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.
What years of dynamic typing brainrot does to mf
bool_
via Numpy is its own object, and it’s fundamentally different frombool
in Python (which is itself a subclass ofint
, whereasbool_
is not).They are used similarly, but they’re similar in the same way a fork and a spork can both be used to eat spaghetti.
And do you eat that spaghetti out of a bool?
So you have to do dumb workarounds like declaring every
bool
values asbool | np.bool_
or castingbool_
down tobool
.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)-5**2 is apparently -25 because of the order of operations)
Which is correct
Well, the link doesn’t load for me, so if that’s smth related to python and not a justification of the behavior from math’s pov, I know that’s expected. Hence,
because of the order of operations
But just as well is “1” + 2.
I don’t see how your example is ‘funny’. That’s what you expect to get. -52 is -25. (-5)2 = 25.
"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:
- JS
- TS
- Java
- C#
- C++
- Kotlin
- Groovy
- Scala
- PowerShell
What produces a number, instead of a string:
- PHP
- SQL
- Perl
- VB
- Lua
What it doesn’t work in:
- R
- C
- Go
- Swift
- Rust
- Python
- Pascal
- Ruby
- Objective C
- Julia
- Fortran
- Ada
- Dart
- D
- Elixir
And MATLAB appears to produce 51, wtf idk
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 following-
identify 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
-
Honestly, after having served on a Very Large Project with Mypy everywhere, I can categorically say that I hate it. Types are great, type checking is great, but applying it to a language designed without types in mind is a recipe for pain.
In my experience, mypy + pydantic is a recipe for success, especially for large python projects
I wholeheartedly agree. The ability to describe (in code) and validate all data, from config files to each and every message being exchanged is invaluable.
I’m actively looking for alternatives in other languages now.
You’re just describing parsing in statically-typed languages, to be honest. Adding all of this stuff to Python is just (poorly) reinventing the wheel.
Python’s a great language for writing small scripts (one of my favorite for the task, in fact), but it’s not really suitable for serious, large scale production usage.