Python 3 urllib produces TypeError: POST data should be bytes or an iterable of bytes. It cannot be of type str

I am trying to convert working Python 2.7 code into Python 3 code and I am receiving a type error from the urllib request module.

I used the inbuilt 2to3 Python tool to convert the below working urllib and urllib2 Python 2.7 code:

import urllib2
import urllib

url = "https://www.customdomain.com"
d = dict(parameter1="value1", parameter2="value2")

req = urllib2.Request(url, data=urllib.urlencode(d))
f = urllib2.urlopen(req)
resp = f.read()

The output from the 2to3 module was the below Python 3 code:

import urllib.request, urllib.error, urllib.parse

url = "https://www.customdomain.com"
d = dict(parameter1="value1", parameter2="value2")

req = urllib.request.Request(url, data=urllib.parse.urlencode(d))
f = urllib.request.urlopen(req)
resp = f.read()

When the Python 3 code is run the following error is produced:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-56-206954140899> in <module>()
      5 
      6 req = urllib.request.Request(url, data=urllib.parse.urlencode(d))
----> 7 f = urllib.request.urlopen(req)
      8 resp = f.read()

C:\Users\Admin\Anaconda3\lib\urllib\request.py in urlopen(url, data, timeout, cafile, capath, cadefault, context)
    159     else:
    160         opener = _opener
--> 161     return opener.open(url, data, timeout)
    162 
    163 def install_opener(opener):

C:\Users\Admin\Anaconda3\lib\urllib\request.py in open(self, fullurl, data, timeout)
    459         for processor in self.process_request.get(protocol, []):
    460             meth = getattr(processor, meth_name)
--> 461             req = meth(req)
    462 
    463         response = self._open(req, data)

C:\Users\Admin\Anaconda3\lib\urllib\request.py in do_request_(self, request)
   1110                 msg = "POST data should be bytes or an iterable of bytes. " \
   1111                       "It cannot be of type str."
-> 1112                 raise TypeError(msg)
   1113             if not request.has_header('Content-type'):
   1114                 request.add_unredirected_header(

TypeError: POST data should be bytes or an iterable of bytes. It cannot be of type str.

I have also read two other tickets (ticket1 and ticket2) which mentioned encoding the date.

When I changed the line f = urllib.request.urlopen(req) to f = urllib.request.urlopen(req.encode('utf-8')) I received the following error: AttributeError: 'Request' object has no attribute 'encode'

I am stuck as to how to make the Python 3 code work. Could you please help me?

From the docs Note that params output from urlencode is encoded to bytes before it is sent to urlopen as data:

data = urllib.parse.urlencode(d).encode("utf-8")
req = urllib.request.Request(url)
with urllib.request.urlopen(req,data=data) as f:
    resp = f.read()
    print(resp)

Try this:

url = 'https://www.customdomain.com'
d = dict(parameter1="value1", parameter2="value2")

f = urllib.parse.urlencode(d)
f = f.encode('utf-8')

req = urllib.request.Request(url, f)

Your problem lies in the way you were handling the dictionary.