CODEWITHSUNDEEP
pythontwisted
tesla john
tesla john

Reputation: 350

cannot use a bytes pattern on a string-like object with agent.request

I am learning - how to send a request to the browser with twisted then get the headers and print them. However, I find myself getting the following error when I run:

 python agent_request.py http://www.google.com/

> cannot use a bytes pattern on a string-like object

import sys
from twisted.internet import reactor
from twisted.web.client import Agent
from twisted.web.http_headers import Headers

def printHeaders(response):
    print('HTTP version:', response.version)
    print('Status code:', response.code)
    print('Status phrase:', response.phrase)
    print('Response headers:')
    for header, value in response.headers.getAllRawHeaders():
        print(header, value)

def printError(failure):
    print(sys.stderr, failure) 

def stop(result):
    reactor.stop()
    
if len(sys.argv) != 2:
    print(sys.stderr, "Usage: python print_metadata.py URL") 
    exit(1)

agent = Agent(reactor)

headers = Headers({'User-Agent': ['Twisted WebBot'],
                   'Content-Type': ['text/x-greeting']})
d = agent.request('HEAD', sys.argv[1], headers=headers)
d.addCallbacks(printHeaders, printError)
d.addBoth(stop)
reactor.run()

Expected output:

HTTP version: ('HTTP', 1, 1)
    Status code: 200
Status phrase: OK
    Response headers:
    X-Xss-Protection ['1; mode=block']
    Set-Cookie ['PREF=ID=b1401ec53122a4e5:FF=0:TM=1340750440...
    Expires ['-1']
    Server ['gws']
    Cache-Control ['private, max-age=0']
    P3p ['CP="This is not a P3P policy! See http://www.google.com/support/...
    Content-Type ['text/html; charset=ISO-8859-1']
    X-Frame-Options ['SAMEORIGIN']

Upvotes: 0

Views: 502

Answers (1)

Jean-Paul Calderone
Jean-Paul Calderone

Reputation: 48335

On Python 3 sys.argv is a list of str. However, Agent.request accepts a value of type bytes as its 2nd argument. Since sys.argv[1] is a value of type str something goes wrong somewhere in the implementation and you get this obscure exception.

If you encode sys.argv[1] to bytes (eg sys.argv[1].encode("ascii")) and pass the result to agent.request then you'll get past this error.

Upvotes: 2

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