Python 3 TypeError: Can’t convert ‘bytes’ object to str implicitly

By mkyong | Updated: September 3, 2015

Viewed: 2,329 (+9 pv/w)

Tags: python error python3

Converting a Python 2 socket example to Python 3

import sys
import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("whois.arin.net", 43))
s.send((sys.argv[1] + "\r\n").encode())

response = ""
while True:
    data = s.recv(4096)
    response += data
    if not data:
        break
s.close()
print(response)

If compile with Python 3, it prompts the following error?

Traceback (most recent call last):
  File "C:\repos\hc\whois\python\whois.py", line 12, in <module>
    response += data
TypeError: Can't convert 'bytes' object to str implicitly

Solution

In Python 3, the socket returns data as bytes (it was string in Python 2). Since the response is a string, you can’t add two different types (bytes + string) directly. To fix it, you need to convert the type :

#Solution 1 Convert the response from string to bytes

import sys
import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("whois.arin.net", 43))
s.send((sys.argv[1] + "\r\n").encode())

#Convert response to bytes 
response = b""
# or use encode()
#response = "".encode()

while True:
    data = s.recv(4096)
    response += data
    if not data:
        break
s.close()
print(response.decode())

#Solution 2 Convert the data from bytes to string

import sys
import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("whois.arin.net", 43))
s.send((sys.argv[1] + "\r\n").encode())

response = ""
while True:
    data = s.recv(4096)
    #convert data from bytes to string
    #response += data
    response += data.decode()
    if not data:
        break
s.close()
print(response)

References

1. Python 3 Built-in Types
2. Python Whois client example