问题
I received some text that is encoded, but I don\'t know what charset was used. Is there a way to determine the encoding of a text file using Python? How can I detect the encoding/codepage of a text file deals with C#.
回答1:
Correctly detecting the encoding all times is impossible.
(From chardet FAQ:)
However, some encodings are optimized for specific languages, and languages are not random. Some character sequences pop up all the time, while other sequences make no sense. A person fluent in English who opens a newspaper and finds “txzqJv 2!dasd0a QqdKjvz” will instantly recognize that that isn't English (even though it is composed entirely of English letters). By studying lots of “typical” text, a computer algorithm can simulate this kind of fluency and make an educated guess about a text's language.
There is the chardet library that uses that study to try to detect encoding. chardet is a port of the auto-detection code in Mozilla.
You can also use UnicodeDammit. It will try the following methods:
- An encoding discovered in the document itself: for instance, in an XML declaration or (for HTML documents) an http-equiv META tag. If Beautiful Soup finds this kind of encoding within the document, it parses the document again from the beginning and gives the new encoding a try. The only exception is if you explicitly specified an encoding, and that encoding actually worked: then it will ignore any encoding it finds in the document.
- An encoding sniffed by looking at the first few bytes of the file. If an encoding is detected at this stage, it will be one of the UTF-* encodings, EBCDIC, or ASCII.
- An encoding sniffed by the chardet library, if you have it installed.
- UTF-8
- Windows-1252
回答2:
Another option for working out the encoding is to use libmagic (which is the code behind the file command). There are a profusion of python bindings available.
The python bindings that live in the file source tree are available as the python-magic (or python3-magic) debian package. It can determine the encoding of a file by doing:
import magic
blob = open('unknown-file').read()
m = magic.open(magic.MAGIC_MIME_ENCODING)
m.load()
encoding = m.buffer(blob) # "utf-8" "us-ascii" etc
There is an identically named, but incompatible, python-magic pip package on pypi that also uses libmagic. It can also get the encoding, by doing:
import magic
blob = open('unknown-file').read()
m = magic.Magic(mime_encoding=True)
encoding = m.from_buffer(blob)
回答3:
Some encoding strategies, please uncomment to taste :
#!/bin/bash
#
tmpfile=$1
echo '-- info about file file ........'
file -i $tmpfile
enca -g $tmpfile
echo 'recoding ........'
#iconv -f iso-8859-2 -t utf-8 back_test.xml > $tmpfile
#enca -x utf-8 $tmpfile
#enca -g $tmpfile
recode CP1250..UTF-8 $tmpfile
You might like to check the encoding by opening and reading the file in a form of a loop... but you might need to check the filesize first :
encodings = ['utf-8', 'windows-1250', 'windows-1252' ...etc]
for e in encodings:
try:
fh = codecs.open('file.txt', 'r', encoding=e)
fh.readlines()
fh.seek(0)
except UnicodeDecodeError:
print('got unicode error with %s , trying different encoding' % e)
else:
print('opening the file with encoding: %s ' % e)
break
回答4:
Here is an example of reading and taking at face value a chardet encoding prediction, reading n_lines from the file in the event it is large.
chardet also gives you a probability (i.e. confidence) of it's encoding prediction (haven't looked how they come up with that), which is returned with its prediction from chardet.predict(), so you could work that in somehow if you like.
def predict_encoding(file_path, n_lines=20):
'''Predict a file's encoding using chardet'''
import chardet
# Open the file as binary data
with open(file_path, 'rb') as f:
# Join binary lines for specified number of lines
rawdata = b''.join([f.readline() for _ in range(n_lines)])
return chardet.detect(rawdata)['encoding']
回答5:
# Function: OpenRead(file)
# A text file can be encoded using:
# (1) The default operating system code page, Or
# (2) utf8 with a BOM header
#
# If a text file is encoded with utf8, and does not have a BOM header,
# the user can manually add a BOM header to the text file
# using a text editor such as notepad++, and rerun the python script,
# otherwise the file is read as a codepage file with the
# invalid codepage characters removed
import sys
if int(sys.version[0]) != 3:
print('Aborted: Python 3.x required')
sys.exit(1)
def bomType(file):
"""
returns file encoding string for open() function
EXAMPLE:
bom = bomtype(file)
open(file, encoding=bom, errors='ignore')
"""
f = open(file, 'rb')
b = f.read(4)
f.close()
if (b[0:3] == b'\xef\xbb\xbf'):
return "utf8"
# Python automatically detects endianess if utf-16 bom is present
# write endianess generally determined by endianess of CPU
if ((b[0:2] == b'\xfe\xff') or (b[0:2] == b'\xff\xfe')):
return "utf16"
if ((b[0:5] == b'\xfe\xff\x00\x00')
or (b[0:5] == b'\x00\x00\xff\xfe')):
return "utf32"
# If BOM is not provided, then assume its the codepage
# used by your operating system
return "cp1252"
# For the United States its: cp1252
def OpenRead(file):
bom = bomType(file)
return open(file, 'r', encoding=bom, errors='ignore')
#######################
# Testing it
#######################
fout = open("myfile1.txt", "w", encoding="cp1252")
fout.write("* hi there (cp1252)")
fout.close()
fout = open("myfile2.txt", "w", encoding="utf8")
fout.write("\u2022 hi there (utf8)")
fout.close()
# this case is still treated like codepage cp1252
# (User responsible for making sure that all utf8 files
# have a BOM header)
fout = open("badboy.txt", "wb")
fout.write(b"hi there. barf(\x81\x8D\x90\x9D)")
fout.close()
# Read Example file with Bom Detection
fin = OpenRead("myfile1.txt")
L = fin.readline()
print(L)
fin.close()
# Read Example file with Bom Detection
fin = OpenRead("myfile2.txt")
L =fin.readline()
print(L) #requires QtConsole to view, Cmd.exe is cp1252
fin.close()
# Read CP1252 with a few undefined chars without barfing
fin = OpenRead("badboy.txt")
L =fin.readline()
print(L)
fin.close()
# Check that bad characters are still in badboy codepage file
fin = open("badboy.txt", "rb")
fin.read(20)
fin.close()
回答6:
Depending on your platform, I just opt to use the linux shell file command. This works for me since I am using it in a script that exclusively runs on one of our linux machines.
Obviously this isn't an ideal solution or answer, but it could be modified to fit your needs. In my case I just need to determine whether a file is UTF-8 or not.
import subprocess
file_cmd = ['file', 'test.txt']
p = subprocess.Popen(file_cmd, stdout=subprocess.PIPE)
cmd_output = p.stdout.readlines()
# x will begin with the file type output as is observed using 'file' command
x = cmd_output[0].split(": ")[1]
return x.startswith('UTF-8')
回答7:
It is, in principle, impossible to determine the encoding of a text file, in the general case. So no, there is no standard Python library to do that for you.
If you have more specific knowledge about the text file (e.g. that it is XML), there might be library functions.
回答8:
If you know the some content of the file you can try to decode it with several encoding and see which is missing. In general there is no way since a text file is a text file and those are stupid ;)
回答9:
This site has python code for recognizing ascii, encoding with boms, and utf8 no bom: https://unicodebook.readthedocs.io/guess_encoding.html. Read file into byte array (data): http://www.codecodex.com/wiki/Read_a_file_into_a_byte_array. Here's an example. I'm in osx.
#!/usr/bin/python
import sys
def isUTF8(data):
try:
decoded = data.decode('UTF-8')
except UnicodeDecodeError:
return False
else:
for ch in decoded:
if 0xD800 <= ord(ch) <= 0xDFFF:
return False
return True
def get_bytes_from_file(filename):
return open(filename, "rb").read()
filename = sys.argv[1]
data = get_bytes_from_file(filename)
result = isUTF8(data)
print(result)
PS /Users/js> ./isutf8.py hi.txt
True
来源：https://stackoverflow.com/questions/436220/how-to-determine-the-encoding-of-text