I thought it was default since python 3.
replies(2):
This change seems to be about things like open('filename', mode='r') mainly on Windows where the default encoding is not UTF-8 and so you'd have to specify open('filename', mode='r', encoding='UTF-8')
You got it kind of backwards. `str` are sequence of unicode codepoints (not UTF-8, which is a specific encoding for unicode codepoints), without reference to any encoding. `bytes` are arbitrary sequence of octets. If you have some `bytes` object that somehow stands for text, you need to know that it is text and what its encoding is to be able to interpret it correctly (by decoding it to `str`).
And, if you got a `str` and want to serialize it (for writing or transmitting), you need to choose an encoding, because different encodings will generate different `bytes`.
As an example :
>>> "évènement".encode("utf-8") b'\xc3\xa9v\xc3\xa8nement'
>>> "évènement".encode("latin-1") b'\xe9v\xe8nement'
It’s worse than that, actually: UTF-8 is a specific encoding for sequences of Unicode scalar values (which means: code points minus the surrogate range U+D800–U+DFFF). Since str is a sequence of Unicode code points, this means you can make strings that cannot be encoded in any standard encoding:
>>> '\udead'.encode('utf-16')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'utf-16' codec can't encode character '\udead' in position 0: surrogates not allowed
>>> '\ud83d\ude41'.encode('utf-8')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
UnicodeEncodeError: 'utf-8' codec can't encode character '\ud83d' in position 0: surrogates not allowed