Menu
Consider this code snippet:
my_string = 'asdf'
print(my_string is 'xfje') #R0123
Pylint returns a recommendation R0123 on the second line, which I was unable to find on the error message wiki. There is a mention of it in this part of the docs, though:
literal-comparison (R0123):
Comparison to literal Used when comparing an object to a literal, which is usually what you do not want to do, since you can compare to a different literal than what was expected altogether.
This explanation is not helpful at all to me. I know that using is for comparison between two string objects may lead to different results than expected, but for comparison of object to literal, it is identical to == . And when using ==, the error disappears.
Why should I not use is here?
559
Python strings equality can be checked using == operator or __eq__() function. Python strings are case sensitive, so these equality check methods are also case sensitive.
Description: Used when comparing an object to a literal, which is usually what you do not want to do, since you can compare to a different literal than what was expected altogether.
Python String comparison can be performed using equality (==) and comparison (<, >, != , <=, >=) operators. There are no special methods to compare two strings.
is checks that the left hand argument holds the exact same reference as the right hand argument. This is fine for None which is a singleton, but is usually a bad idea for other types, where multiple instances can have the same logical value.
Consider, e.g. the following example:
>>> my_string = ''.join([c for c in 'xfje'])
>>> print my_string
xfje
>>> print my_string == 'xfje'
True
>>> print my_string is 'xfje'
False
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
