):
#Convert the bytes to a string
line_string = bytes.decode('utf-8')
#Replace the characters we want.
line_string = line_string.replace('ć', 'ç')
#Make a bytes to print
out_bytes = line_string.encode('utf-8')
#Print the bytes
print(out_bytes, out_file)
Good reading about this topic (string encodings) is http://www.joelonsoftware.com/articles/Unicode.html. Really recommended read!
Source: http://docs.python.org/release/3.0.1/whatsnew/3.0.html#text-vs-data-instead-of-unicode-vs-8-bit
(P.S. As you see, I didn't mention utf-16 in this post. I actually don't know whether python uses this as internal decoding or not, but it is totally irrelevant. At the moment you are working with a string, you work with characters (code points), not bytes.

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