try:
x = int('cat')
except Exception as e:
pass
print(e) # <- NameError: name 'e' is not defined
e = 'before'
try:
x = int('cat')
except Exception as e:
e2 = e
print(e)
print(e2) # <- This works!
print(e) # <- NameError: name 'e' is not defined
https://stackoverflow.com/questions/24271752
https://docs.python.org/3/reference/compound_stmts.html#exce...
But the language makes sense at a lower level, scopes, values, bindings have their mostly reasonable rules that are not hard to follow.
In comparison python seems like an infinite tower of ad-hoc exceptions over ad-hoc rules, sure it looks simpler but anywhere you look you discover an infinite depth of complexity [1]
[0] and how half of the complaints are a conjugation of "I don't like that NaNs exist
[1] my favourite example is how dunder methods are a "synchronized view" of the actual object behaviour, that is in a + b a.__add__ is never inspected, instead at creation time a's add behaviour is defined as its __add__ method but the association is purely a convention, eg any c extension type need to reimplement all these syncs to expose the correct behaviour and could for funzies decide that a type will use __add__ for repr and __repr__ for add
The "random things" make it practically impossible to figure out what will happen without learning a whole bunch of seemingly arbitrary, corner-case-specific rules (consider the jsdate.wtf test currently making the rounds). And no, nobody is IMX actually simply complaining about NaNs existing (although the lack of a separate integer type does complicate things).
Notice that tests showcasing JavaScript WTFery can work just by passing user data to a builtin type constructor. Tests of Python WTFery generally rely on much more advanced functionality (see e.g. https://discuss.python.org/t/quiz-how-well-do-you-know-pytho...). The only builtin type constructor in Python that I'd consider even slightly surprising is the one for `bytes`/`bytearray`.
Python's scoping is simple and makes perfect sense, it just isn't what you're used to. (It also, unlike JavaScript, limits scope by default, so your code isn't littered with `var` for hygiene.) Variables are names for objects with reference semantics, which are passed by value - exactly like `class` types in C# (except you don't have to worry about `ref`/`in`/`out` keywords) or non-primitives in Java (notwithstanding the weird hybrid behaviour of arrays). Bindings are late in most places, except notably default arguments to functions.
I have no idea what point you're trying to make about __add__; in particular I can't guess what you think it should mean to "inspect" the method. Of course things work differently when you use the C API than when you actually write Python code; you're interacting with C data structures that aren't directly visible from Python.
When you work at the Python level, __add__/__iadd__/__radd__ implement addition, following a well-defined protocol. Nothing happens "at creation time"; methods are just attributes that are looked up at runtime. It is true that the implementation of addition will overlook any `__add__` attribute attached directly to the object, and directly check the class (unlike code that explicitly looks for an attribute). But there's no reason to do that anyway. And on the flip side, you can replace the `__add__` attribute of the class and have it used automatically; it was not set in stone when the class was created.
I'll grant you that the `match` construct is definitely not my favourite piece of language design.
At runtime when evaluating a + b no dunder method is looked up and there is no guarantee that a + b === a.__anydunder__(b) https://youtu.be/qCGofLIzX6g
What i mean with weird scoping is
def foo():
e = 'defined'
try:
raise ValueError
except Exception as e:
print(e)
print(e) # this will error out
foo()
I agree that that Javascripts standard library is horrible the jsdate.wtf is an extreme but apt example, IMO most of these are solved with some "defensive programming" but I respect other opinions here.
> And no, nobody is IMX actually simply complaining about NaNs existing
I watched many Javascript WTF! videos on youtube and NaNs and [2] == "2" were usually 90% of the content.
It's not that odd, since it's the only situation where you cannot keep it bounded, unless you enjoy having variables that may or may not be defined (Heisenberg variable?), depending on whether the exception has been raised or not?
Compare with the if statement, where the variable in the expression being tested will necessarily be defined.
for i in range(0):
passIs there any chance this would cause trouble though? Furthermore, what would be the need of having this variable accessible after the except block? In the case of a for block, it could be interesting to know at which point the for block was "passed".
So, maybe "None" answers your question?
if False:
x = 7
print(x)
print(x)
^
NameError: name 'x' is not defined
if <true comparison here>:
x = 5
print(x) # <- should give name error?In the case of an if like in your example, no provision is made about the existence of x. It could have been defined earlier, and this line would simply update its value.
Your example:
if True:
x = 5
print(x) # 5
x = 1
if False:
x = 5
print(x) # 1
if False:
x = 5
print(x) # ???
While investigating this question, I tried the following:
x = 3
try:
raise Exception()
except Exception as x:
pass
print(x) # <- what should that print?edit: writing from phone on couch and the laptop... looks far, far away...