CODEWITHSUNDEEP
pythondecodeencode
carl
carl

Reputation: 4436

How to determine how a (downloaded) byte string is encoded in python?

I am trying to download a file and write it to disk, but somehow I am lost in encoding decoding land.

from urllib.request import urlopen
url = "http://export.arxiv.org/e-print/supr-con/9608001"
with urllib.request.urlopen(url) as response:
    data = response.read()
    filename = 'test.txt'
    file_ = open(filename, 'wb')
    file_.write(data)
    file_.close()

Here data is a byte string. If I check the file I find a bunch of strange characters. I tried

import chardet
the_encoding = chardet.detect(data)['encoding']

but this results in None. So I don't really know how the data I downloaded is encoded?

If I just type "http://export.arxiv.org/e-print/supr-con/9608001" into the browser, it downloads a file that I can view with a text editor and it's a perfectly fine .tex file.

Upvotes: 0

Views: 174

Answers (1)

JosefZ
JosefZ

Reputation: 30238

Apply the python-magic library.

python-magic is a Python interface to the libmagic file type identification library. libmagic identifies file types by checking their headers according to a predefined list of file types. This functionality is exposed to the command line by the Unix command file.

Commented script (works on Windows 10, Python 3.8.6):

# stage #1: read raw data from a url
from urllib.request import urlopen
import gzip
url = "http://export.arxiv.org/e-print/supr-con/9608001"
with urlopen(url) as response:
    rawdata = response.read()

# stage #2: detect raw data type by its signature
print("file signature", rawdata[0:2])
import magic
print( magic.from_buffer(rawdata[0:1024]))

# stage #3: decompress raw data and write to a file
data = gzip.decompress(rawdata)
filename = 'test.tex'
file_ = open(filename, 'wb')
file_.write(data)
file_.close()

# stage #4: detect encoding of the data ( == encoding of the written file)
import chardet
print( chardet.detect(data))

Result: .\SO\68307124.py

file signature b'\x1f\x8b'
gzip compressed data, was "9608001.tex", last modified: Thu Aug  8 04:57:44 1996, max compression, from Unix
{'encoding': 'ascii', 'confidence': 1.0, 'language': ''}

Upvotes: 1

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