Why does comparison of bytes with str fails in Python3
Solution 1
In Python 2.x, the design goal for unicode is to enable transparent operations between unicode & byte strings by implicitly converting between the 2 types. When you do the comparison u"" == ""
, the unicode
LHS is automatically encoded into a byte string first, and then compared to the str
RHS. That's why it returned True
.
In contrast, Python 3.x, having learned from the mess of unicode that was in Python 2, decided to make everything about unicode vs. byte strings explicit. Thus, b"" == ""
is False
because the byte string is no longer automatically converted to unicode for comparison.
Solution 2
In python 3 string is Unicode . The type used to hold text is str
and the type used to hold data is bytes
.
the
str
andbytes
types cannot be mixed, you must always explicitly convert between them. Usestr.encode()
to go fromstr
tobytes
, andbytes.decode()
to go from bytes tostr
.
Therefore, if you do b"".decode() == ""
you'll get True
:
>>> b"".decode() == ""
True
For more info read Text Vs. Data Instead Of Unicode Vs. 8-bi
Solution 3
The designers decided to not assume an encoding for coercion when comparing bytes to strings, so it falls under the default behavior of Python 3.x whereby comparisons containing differing types fail.
steffen
I am a Python freak and data nerd. Also, I am experimenting with creating videos on youtube. About Python and data. ¯(°_o)/¯ https://www.youtube.com/channel/UCG9XNnq9LodijOBpIVy1ILg
Updated on November 16, 2020Comments
-
steffen over 3 years
In Python3 this expression evaluates as
False
:b"" == ""
while in Python2 this comparison is
True
:u"" == ""
Checking for identity with
is
obviously fails in both cases.But why would they implement such a behaviour in Python3?