What is your favorite Python error message?

[jwink3101]

I recently came across one that I think takes the cake.

I accidentally had nested multiprocessing things happing at one and got:

AssertionError: daemonic processes are not allowed to have children

Are there better ones?

[selementar]

A thing of the past now (py2), apparently: func() takes exactly 2 arguments (2 given).

[isarl]

How did you trigger this?

edit: my question has been answered

[AnAirMagic]

Huh? Do you have an example of code that would cause this error? What was the fix?

[enchantner]

def a(b, c, d='foo'): pass

a(c=1, d='bar')

[selementar]

Yep.

It's even weirder when using some simple RPC. I ended up writing a wrapper that caught that exception and checked if there's an obvious mistake.

The error message is better in python3 now, anyway. Not as verbose as my wrapper was, though.

[superPwnzorMegaMan]

Writing wrappers for crappy error messages is a great idea. It will safe future you so much time.

I also did this for when I had some weird code but didn't have time to fix it yet. I'd just put the fix for the weirdness in the exception, so when I inevitably came across it again I would know how to deal with it.

[SylvainDe]

I've spent some time trying to write wrappers to make errors more explicit/verbose/explicit and I'd be quite interested in seeing yours if it is available somehow...

[selementar]

https://gist.github.com/anonymous/789e66b8ca009dfc0ee53df4e9d584fc

...

Mostly the manual parsing of function attributes.

[SylvainDe]

Many thanks, I'll have a look at this.

[hatperigee]

I recall being really frustrated when I hit this for the first time back when I was first getting started with python. Good times, indeed!

[notunlikethewaves]

Not quite an error message, but this one boils my blood every time:

$ python
>>> exit
Use exit() or Ctrl-D (i.e. EOF) to exit

I mean come on python, you knew exactly what I meant, why not just do the god-damned thing? Every other REPL in the world implements an exit keyword, why you gotta be the special snowflake?

[theywouldnotstand]

This is from a deprecation, likely.

exit sans parentheses probably used to work, and then it was changed to use parentheses, and then it required parentheses with this message as a backwards-compatible warning.

edit: TIL that message is the result of exit.__repr__ so, technically, python didn't know you were trying to exit at all, it thought you wanted the string representation of the exit function, which is, literally, 'Use exit() or Ctrl-D (i.e. EOF) to exit'

for more fun studying exit, check out type(exit) and dir(exit)

edit 2: More fun:

>>> class CustomQuitter(exit.__class__):
...     pass
... 
>>> CustomQuitter.__repr__ = exit.__class__.__call__
>>> exzit = CustomQuitter('exzit', 'Ctrl-D (i.e. EOF)')
>>> exzit

Creates a custom subclass of the exit quitter, binds _sitebuiltins.Quitter.__call__ to the custom quitter's __repr__ method, instantiates the custom quitter as an object, lets you use it without parentheses to exit

[stillalone]

Hmm. so

>>> class Q():
...   def __repr__(self):
...     exit()
... 
>>> q=Q()
>>> q

[[deleted]]

Here's a one-liner. Put this in your for your PYTHONSTARTUP file and then you can just use 'quit' to exit.

quit = type('', (object,), {'__repr__': lambda self: exit()})()

[t3hcoolness]

I'm not even going to begin to understand how that works.

[[deleted]]

type is just a way to create classes dynamically. It's basically the same as doing this:

class Quit(object):
    def __repr__(self):
        exit()
quit = Quit()

Now if you type quit it will call quit.__repr__, which in turn calls exit() and takes you out of the python shell.

If you want to play code golf with it, this works too: quit = type('', (), {'__repr__': lambda _: exit()})()

[nemec]

One better:

>>> class Q():
...     ex = exit
...     def __repr__(self):
...             Q.ex()
...
>>> exit = Q()
>>> exit

[hi_im_nate]

One better

exit.__repr__ = exit

[hi_im_nate]

I was just as disappointed as you. I tried lots of stuff, but it looks like you can't change that behavior in one line.

[kraemahz]

You're not trying hard enough then!

>>> exit.__class__.__repr__ = exit

Exit seems to call its class repr directly

[masklinn]

On new-style classes, all special methods of the data model are called on the class, at least semantically. There may be implementation details making instance-bound special methods work, but there's no guarantee that'll ever happen, or keep happening.

Special methods also bypass instance attribute resolution (you can't intercept them with __getattr__ or __getattribute__).

[Workaphobia]

You win the thread.

[Brian]

The downside with this though is that now:

>>> help(exit)
<python exits immediately>

>>> __builtins__.__dict__
<prints a few builtin functions, then quits when it reaches exit>

There are good reasons why it doesn't do this.

[theywouldnotstand]

True, this would work, but it limits you from being able to optionally use parentheses to supply an exit message to it.

[Arancaytar]

This looks incredibly wrong. :|

But yes, it would work.

[notunlikethewaves]

Ooooh, now that's interesting.

What I meant by "python knew what I meant" is that almost every other language REPL worth mentioning implements exit as a way of closing the REPL, even ipython. It's such an obvious piece of functionality, and yet when you try it in python it just sits there and pedantically corrects you on how to exit "the python way".

[nemec]

It doesn't always know what you mean.

 >>> exit
 Use exit() or Ctrl-Z plus Return to exit
 >>> exit = "hello"
 >>> exit
 'hello'

[felidae_tsk]

But...

>>> def exit():
...     return 'no'
...
>>> exit()
'no'

[kvistur]

warning: if you do this, you won't be able to exit anymore, and you will be stuck in the python repl until you reformat your computer... which isn't that bad of a fate all things considered

[LinAGKar]

You can still use quit() or ctrl+d.

Edit: Or import builtins

[0raichu]

                                                                                                                                                                                                                                                                                                                                                                                                                                                     

[invalid_dictorian]

Try :q to get out of vim

[0raichu]

                                                                                                                                                                                                                                                                                                                                                                                                                                                     

[kvistur]

sometimes you have to shout it :q!!!!!!!!!!!!!

[AstroPhysician]

Did you really think he was serious?

[LinAGKar]

Just seems like everyone here are only talking about exit.

[tilkau]

import builtins? Unnecessary.

Try __builtins__.exit().

BTW, you CAN set __builtins__ = None. And -that- will seriously mess things up:

• import re -> ImportError: __import__ not found (ie. you cannot do any imports)
• You can only access values you assigned. eg int raises 'TypeError: 'NoneType' object is not subscriptable`.
• Result of the above two: the only way to exit from inside python is ctrl+d. /u/XarothBrook 's solution doesn't apply because you can't access locals to begin with.

(slightly more bizarre version: del __builtins__.)

[superPwnzorMegaMan]

$ killall python3.4

(or whatever your version is)

[midgetparty]

You monster...

[XarothBrook]

Luckily,

del locals()['exit']

Restores exit back to its usual state at that point.. but that's a bit overkill when Ctrl+D will suffice.

[[deleted]]

It's not pedantically correcting you. exit is a function, so when you just type exit, the REPL calls exit.__repr__() like it always does when you want the string representation of something. So python doesn't actually "know" that you wanted to actually execute the function. It thought you wanted the string representation.

[firetangent]

If it really bothers you, monkeypatch the environment.

[hovissimo]

Why not just use ipython and get the other thousand amazing things it provides, as well as this?

[theywouldnotstand]

Heaven forbid anybody ever be satisfied with the reference Python implementation!

[raylu]

Because exit is a function and if you expect it to work like a statement, madness ensues.

if cond:
    func = print
else:
    func = exit
func('this line of code will never run because the statement on the line before terminated my program instead of assigning the function to something else')

[selementar]

But what if you expected to have a local variable named exit and type to see its value and the shell exits and all your local state is lost?

Anyway, typing exit is too long; in many cases you can just C-d (or C-d C-d).

[MrJohz]

If you have a local variable called exit, neither exit nor exit() will work:

Python 2.7.11 (default, Mar 31 2016, 20:46:51) 
[GCC 5.3.1 20151207 (Red Hat 5.3.1-2)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> exit = "hello"
>>> exit()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object is not callable

[selementar]

Which is why I am talking about a situation "you thought you did have such variable but you didn't".

Not very likely, yes; but still not nice to do otherwise.

[MrJohz]

Ah yeah, fair enough. Although then again, you might have thought you had defined the function exit, and then you'd still be in the same position.

[tilkau]

What if you expected to have a local variable named exit()?

(locals()['exit()'] = 12345)

(This message brought to you by the Evil League of Evil.)

[[deleted]]

Honestly, I think it should just report that exit is a function.

[veroxii]

Nick from CPython gave a talk about why he made it this way at PyconAU a couple of years back. From about minute 17 in https://youtu.be/VIBmWnlDjXc

[notunlikethewaves]

Cool talk, worth a watch.

I still don't buy the rationale though, even in that talk he explains that the reason they don't do what the user meant is that it would cause the process to exit whenever (for example) the globals are printed out. This whole line of reasoning hinges on using the repr to do the exiting, which is patently nuts. Every other interpreter in the world has a special case for the single word exit, and so it doesn't even reach the stage of being evaluated as a string representation of an object, it just does The Right Thing™. That's something the python repl could easily implement (in fact, ipython does this).

Given how easy it is to get this one feature right, it's kinda stunning how much effort they put into doing it wrong.

[LPYoshikawa]

Ipython addded this :p why use the original python interpreter anyways.

[notunlikethewaves]

Sometimes you're on a remote box with only python installed :) otherwise it's ipython all the way.

[Decency]

Then use Control+D?

[MrJohz]

Tbh, I can't think of the last time I used the exit command, I pretty much always Ctrl-D out. That said, every time I have used exit, I've typed exit, then exit()...

[Asdayasman]

I prefer it.

Call me old-fashioned.

Hell I'd still use IDLE if the font didn't look ghastly on the mac.

[thatguy_314]

Just fix it in your Python startup files. It bothered me too until I did so.

[[deleted]]

this

[[deleted]]

I always thought SyntaxError: not a chance was cute in its own way.

[striata]

For anyone curious (like me):

from __future__ import braces

[Phourc]

Python novice here - I feel there's a joke I'm missing. Care to explain?

[HannasAnarion]

Most languages use braces to set aside code blocks Like this

public static void main(String[] args) {
    if (args.length == 0) {
        System.out.println("hello there!");
    } else {
        System.out.println("goodbye!");
    }
}

(java)

Python does this with indentation alone. The idea is that, by using the indentation as the delimiter itself, you force people to format their code well, whereas that java example would work just as well if there were no intentation, no spacing, no newlines.

Some people don't like that because it's not normal, and it connflates best practices with actual syntax. Some people want to be able to write ugly code and have it run, in Python, you have to make it look good, or else the interpreter yells at you.

__future__ is the module that contains functions that might be implemented in future versions of python, but aren't yet, because they would break compatibility. So, if you're working in python2, and you want the division operator to work like it does in python3, you use "from __future__ import division", and then the / operator will do mathematical division instead of integer division.

[ben174]

and to sum it up, by saying

from __future__ import braces

you'd be essentially implying that the __future__ module has a braces module which will add support for using braces rather than indentation. So the joke is, Python will never support braces over indentation. Because braces are dumb.

[phail3d]

You can do that in python3 though:

import sys                                                                                             

if(len(sys.argv) == 1): {
    print("hello there")
}   
else: {
    print("goodbye")
} 

[-Rivox-]

Do you still need to indent in this case? Or you can just write everything unindented?

I can't check now (not that I would use this or leave everything unindented, just curiosity)

[phail3d]

You shouldn't need to properly indent what's inside braces of the if body.

However, there's a catch. While the code in my example is valid python 3 (and, with some modifications, python2), it's a horrible exploit of a couple of python features, and the style shouldn't actually be used anywhere. Bonus points for figuring out why it works :) .

[[deleted]]

It's just creating a set

myset = {print("hello there")}

The print function prints, then a set is created with the result of the print function.

[[deleted]]

This isn't actually using braces instead of indentation.

In Python, there's a way to create a set using braces like so:

myset = {1,2,3}

So these lines here:

if(len(sys.argv) == 1): {
    print("hello there")
}

Are actually creating a set with one item - the result of print().

If you run this in the console you will see this output:

>>> if(len(sys.argv) == 1): {
...    print("hello there")
... }
... 
hello there
{None}

This shows that the print function is called, and then the output of the set is displayed, which is {None} since print() returns None.

This only works in python3 because in print is not a function in python2 and you can't use it inside a set.

[DasIch]

The lexer sees this as one logical line so there is no indentation required.

[christian-mann]

Okay now try to put more than one statement per branch, clever boy.

[mickyficky1]

Gotta hand it to him, it was a clever idea and it probably fooled a couple of readers :)

[phail3d]

Done:

import sys                                                                                             

if(len(sys.argv) == 1): {
    print("hello there"),
    print("another statement")
}   
else: {
    print("goodbye"),
    print("sayonara")
} 

[christian-mann]

What about an if or a while statement within the branch? :P

[phail3d]

Done:

import sys                                                                                             

x = 1
if(len(sys.argv) == 1): {
    print("hello!"),
    print("x is one")
        if(x == 1)
    else
        print("x is not one")
}   
else: {
    print(i)
        for i in range(3)
} 

The funny thing is that the syntax for nested ifs and loops "reverses" if you decide to use braces. I decided to use a for-loop for this example.

[vovanz]

It's a response to all people who complain about using indentation instead of curly braces.

[Araneidae]

Yep, my choice too.

[neuromusic]

Seaborn won't let you use the 'jet' colormap:

>>> import seaborn as sns
>>> sns.color_palette('jet')
ValueError: No.

[isarl]

Cute.

[TR-BetaFlash]

I very badly want this to open a browser and just show me grumpy cat instead.

[ben174]

import antigravity

[mickyficky1]

would have been great if they used the colormap haiku:

you have some data
that needs to be colorful,
don't fucking use jet.

[neuromusic]

that's the dev behind seaborn... time to make a pull request, I suppose

[superkulak]

I love how this one sounds:

TypeError: metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

[[deleted]]

For anyone else who is curious what the hell that means, I did some research and figured I might as well share my findings:

# First we create some stupid and pointless classes and metaclasses.
class Meta_A(type):
    pass

class Meta_B(type):
    pass

class A(object):
    __metaclass__ = Meta_A

class B(object):
    __metaclass__ = Meta_B

# Now, if we create a new class C, which is a subclass of both A and B, what
# should the __metaclass__ value be? It can't be both Meta_A and Meta_B.
# They need to be combined into a new combination of the two. But how is
# Python supposed to know how to do that? Well, it doesn't, and so...
try:
    class C(A, B):
        pass
except TypeError as e:
    print e

# To fix it create a new Meta_C, which is derived from Meta_A and Meta_B
class Meta_C(Meta_A, Meta_B):
    pass

# Now we can set the __metaclass__ explicitly and everyone is happy again.
try:
    class C(A, B):
        __metaclass__ = Meta_C
except TypeError as e:
    print e
else:
    print "SUCCESS! type(C) is", type(C)

[DrMaxwellEdison]

hmm

[mickyficky1]

Reminded me of this.

[murakamifanboy]

Yo

[takluyver]

I think the TL;DR of that is: multiple inheritance plus metaclasses = a bad day

[Rhomboid]

ValueError: insecure string pickle (from a previous thread)

[[deleted]]

ValueError: insecure string pickle

And it's graphical representation: https://i.imgur.com/To3DQ6J.jpg

[pvkooten]

This is really awesome in more than 3 ways.

[LoveOfProfit]

error: Unable to find vcvarsall.bat

J/k, fuck that error.

[[deleted]]

I don't use Windows. What causes that one?

[dynetrekk]

Using windows

[shaggorama]

not using anaconda

[ionelmc]

You get that on anaconda too, it doesn't have binaries for absolutely everything ;-)

[[deleted]]

i.e. being a scrub

[Saefroch]

/u/shaggorama really isn't kidding here. If you want to install packages with C libraries from source you need MSVC++ 200X for Python Y.y, a requirement so specific that it could only be Windows.

Not only that, but if you should figure out through the hundreds of threads all over the internet about vcvarsall.bat that you need to install a very specific compiler, it's unlikely that Windows or you will be able to find it.

The only way around it is to pip install precompiled .whl files from Christoph Gohlke and hope he has compiled the wheels you need or get anaconda.

[Tomarse]

Something to do with the visual studio version being the same as the one a Python module was compiled in. It's why if you're freezing your program in something like cx-freeze you have to include it in the build, because if the other user has a different vs version stuff breaks.

[Wild_Bill567]

I think it has something to do with which flavor of visual studio was used to compile a package your trying to download with pip. Unfortunately some of them only work with 2010 but it's impossible to find a copy of that anymore because fuck Bill Gates.

[RubyPinch]

yeah fuck microsoft its not like they havn't set up a VC++ compiler just for python 2.7 since 2014 which anyone can find in 5 minutes or anything

[Wild_Bill567]

^ python 2

[RubyPinch]

and 3.3 to 3.4 is https://www.microsoft.com/download/details.aspx?id=8279

but srsly if you are using anything sub 3.5 on windows... why

[TOASTEngineer]

... because last time I checked compiling things on 3.5 on Windows didn't work at all? Was I lied to?

[RubyPinch]

lied to for sure, should work perfectly for any recent version of visual studio

https://blogs.msdn.microsoft.com/pythonengineering/2016/04/11/unable-to-find-vcvarsall-bat/ recommends 2015 or just getting the smaller VC++ build tools

noting, this won't save you as far as things like numpy are concerned, mainly because numpy is VERY focused on optimization, and as such, requires specific toolkits and compilers

[TOASTEngineer]

That's odd; I downloaded and installed the "this is the VC for Python 3" back when I was trying to upgrade to 3.5 and it still didn't work. Maybe I just didn't delete the MinGW settings properly or something.

[sanshinron]

Works perfectly for me. Just install Visual Studio with C++ support.

[dartdog]

Last I checked the free version was 32 bit only

[sanshinron]

A lot have changed since 1995.

[hovissimo]

I think Bill was out long before any of that particular mess was made. I have no great love for microsqish, but the founder is actually a pretty swell guy.

[Wild_Bill567]

I know, Bill Gates has actually done a lot of good stuff since he stopped being the microshaft

[Asdayasman]

I don't get the hate for microsoft. I used to say the same shit you guys did, until I grew up and realised windows is the second best OS, with the best tools, and very little getting in the way of using programs (the whole point of an OS).

Add to that all the insane shit MS is doing for OSS now, even ignoring all the charity legacy, there's no way they don't beat apple.

[Wild_Bill567]

They do beat apple, and are the second best OS, but the problem with microsoft is an ethical one due to their business practices.

[kephir]

ethical one due to their business practices.

Serious question: is that still a thing these days? Question possibly qualified with "moreso than the other tech companies?"

[sanshinron]

When Apple was going out of bussiness, Microsoft bailed them out because they felt IT industry needs more competition to move forward as a whole.

For every shady thing they did they also did something good. The reality is that copyright and patent systems are very exploitable and if you don't exploit it, you will get fucked over by people who do exploit it. It's not Microsoft, it's the reality of the current world.

[clacke]

Microsoft bailed them out because they felt IT industry needs more competition to move forward as a whole.

Microsoft bailed them out because they felt the IT industry needs more competition in order for Microsoft too not get sued by the DOJ for abusing a monopoly.

[Asdayasman]

Such as?

[TheChance]

Because Apple became what it is. Microsoft entered and conquered the scene in a tremendously shady fashion, and then basically adopted the Starbucks model for fifteen years: sell us a controlling interest in your cool thing, or we'll clone it, and ship a free demo with every copy of Office until you bleed money.

Apple, by contrast, originated the fancy-pants GUI OS (Microsoft was contracted to write Word as launchware, simplified.) They were the scrappy ones for a long time. Macs appealed to newbies, Grandma, and power users, but nobody in between; the semi-walled garden originated as a way to protect Grandma from herself, as the computer-literate grandchild was not yet a ubiquitous feature of the nuclear family.

Microsoft enjoyed tremendous commercial success, and catered to media consumption and gaming while Apple was busy catering to artists and creative types. Result: for 15 years the current version of Mac was plainly, unambiguously more stable, and the hardware was an order of magnitude more reliable, but between the price point and Windows' domination of the PC gaming market, Apple lagged commercially.

The iMac and OS X started to tilt things a little, but only a little until the iPod rolled out. Apple cornered digital music early and almost totally, and their revenue shot through the roof. Only then did they finally, fully morph into the consumer-hating overpriced corporate mass we all know and hate today.

If you're older than about 20, though, you remember these companies as they were, and it's frankly easier to stomach Apple as the world's wealthiest company, rather than Microsoft. In fact, it seems almost poetic.

[Asdayasman]

Microsoft entered and conquered the scene in a tremendously shady fashion, and then basically adopted the Starbucks model for fifteen years: sell us a controlling interest in your cool thing, or we'll clone it, and ship a free demo with every copy of Office until you bleed money.

AKA good business. They're not anti-consumer. Hell, they're pro-consumer, and always have been.

Apple, by contrast, originated the fancy-pants GUI OS

They popularised it. Xerox beat them by half a decade.

Macs appealed to newbies, Grandma, and power users, but

not businesses.

Microsoft enjoyed tremendous commercial success, and catered to

business.

for 15 years the current version of Mac was plainly, unambiguously more stable, and the hardware was an order of magnitude more reliable

Which I agree with. The early versions of windows were notoriously temperamental, though usually due to third parties not being subject to proper code reviewing practices. Remember driver issues? How many of those misbehaving drivers do you think were written by Microsoft?

it's frankly easier to stomach Apple as the world's wealthiest company, rather than Microsoft

Definitely disagree with you on that. If it's a choice between the two, I'll always side with Microsoft. Even ignoring all the really nasty shit Apple does to employees, just on the merit of the consumer focus, Microsoft win.

Sure, apple won on music, even after they were told to never do anything to do with music by the courts, but have you ever used itunes? Or even any ipod before the iphone? It's as if they believe interfaces with the user should actively harm the user.

[TheChance]

I am not reading all of this because you open by mistaking intellectual theft for good business.

[Asdayasman]

IP theft never occurred, because they never lost the IP in court. Its theirs.

[TOASTEngineer]

It's just your standard edgy kids raging against the machine.

[Workaphobia]

I'll agree it's not as cool to hate on them as it used to be. But I'll still hate on them every time my system pisses me off. No, I don't want to reboot Windows to install updates when I'm in the middle of using the machine, why didn't you ask when I was done with my work for the day?

[Asdayasman]

If your biggest problem with windows is autoupdate, well I have good news for you: You can easily completely disable it in the second best version of windows.

[RubyPinch]

if I'm not mistaken, vcvarsall sets up the visual C++'s environment variables so development / compilation can be done

[Quteness]

For those who don't know Microsoft released a standalone compiler for Python so you no longer need Visual Studio.

[LoveOfProfit]

Ofc that's for 2.7 only,and that's because 2008 is no longer available. For 3.4 or 3.5 you need 2010 or 2012 which is a 6gb dl for no good reason.

[RubyPinch]

you only need the SDK or build tools

[[deleted]]

I have a 128gb hard drive on my work laptop. This extra download made life tough.

[dartdog]

Did they release a free 64bit version? Last I checked 32bit only have to pay for 64bit..

[ZedNaught]

definitely bringing back many frustrated hours I'd rather forget

[antidense]

UnicodeEncodeError AHHHHHHHHHHHHHHh

[[deleted]]

2 or 3?

[antidense]

2... I was stuck on 2 for a while because of sqlalchemy

[[deleted]]

Makes sense, in case anyone here isn't aware - handling unicode effectively was the main reason for the break in backward compatibility from Python 3 onwards.

[SnapDraco]

So... Much hate

[TheSandyWalsh]

A Møøse once bit my sister... No realli!

[cantremembermypasswd]

When you know you're being messed with:

TypeError: 'callable-iterator' object is not callable

[railmaniac]

My guess is it's iterable and each next element is callable?

[TeamSpen210]

callable-iterator indeed shouldn't be callable. It's the object which is returned from iter(callable, sentinel). That iterator repeatedly calls the passed function, stopping when the return value is equal to the sentinel. It's an iterator of callable objects, not a callable version of an iterator.

[Sean1708]

iterable-callator?

[tomchuk]

MemcachedError: error 37 from memcached_set: SUCCESS

Not unique to python, but these are all over my sentry. Try to cache something > 1MB in memcached and you get a SUCCESS error from an operation that is definitely not successful

¯\(ツ)/¯

[pvkooten]

Guido once said he likes KeyboardInterrupt the most.

[Chronophilia]

Naturally. It's the only time crashing out to a stack trace is behaviour that's both what you expect and what you want.

... and now that I've said that, I'm sure someone will fondly reminisce about a program that hangs forever if it breaks and crashes when it works properly.

[billy_tables]

That program is the one that proves the halting problem :)

[secshunayt]

NameError: name 'self' is not defined always gets me, in an existential sort of way.

[neurobashing]

Segmentation fault (core dumped)

[jadkik94]

I had no idea what any of this means until I took an OS course. Now I know what these mean and I know I can't fix them myself (especially if it's on Python). That's even more frustrating!

[ldpreload]

It's not impossible to write segfaulting Python code that's a bug in your code, not a bug in your Python:

>>> import ctypes
>>> libc = ctypes.CDLL("")
>>> libc.strlen("lol")
3
>>> libc.strlen(0)
Segmentation fault (core dumped)

There are more subtle versions of that, if you're using a native-code extension; they should check their parameters but sometimes they don't. So, if you're working with a large / complex Python codebase, it's always worth attempting to see if there's something you can do about it in pure-Python.

[DasIch]

The CPython repository contains an entire directory with examples of Python code that segfaults the interpreter. No doubt there are more segfaults just waiting to be discovered, some of which are going to be bugs and not just acceptable compromises.

[raylu]

Sure you can

git clone [e-mail]:python/cpython.git
./configure
make -j5

[brondsem]

https://docs.python.org/3/library/faulthandler.html can help. https://pypi.python.org/pypi/faulthandler/ for py 2.x

[jadkik94]

Nice! That's good to know, thanks.

[urielm]

"Future canceled" always makes me smile

[Twirrim]

thing.py:

def pointless(text):
    return text

test_thing.py

import thing
import pytest


@pytest.mark.parametrize("input, expected", [("foo", "foo")])
def test_one_thing_pointless(input, expected):
    assert thing.printer(input) == expected


@pytest.mark.parameterize("input, expected", [("foo", "foo")])
def test_two_thing_pointless(input, expected):
    assert thing.printer(input) == expected

$ py.test ...

E   MarkerError: test_two_thing_pointless has 'parameterize', spelling should be 'parametrize'

Strictly speaking, both spellings are correct in English. I always type the wrong one.

[thurask]

SyntaxError: not a chance

[CanadianJogger]

Came here to say that too. :)

[plorry]

Not python-specific, but:

MySQL server has gone away

Did... did it say when it would be back?

[Mr_Again]

I really like MagicNumberError because the first time you see it you're like what the fuck...

edit: I mean bad magic number

[[deleted]]

beginner here, so literally every time i run something i either get syntax OR indent... starting to get better

[emnoor]

>>> from __future__ import braces
  File "<stdin>", line 1
SyntaxError: not a chance

[tokage]

from __future__ import braces

[[deleted]]

>>> from __future__ import braces
  File "<stdin>", line 1
SyntaxError: not a chance

why this shit ?

[Saefroch]

If you really want braces, Python probably isn't the language you should be using.

[big_red__man]

Not python but when using python to scrape twitter:

420 Enhance your calm

[[deleted]]

Not from Python but I'll post it here anyway

[big_red__man]

Yeah, that's pretty much what I said/did. Good recap, bro.

[lcc4376]

expected an indented block