How to Fix Typeerror a bytes-like object is required not ‘str’

In this article, I will explain why you will encounter the Typeerror a bytes-like object is required not ‘str’ error, and a few different ways to fix it.

The TypeError exception indicates that the operation you are trying to execute is not supported or not meant to be. You will usually get this error when you pass arguments of the wrong type. More details about the TypeError exception.

Apart from TypeError there are more exceptions in python. Check out this article to learn the most frequent exceptions and how to avoid them.

In this case, the bytes-like object is required message indicates the operation is excepting a bytes type; however, the type received was something else. Let’s see some examples.

Case #1: Reading from a file

This error comes up quite often when you are reading text from a file. Suppose that we have the following file, named file_sample.txt, containing the text below:

product;stock;price
bike;10;50
laptop;3;1000
microphone;5;40
book;3;9

The file contains a list of products. Each line has the product name, the current stock available, and the price. I wrote a small program that will read the file and check if there are bikes available. Here is the code:

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

bike_available = False
for line in lines:
    tmp = line.strip().lower()
    split_line = tmp.split(';')
    if split_line[0]=='bike' and int(split_line[1])>0:
        bike_available = True

print("Bikes Available? "+ str(bike_available))

And the output will be :

Traceback (most recent call last):
  Error line 7, in <module>
  	splitted_line = tmp.split(';')
TypeError: a bytes-like object is required, not 'str'    

Explanation

When I opened the file, I used this: with open('file_sample.txt', 'rb') . rb is saying to open the file in reading binary mode. Binary mode means the data is read in the form of bytes objects. Therefore if we look at line 7, I try to split a byte object using a string. That’s why the operation results in TypeError. How can I fix this?

Solution #1: Convert to a bytes object

To fix the error, the types used by the split() operation should match. The simplest solution is converting the delimiter to a byte object. I achieve that just by prefixing the string with a b

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

bike_available = False
for line in lines:
    tmp = line.strip().lower()
    split_line = tmp.split(b';') # Added the b prefix
    if split_line[0]==b'bike' and int(split_line[1])>0:
        bike_available = True

print("Bikes Available? "+ str(bike_available))

Output:

Bikes Available? True

Note I also added the b prefix, or bytes conversion, to the condition if split_line[0]==b'bike', so the types also match, and the comparison is correct.

Solution #2: Open file in text mode

Another possible solution is opening the file in text mode. I can achieve this just by removing the b from the open() action. See the following code:

with open('file_sample.txt', 'r') as f:
    lines = [x.strip() for x in f.readlines()]

bike_available = False
for line in lines:
    tmp = line.strip().lower()
    split_line = tmp.split(';')
    if split_line[0]=='bike' and int(split_line[1])>0:
        bike_available = True

print("Bikes Available? "+ str(bike_available))

Output:

Bikes Available? True

Typeerror: a bytes-like object is required, not ‘str’ replace

You could also find this error when you are trying to use the .replace() method, and the types are not matching. Here is an example:

text_in_binary = b'Sky is blue.Roses are red' #Bytes object
replaced_text = text_in_binary.replace('red','blue')
print(replaced_text)

Output:

Traceback (most recent call last):
  File line 17, in <module>
    replaced_text = text_in_binary.replace('red','blue')
TypeError: a bytes-like object is required, not 'str'

Solution #1

You can avoid this problem by making sure the types are matching. Therefore one possible solution is converting the string passed into the .replace() function( line 2), as follows:

text_in_binary = b'Sky is blue.Roses are red'
replaced_text = text_in_binary.replace(b'red',b'blue')
print(replaced_text)

Output:

b'Sky is blue.Roses are blue'

Note the result is a bytes object

Solution #2

Another way to get the types to match is converting the byte object to a string using the .decode() function( line 1), which will decode any binary content to string.

text= b'Sky is blue.Roses are red'.decode('utf-8')
print(type(text))
replaced_text = text.replace('red','blue')
print(replaced_text)

Output:

<class 'str'>
Sky is blue.Roses are blue

Please note you could also save a string in the variable text. I am using decode() because this article aims to illustrate how to manipulate bytes objects.

Typeerror: a bytes-like object is required, not ‘str’ socket

You will encounter this error when you are trying to send a string via socket. The reason is the socket.send() function expect any data to be converted to bytes. Here is a code snippet that will throw the typeerror:

import socket
mysock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
mysock.connect(('www.py4inf.com', 80))
mysock.send('GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n')

while True:
    data = mysock.recv(512)
    if ( len(data) < 1 ) :
        break
    print (data);
mysock.close()

Output:

Traceback (most recent call last):
  File line 4, in <module>
    mysock.send('GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n')
TypeError: a bytes-like object is required, not 'str'

To fix this, you will need to convert the http request inside the string (line 4) to bytes. There are two ways you can do this. Prefixing the string with b, which will convert the string to bytes:

mysock.send(b'GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n')

or using .encode() method to convert the string to bytes:

mysock.send('GET http://www.py4inf.com/code/romeo.txt HTTP/1.0\n\n'.encode())

The output will be the same in both cases:

b'HTTP/1.1 404 Not Found\r\nServer: nginx\r\nDate: Tue, 14 Jul 2020 10:03:11 GMT\r\nContent-Type: text/html\r\nContent-Length: 146\r\nConnection: close\r\n\r\n<html>\r\n<head><title>404 Not Found</title></head>\r\n<body>\r\n<center><h1>404 Not Found</h1></center>\r\n<hr><center>nginx</center>\r\n</body>\r\n</html>\r\n'

The server response indicates the file we requested doesn’t exist. However, the code created the socket, and the HTTP request hit the destination server. Therefore we can consider the error fixed

Encode and decode in python

The primary reason for this mistake is providing an incorrect data type to a function. As a result, when a function requires a bytes object as input, it’s crucial to convert the argument before passing it. This can be achieved by adding the b prefix or by utilizing the .encode() function.

Bytes to String – Decode

string_var = b'Hello'.decode('utf-8')
print(type(string_var))

Output:

<class 'str'>

String to Bytes – Encode

bytes_var = 'Hello'.encode()
print(type(bytes_var))

Output:

<class 'bytes'>

Conclusion

To summarise, when you encounter this error, it is important to double-checking the types you are used and make sure the types match, and you are not passing a wrong type to a function. I hope this helps and thanks for reading, and supporting this blog. Happy Coding!

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