Python – TypeError: a bytes-like object is required, not ‘str’ when writing to a file in Python3

bytefilepythonpython-3.xstring

I've very recently migrated to Py 3.5.
This code was working properly in Python 2.7:

with open(fname, 'rb') as f:
    lines = [x.strip() for x in f.readlines()]

for line in lines:
    tmp = line.strip().lower()
    if 'some-pattern' in tmp: continue
    # ... code

After upgrading to 3.5, I'm getting the:

TypeError: a bytes-like object is required, not 'str'

error on the last line (the pattern search code).

I've tried using the .decode() function on either side of the statement, also tried:

if tmp.find('some-pattern') != -1: continue

– to no avail.

I was able to resolve almost all 2:3 issues quickly, but this little statement is bugging me.

Best Answer

You opened the file in binary mode:

with open(fname, 'rb') as f:

This means that all data read from the file is returned as bytes objects, not str. You cannot then use a string in a containment test:

if 'some-pattern' in tmp: continue

You'd have to use a bytes object to test against tmp instead:

if b'some-pattern' in tmp: continue

or open the file as a textfile instead by replacing the 'rb' mode with 'r'.

Related Solutions

Python – TypeError: ‘module’ object is not callable

socket is a module, containing the class socket.

You need to do socket.socket(...) or from socket import socket:

>>> import socket
>>> socket
<module 'socket' from 'C:\Python27\lib\socket.pyc'>
>>> socket.socket
<class 'socket._socketobject'>
>>>
>>> from socket import socket
>>> socket
<class 'socket._socketobject'>

This is what the error message means:
It says module object is not callable, because your code is calling a module object. A module object is the type of thing you get when you import a module. What you were trying to do is to call a class object within the module object that happens to have the same name as the module that contains it.

Here is a way to logically break down this sort of error:

"module object is not callable. Python is telling me my code trying to call something that cannot be called. What is my code trying to call?"
"The code is trying to call on socket. That should be callable! Is the variable socket is what I think it is?`
I should print out what socket is and check print socket

Python – Using pickle.dump – TypeError: must be str, not bytes

The output file needs to be opened in binary mode:

f = open('varstor.txt','w')

needs to be:

f = open('varstor.txt','wb')

Best Answer

Related Solutions

Python – TypeError: ‘module’ object is not callable

Python – Using pickle.dump – TypeError: must be str, not bytes

Related Topic