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16:00
>>> a = "the quick brown fox"
>>> b = a.split()
>>> print(b)
['the', 'quick', 'brown', 'fox']
user228700
Hmm, and what about if I want to initiate a list with values that the user inputs? As I understand it, you can't use the for loop to do this, as you would with arrays in C++...
user228700
@JohnRennie Yes, thanks so much! :-)
The quickest way to learn these things is to try it ...
Anonymous
208
Q: Create an empty list in python with certain size

Ronaldinho Learn CodingI want to create an empty list (or whatever is the best way) that can hold 10 elements. After that I want to assign values in that list, for example this is supposed to display 0 to 9: s1 = list(); for i in range(0,9): s1[i] = i print s1 But when I run this code, it generates an error or...

user228700
I've tried it before, using loops to initiate an empty list, but it's really weird. So even though lists are mutable, you can't say list1[i]=int(input("Input a number"))
Anonymous
16:01
SO has answers to almost all your question ;)
@Kaumudi.H do you mean take inputs from the user one at a time and concatenate them into a list?
user228700
Yepp. Hmm, so I gotta use the append function, apparently, in loops but not when I am saying something like list[1]='a'...
@Kaumudi.H if you have a list with some length N you can use mylist[i] = xxx for any value of i < N
But you can't create a list using that syntax.
user228700
Right, I can modify an existing list, but can't create one like that.
Yes. Because the ith element of the list doesn't exist until you create it, and you can't modify the value of something that doesn't exist.
user228700
16:09
Right. Gotcha! Thanks! :-D
oh no latex
why are you doing this to me
I loved you like a brother
@EmilioPisanty Doing my usual quick scan back through stuff I missed, and I saw your discussion with giS about a potential expert level physics Q&A site.
@Kaumudi.H so for example this is legal:
>>> for i in range(0,9):
...     a.append(i)
...
>>> print a
[0, 1, 2, 3, 4, 5, 6, 7, 8]

>>> for i in range(0,9):
...     a[i] = i*2
...
>>> print a
[0, 2, 4, 6, 8, 10, 12, 14, 16]
TeX thinks this is on a new page
I'd like to express my thanks for your continuing efforts to make Physics SE interesting enough to attract experts here.
6
You've been doing something concrete (and not easy) on a matter that other people only talk about.
user228700
16:11
@JohnRennie Yes, I understand!
(For those you who don't know what I am on about: check out Emilio's questions tab.‌​)
hahaaaaaa fixed it
I am the TeX hacker
user228700
Ugh, working with Python after having done C++ is a pain in the neck.
@Kaumudi.H In what way? I'm primarily a c++ hacker, and I like python.
Anonymous
I'm learning C and Python simultaneously (and had Java in school). Often confuses the hell out of me. SO always comes to the rescue. :)
Anonymous
16:17
Python and C++ is a better combination tbh
user228700
Just the fact that Python uses an interpreter and C++ a compiler. It's...weird, when statements just give outputs without invoking the "print" function.
Anonymous
Both are high level languages
Three is nothing fundamental about a compiler/interpreter difference. I've used a c++ interpreter (Well, without the ability to do templates in the interpreter, though it would talk to external libraries compiled from template code).
I like to think of REPLs as a kind of debugging aid rather that a fundamentally different kind of thing.
Anonymous
Well Python does use a compiler...to convert .py to bytecode...
user228700
Well, I guess it's just annoying to me just 'cause I'm learning to give answers on a test :-/
Anonymous
16:21
@dmckee That is very true
The REPL is just capturing and informing you of the result of expressions as you go along.
kind of like step; print [something] in gdb, but it happens automatically.
I really need someone to take math chats offline for at least a week, cannot stand on having 3 vampires on at the same time
there's an ignore button...
2
@BalarkaSen explain these ODEs to me
which ode
ODE to joy
16:27
I get crazy results with an aggressive control scheme
@BalarkaSen just f***ing crane?
when you have a 7 equation system your best bet is the computer
@BalarkaSen I am doing the computer
user228700
16:31
@Balarka: Background music to revision:
but I am getting very unphysical results
user228700
user228700
x'D
user228700
Repeated 32 times!
16:33
I like the version with Hitler in the music video
you like something with Hitler in it?
Perhaps @yuggib could help.
what?
@0celo7 Sure. I like the Downfall meme, for example
Explain
13 mins ago, by 0celo7
@BalarkaSen this one https://i.gyazo.com/36f1751455e7a9a90290ad2ec47db769.png
16:42
@dmckee gee, thanks a bunch =)
2
16:53
@dmckee Congrats :)
I am not a black hole expert, not sure how good these coordinate invariants are
@Secret That moment a paper sounds really interesting but you don't know enough to validate it...
Margaret has gained a family since this morning! #Oxford #uksnow
@SirCumference Thanks. She's five months and a few days old now: strongly opinionated, social, and beginning to be mobile. I'm gaining weight and losing hair and happy as can be.
user228700
@Blue: If you have the tiniest of interest in this stuff: apparently Virat and Anushka just got married.
16:56
@dmckee Oh...I somehow thought that was posted 4 days ago...
But that's great to hear
Sid
Sid
@Kaumudi.H does anyone apart from the media cares?
@Kaumudi since when are you interested in gossip pseudonews about celebrity scumbags?
user228700
Apparently, yeah; I found out about it 'cause my friends (yeah, plural) posted a status about it.
Sid
Sid
@dmckee How does she express her opinions? Crying really hard?
@dmckee how can a baby be opinionated
16:58
Inquiring minds want to know :P
user228700
@BalarkaSen Eh, I don't follow this stuff in the slightest-just posting 'cause it'll be everywhere soon enough and like I said, I only got to know about this 'cause my friends posted a status about it on WhatsApp.
@Sid That and reaching for things, batting stuff away, smiling when you do something she likes, giggling if it is extra fun, gaping her mouth if she is hungry, turning her head if you offer food she doesn't want and on an on. Mostly non-verbal stuff.
@BalarkaSen Scumbags?
yeh capitalist scumbags
17:01
If I can't call homophobes idiots I don't think you should be able to call random people scumbags.
@dmckee what is the moderators' opinion on this
I don't speak for moderator in the plural. I'd suggest reining in that language a little.
Dec 6 at 18:42, by John Rennie
For the record, whoever flagged that, homophobia is bigotted, small minded and stupid behaviour and Ryan was quite correct to call homophobes idiots.
I agreed with the idiot comment
Dec 6 at 18:44, by ACuriousMind
@JohnRennie I'm around. Just for the record, don't call people idiots even when it's true, though I've reversed the suspension.
Being a celebrity as such doesn't reflect badly on a person. Even being famous for being famous isn't a crime.
17:04
> even when it's true
+1
Though it is inexplicable to me. People are strange.
according to Stack Exchange Laws, Hitler wasn't an idiot
@0celo7 I'd say "sociopath" rather than "idiot"
Hitler knew Jackson for gosh sakes
@SirCumference Oh, talking about mental conditions is even worse!!!!
17:05
@0celo7 That kind of passive aggressive twaddle does not reflect well on you.
@dmckee According to Soviet Russia, it is.
I am making a far left standpoint here
@SirCumference I suspect johnrennie and slereah may knew something about it, as it was on arxiv for two years
and both of them like to work with various spacetime metrics including black holes
@Secret Welp, pinging @JohnRennie and @Slereah in case they're interested
@dmckee Not passive aggressive, just amusing
@bolbteppa that's good but not as good as Hilter and clopen sets
17:07
I love that video ^^
I want one with algebraic topology
memory error D:
There's also a meta-video about Bruno Ganz on being memed
I don't think I've seen this one haha
@BalarkaSen yeah, that one is tough
it took me a while to realize that the interview is going on and on about whatever else
17:09
Same
Anonymous
@Kaumudi.H "Just"? My classmates already made memes about it hours ago
user228700
x'D Nice!
Indian memes about Indian celebrities
I shouldn't be surprised these things exist, but still
'friendly set'
17:11
aka a set with $C^\infty$ boundary
@0celo7 it boils my blood to see them
@BalarkaSen ...why?
boils it in the finest communist sense
Anonymous
are you a self-hating Indian?
17:13
I am not racist
I am hating on capitalism
user228700
@Blue Lol.
@BalarkaSen I can't take you seriously
lol:
> "Who the hell came up with these terms?" -- actually, a German Jew (Georg Cantor) .
> David Snyder So he would indeed have him hunted down and killed by the SS.
how is $C^\infty$ defined on sets
17:18
it's not; what he means is that the boundary is a C^infty submanifold
does that make the set a manifold
an open set is always a submanifold
it's the boundary that's usually not. in this case you say it is, and a nice one too
hmmm
An open set can always be given manifold structure? That's not obvious to me..o.o
An open set of R^n, yes
Every point admits a ball neighborhood
of R^n...where was R mentioned...I must have missed too much of the conversation lol
17:20
it was implied
God "clopen"
the lack of rigor is terrible, I hope it will last
I was thinking like (1,2,3) how u turn that into a manifold...
D:
@enumaris that's a zero-manifold
three points
in space
17:21
haha
floating among nothingness
that doesn't make a manifold tho
Is the space separable or
since u can't map it into open balls can u
@enumaris It does. It's locally homeomorphic to R^0
17:22
@enumaris of course it does
a 0-ball is a point
It's a rather dumb manifold
@BalarkaSen have you learned Morse theory yet?
I need someone to check my argument
only superficially
R^0...hmmm
@BalarkaSen Ok it's a kind of tricky argument using the Morse index
nvm then
17:24
mmkay
I guess if u allow mapping to R^0 then that works...
@0celo7 do you want to briefly explain Morse theory like it was multivariable calculus
tbh closed set sounds more (insert suitable word) than an open set. Are there actually closed sets that contain boundary points that are not limit points
@bolbteppa no
@bolb second derivative test
17:25
From browsing his original paper that's the way he framed it
that's how people think about calculus of variations, yes
Vaguely remember he gives a motivation for applying the SDT globally, no functionals just calculus
but I need a result on the cut locus, which is a kind of tricky object
that's the critical set of exp?
no that's the conjugate locus
17:27
oh
cut locus is that + some more points
@BalarkaSen the practical thing is that the cut locus is where the distance function isn't $C^\infty$
and I'm working with distance functions so I have to care about that
painful
17:56
So the morse lemma seems to be generalizing the idea of a function being concave up or concave down, i.e. being an upward pointing or downward pointing parabola, near a critical point, or a real-valued function of two variables being a saddle etc... near a critical point, by factoring it into a sum of squares where the pattern in the signs (index) tells you what kind of surface it is?
Seems like the proof is just shifting to get rid of the $F(x_0)$ point, then diagonalizing the quadratic form, then proving the law of inertia applies to it or something like that?
Morse lemma is a second order generalization of the inverse function theorem
It tells you upto second order what your manifold looks like at the nondegenerate critical point
(namely, like $\sum \pm x_i^2$)
@BalarkaSen wait did you recommend me bott & tu?
or was it something else
I recommended Guillemin-Pollack
ah
Bott-Tu is a hard book. I think there is a book by Tu on intro to diff top
18:01
i remember seeing a manifolds book
by tu
yeah that
I think that doesn't take much background
you should pick it up
uhhh
and GP?
it doesn't take much background either?
i thought it did because rye was reading it last year
That's interesting, so I guess once you're done analyzing points with non-zero derivative (IFT), you next analyze points with zero derivative and end up with the Morse lemma trying to mimic the IFT in some sense, but it seems like it is copying the whole concave up/down thing from baby calculus more directly than the IFT?
3
Q: Proof of the Morse Lemma in dimension 1

VrouvrouThis is the Morse lemma in dimension1 : Let $M$ be a smooth $1$-manifold and $f: M \longrightarrow \Bbb R$ be a smooth function. Suppose $p$ is a non-degenerate critical point of $f$. Then there exists a local coordinate system $(y^1)$ in a neighborhood $U \subset M$ of $p$ with $y^1(p)...

oh well let's keep things interesting
and read a book without background
i love doing that
getting this multi-processing to work is pretty hard it seems
18:11
I read GP two years ago
It doesn't require lots of background but it's a thought-provoking book
ya i'm considering saving it for a lil later
what's a nice book that draws from a lot of areas
wtf, half the time I get a filenotfound error, half the time the thing actually runs
with 0 change to the source code
Berger, "Nonlinearity and Functional Analysis"
baffling...
@0celo7 reading the ToC it looks specialized
18:15
Not at all
like for someone who cares about that stuff
seems like a pretty random thing to learn for me
why is it important?
everyone should care about nonlinear functional analysis
@ooolb lots of nonlinear PDEs out there
sure but
i want something more immediately related to QFT/GR
immediately like at physicist level
those are two subjects which are degenerate at physicist level
i'm working on it
i think geometry is a good place to start
to wash away the "degeneracy"
18:21
wut
i'm playing along with it
Anonymous
@ooolb What type of physics do you do? I never asked...
nothing right now
somebody save me from this multiprocessing fiasco
i did qft and ehhh gr some long time ago
long long time back
Anonymous
18:23
So you're a physics undergrad?
yes
Anonymous
Nice
not really
@enumaris I can give you a problem to work on instead.
@Blue math/phys
Anonymous
18:24
@ooolb Ic...cool stuff
@ooolb just read Reed and Simon
ok i'll reed read and simon
ha
I ain't no maths person
fun
@0celo7 alright
what background do i need?
it's even cheaper now that's weird
I would suggest advanced calculus and measure theory
Anonymous
18:26
I started Reed-Simon without any background. Just use youtube videos along with it or ask balarka for help :P
i'd prefer not to get help right now
Anonymous
Will get back to reading it soon after this exams are over
Why would you ask Balarka about functional analysis?
i need to build character
That actually hurts me.
18:27
@0celo7 i wouldn't
@Blue likes to ignorantly offend people and i don't think he even realizes
Anonymous
I have trouble taking you seriously @0celo7 :P
What does that even mean?
like the fact that you just said that @Blue is enough evidence for me to not want to read anything you post in this chat
combined with other things from before
user228700
@Blue: You around?
Anonymous
@Kaumudi.H Ya
user228700
18:29
:-) Great! Have you studied Classes and Objects in Python?
Anonymous
Little bit...but I got a test tomorrow...not sure if I'll be able to help much
Anonymous
If it's a short question go ahead...
user228700
It's OK, I only have one question.
In any case @ooolb unless you're a complete genius it's impossible to read Reed and Simon without background.
measure theory...
18:30
I figured and I'd rather spend the time right now doing something more productive
And you're missing out on a lot of stuff if you do that
user228700
What is the syntax to declare attributes within a class? Must we use self?
@enumaris what about it?
are you trying to be rigorous with the crazy measures you find in the path integral formulation of QFT?
@enumaris No
18:30
@enumaris me?
it will only lead to tears
You need to be rigorous with Lebesgue measure and spectral measures
and heartbreak
And other measures
Screw path integrals
to be honest i don't really understand how rigour fits into physics
18:31
First of all it's spelled rigor
hey man, path integrals are cool
so what if they are all formally infinite
@0celo7 murican
lmao but i'm saying that
right now i'm on a road to appreciating it
in physics
Maybe it doesn't, but physics isn't all that interesting
Anonymous
@Kaumudi.H This has a detailed discussion: toptal.com/python/…
i don't study anything because it's interesting
idgaf actually
like 5% curiosity the rest is for synesthetic reasons
18:34
@ooolb that's completely wrong
which part
you need to find what interests you 100%
and do that
uhm
sounds like it's not math or physics
it is
because other things
it's like 0.5%
or less
18:35
well my usual solution for that situation is not chat friendly
but you know what it is
i don't actually
hint?
lmao
dude you're not getting it
@BalarkaSen are you there?
I don't particularly believe in having to suffer through a tortured existence
whoah my dude
i like physics/math
it's the only thing i like
i'm just saying i don't like it because i find it interesting
50% of it is interest
the rest is how it looks in my mind when i do it
i like the feeling
Anonymous
...
you're high
18:40
lol.....
Anonymous
@ooolb Sounds like something a masochist would say.
user228700
I looked at the Python Documentation and seem to have understood it for the most part. Thanks anyway! :-) Good luck for the exam tomorrow!
user228700
@Blue: I'm so sorry! My connection died :-/
@Blue explain?
Anonymous
@Kaumudi.H All the best
18:41
because what you just said makes no sense
@0celo7 urggg i did not ever do drugs before
@ooolb before today?
user228700
@0celo7 @Balarka would disagree :-P
no
aaaaaaaaaaaaaaa
tbh though!
i'd totally be down to do drugs
but
18:43
@Kaumudi.H Balarka doesn't believe in horable ritualistic suicide? I'm surprised.
idk where to go
to find some
Anonymous
@ooolb Come to my place. I'll get you cheap drugs
no i don't want laced shit
why the fock would i go to india to do drugs
@ooolb because cheap
Anonymous
@ooolb Great pricing
18:44
and fake
if i ask around i could probably get some xans in 3 hours from now
@ooolb do it and report back
but i don't really want to
Anonymous
Post a video of yourself as proof.
18:46
@DavidZ I got pretty close to getting the multi-processing to work (required a few more tweaks) but I've run into a "End of File" error that I don't know how to deal with D:
with today's newspaper
Anonymous
@Keepthesemind lol
send me your energy!
this isn't real
Poppin xannies
18:47
i was roleplaying someone who was for 5 minutes ironically interested in doing drugs and thought they were funny in doing so
@ooolb please don't do that
it's just annoying
sorry
where are the computer wizzes...I need help getting rid of this end of file error lol
Anonymous
sleeping
18:54
:(
@enumaris Well, "getting rid of this end of file error" is so vague I can't tell whether I can help you or not :P
it involves multi-processing in python
make bigger file
I don't think the error actually comes from an end of file
lol
cus I'm grabbing chunks of the file, and I never grab the end chunks

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