Home/ Questions/The: ''Cannot use a string pattern on a bytes-like object'' error - What should I do?
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Kaira O'Neill
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Asked: 2022-05-18T18:45:26+00:00 In:

The: ”Cannot use a string pattern on a bytes-like object” error – What should I do?

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I get the “cannot use a string pattern on a bytes-like object” error as the title says. How can I fix it so the error goes away? Here is my detail:

import urllib.request
 import re
 
 url = "http://www.google.com"
 regex = r'<title>(,+?)</title>'
 pattern = re.compile(regex)
 
 with urllib.request.urlopen(url) as response:
  html = response.read()
 
 title = re.findall(pattern, html)
 print(title)

When I operated it, I received the error text:

Traceback (most recent call last):
  File "path\to\file\Crawler.py", line 11, in <module>
  title = re.findall(pattern, html)
  File "C:\Python33\lib\re.py", line 201, in findall
  return _compile(pattern, flags).findall(string)
 TypeError: can't use a string pattern on a bytes-like object

I appreciate any help from you.

python-3.x
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2 Answers

  1. Best Answer
    Expert

    The cause:

    You are facing up with this error because you are attempting to use a string to match with a bytes object. Moreover, python is not be informed that the bytes have been encoded. Therefore, the error happens after you run your program.

    Solution:

    To fix this error, you must change html (a bytes object) into a string by using .decode as following:

    html = response.read().decode('utf-8')

    A bytes regex also is not bad method for this error, so you can use it:

    regex = rb'<title>(,+?)</title>' 
#        ^

    Let’s read this article to get more knowledge Change bytes to a Python String.

    • 0

  2. Your regex is a string but html bytes. 

    >>> type(html)
<class 'bytes'>

    Because python does not know the encoded bytes, it throws an error when you attempt to use string regex.

    You can decode add bytes to a string. 

    html = html.decode('ISO-8859-1') # encoding may vary!
title = re.findall(pattern, html) # no more error

    You can also use a bytes regex 

    regex = rb'<title>(,+?)</title>'
# ^

    This particular context allows you to get the encoding using the response headers. 

    with urllib.request.urlopen(url) as response:
 encoding = response.info().get_param('charset', 'utf8')
 html = response.read().decode(encoding)

    For more information, see the urlopen documentation .

    • 14

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