✋ Update: This post was originally published on my blog decodingweb.dev, where you can read the latest version for a 💯 user experience. ~reza
If you’re getting the “AttributeError: ‘str’ object has no attribute ‘decode’ error, you’re probably calling decode()
on a string value (str
object) in Python 3.
Here’s what the error message looks like in the Python shell:
>>> username = 'admin'
>>> username.decode()
Traceback (most recent call last):
File "", line 1, in
AttributeError: 'str' object has no attribute 'decode'. Did you mean: 'encode'?
>>>
Python 3 stores a string as a sequence of Unicode code points and hence there's no need to decode them.
The new str
class doesn't even implement the decode()
method. If you call this method on a Python 3 string, you'll get the infamous "AttributeError: 'str' object has no attribute 'decode'" error.
Let's confirm it by using the hasattr()
function:
username = 'admin'
hasattr(username, 'decode') # False
As you can see, the hasattr()
function returns False
in this case.
It wasn't the case with Python 2, though. In Python 2, you can store strings as:
- 8-bit strings (by default)
- Unicode objects - by using the
u
prefix before a string literal (e.g.,u'somestring'
) or by using the unicode constructor (unicode('somestring')
)
In Python 2, strings expose a decode()
function. In Python 3, however, you don't have to decode your strings as all string values are assumed to be in Unicode.
Encoding and Decoding in Python 3
In Python 3, you can only call the decode()
method on a bytes
object - when you want to decode it into a Unicode string.
In the Python 3 context:
- Encoding is the process of converting a
str
object to abytes
object - Decoding is the process of converting a
bytes
object to astr
object based on the specified encoding.
Calling encode()
on a string returns a bytes
object:
username = 'admin'
username_encoded = username.encode()
print(type(username_encoded)) # <class 'bytes'>
print(hasattr(username_encoded, 'decode')) # True
print(username_encoded) # b'admin'
If you're working with a legacy code and have no control over the value (whether it's a bytes
or str
object), you can use a try/catch block to avoid a possible attribute error.
try:
username_decoded = username.decode('UTF-8')
# Do something here
except AttributeError:
pass
But as mentioned earlier, you don't usually need to decode your Python string to Unicode as it already is.
And that's how you fix the "AttributeError: 'str' object has no attribute 'decode'" error in Python 3.
I hope that solves your problem. Thanks for reading.
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