Explanation: Python is a programming language. Numpy is a library for python that makes it possible to run large computations much faster than in native python. In order to make that possible, it needs to keep its own set of data types that are different from python’s native datatypes, which means you now have two different bool
types and two different sets of True
and False
. Lovely.
Mypy is a type checker for python (python supports static typing, but doesn’t actually enforce it). Mypy treats numpy’s bool_
and python’s native bool
as incompatible types, leading to the asinine error message above. Mypy is “technically” correct, since they are two completely different classes. But in practice, there is little functional difference between bool
and bool_
. So you have to do dumb workarounds like declaring every bool values as bool | np.bool_
or casting bool_
down to bool
. Ugh. Both numpy and mypy declared this issue a WONTFIX. Lovely.
these dumb workarounds prevent you from shooting yourself on the foot and not allowing JS-level shit like
"1" + 2 === "12"
Well, C has implicit casts, and it’s not that weird (although results in some interesting bugs in certain circumstances). Python is also funny from time to time, albeit due to different reasons (e.g.
-5**2
is apparently -25 because of the order of operations)I don’t see how your example is ‘funny’. That’s what you expect to get. -52 is -25. (-5)2 = 25.
And how’s that different from js’s
"1" + 2
? One can always convert a number to string, and only sometimes – a string to a number, so it’s pretty logical to go with the former."1" + 2 === "12"
is not unique to JS (sans the requirement for the third equals sign), it’s a common feature of multiple strongly typed languages. imho it’s fine.EDIT: I did some testing:
What it works in:
What produces a number, instead of a string:
What it doesn’t work in:
And MATLAB appears to produce 51, wtf idk
The numeric value of the ‘1’ character (the ASCII code / Unicode code point representing the digit) is 49. Add 2 to it and you get 51.
C (and several related languages) will do the same if you evaluate
'1' + 2
.Oh that makes sense. I didn’t consider it might be treated as a char
The JS thing makes perfect sense though,
“1” is a string. You declared its type by using quotes.
myString = "1"
in a dynamically typed language is identical to writingstring myString = "1"
in a statically typed language. You declare it in the symbols used to write it instead of having to manually write outstring
every single time.2 is an integer. You know this because you used neither quotes nor a decimal place surrounding it. This is also explicit.
"1" + 2
, if your interpreter is working correctly, should do the followingidentify the operands from left to right, including their types.
note that the very first operand in the list is a
string
type as you explicitly declared it as such by putting it in quotes.cast the following operands to
string
if they are not already.use the string addition method to add operands together (in this case, this means concatenation).
In the example you provided,
"1" + 2
is equivalent to"1" + "2"
, but you’re making the interpreter do more work.QED:
"1" + 2
should, in fact,=== "12"
, and your lack of ability to handle a language where you declare types by symbols rather than spending extra effort writing the type out as a full english word is your own shortcoming. Learn to declare and handle types in dynamic languages better, don’t blame your own misgivings on the language.Signed, a software engineer.
TypeError is also a correct response, though, and I think many folks would say makes more sense. Is an unnecessary footgun