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Escape sequences in vim (neovim) Python feedkeys

I want to be able to control vim/neovim on a per-key basis with python scripting. There is a function called feedkeys in the python vim module (vim.feedkeys) that is nearly what I want. However, I haven't been able to figure out how to send things like function keys, arrow keys, pgup, pgdown etc as it always takes my strings completely literally.
As per the documentation for vim's feedkeys (vimscript version, not python)
feedkeys("\<CR>") simulates pressing of the <Enter> key. But feedkeys('\<CR>') pushes 5 characters.
Things I've tried with the python counterpart that haven't worked (note, <CR> is just an example; I know I can use \n for that. Nonetheless, this should simulate an enter keypress):
vim.feedkeys("\<CR>")
vim.feedkeys("<CR>")
vim.feedkeys("\<CR\>")
vim.call("feedkeys", "\<CR>")
vim.call("feedkeys", '"\<CR>"')
All of these were interpreted literally. I want to do something like
vim.feedkeys("\<F5>") etc. Any ideas?

This isn't ideal, but it solves my issue well enough:
vim.command('call feedkeys("\<F5>")')
In case this is useful to anyone, I've written a general function that will handle the \<> escapes as well as double-quotes:
def fkeys(text):
firstsub = True
for sub in text.split('"'):
if firstsub:
firstsub = False
else:
vim.feedkeys('"')
vim.command(f'call feedkeys("{sub}")')

Sorry for being Captain Obvious, but it doesn't work, because Python is not VimScript.
See :h nvim_replace_termcodes() and :h nvim_feedkeys() for a complete example. In case of <CR>, simply byte value of 13 will do.

You don't, because the interpretation of something like "\<CR>" is a function of VimL string literals. In other words, feedkeys("\<CR>") is the same thing as (probably) feedkeys("\x0d") — the function doesn't see the difference, the interpretation happens at a source code level. Naturally, Python doesn't have the same feature in the same way.
If you don't want to figure out what the escape sequence is for F5 and code it into your Python script, perhaps you could use vim.eval() to eval a VimL expression, e.g. vim.eval(r'feedkeys("\<F5>")').

Is there something similar to __END__ of perl in python? [duplicate]

Am I correct in thinking that that Python doesn't have a direct equivalent for Perl's __END__?
print "Perl...\n";
__END__
End of code. I can put anything I want here.
One thought that occurred to me was to use a triple-quoted string. Is there a better way to achieve this in Python?
print "Python..."
"""
End of code. I can put anything I want here.
"""

The __END__ block in perl dates from a time when programmers had to work with data from the outside world and liked to keep examples of it in the program itself.
Hard to imagine I know.
It was useful for example if you had a moving target like a hardware log file with mutating messages due to firmware updates where you wanted to compare old and new versions of the line or keep notes not strictly related to the programs operations ("Code seems slow on day x of month every month") or as mentioned above a reference set of data to run the program against. Telcos are an example of an industry where this was a frequent requirement.
Lastly Python's cult like restrictiveness seems to have a real and tiresome effect on the mindset of its advocates, if your only response to a question is "Why would you want to that when you could do X?" when X is not as useful please keep quiet++.

The triple-quote form you suggested will still create a python string, whereas Perl's parser simply ignores anything after __END__. You can't write:
"""
I can put anything in here...
Anything!
"""
import os
os.system("rm -rf /")
Comments are more suitable in my opinion.
#__END__
#Whatever I write here will be ignored
#Woohoo !

What you're asking for does not exist.
Proof: http://www.mail-archive.com/python-list#python.org/msg156396.html
A simple solution is to escape any " as \" and do a normal multi line string -- see official docs: http://docs.python.org/tutorial/introduction.html#strings
( Also, atexit doesn't work: http://www.mail-archive.com/python-list#python.org/msg156364.html )

Hm, what about sys.exit(0) ? (assuming you do import sys above it, of course)
As to why it would useful, sometimes I sit down to do a substantial rewrite of something and want to mark my "good up to this point" place.
By using sys.exit(0) in a temporary manner, I know nothing below that point will get executed, therefore if there's a problem (e.g., server error) I know it had to be above that point.
I like it slightly better than commenting out the rest of the file, just because there are more chances to make a mistake and uncomment something (stray key press at beginning of line), and also because it seems better to insert 1 line (which will later be removed), than to modify X-many lines which will then have to be un-modified later.
But yeah, this is splitting hairs; commenting works great too... assuming your editor supports easily commenting out a region, of course; if not, sys.exit(0) all the way!

I use __END__ all the time for multiples of the reasons given. I've been doing it for so long now that I put it (usually preceded by an exit('0');), along with BEGIN {} / END{} routines, in by force-of-habit. It is a shame that Python doesn't have an equivalent, but I just comment-out the lines at the bottom: extraneous, but that's about what you get with one way to rule them all languages.

Python does not have a direct equivalent to this.
Why do you want it? It doesn't sound like a really great thing to have when there are more consistent ways like putting the text at the end as comments (that's how we include arbitrary text in Python source files. Triple quoted strings are for making multi-line strings, not for non-code-related text.)
Your editor should be able to make using many lines of comments easy for you.

How to let pyflakes ignore some errors?

I am using SublimePythonIDE which is using pyflakes.
There are some errors that I would like it to ignore like:
(E501) line too long
(E101) indentation contains mixed spaces and tabs
What is the easiest way to do that?

Configuring a plugin in Sublime almost always uses the same procedure: Click on Preferences -> Package Settings -> Plugin Name -> Settings-Default to open the (surprise surprise) default settings. This file generally contains all the possible settings for the plugin, usually along with comments explaining what each one does. This file cannot be modified, so to customize any settings you open Preferences -> Package Settings -> Plugin Name -> Settings-User. I usually copy the entire contents of the default settings into the user file, then customize as desired, then save and close.
In the case of this particular plugin, while it does use pyflakes (as advertised), it also makes use of pep8, a style checker that makes use of the very same PEP-8 official Python style guide I mentioned in the comments. This knowledge is useful because pyflakes does not make use of specific error codes, while pep8 does.
So, upon examination of the plugin's settings file, we find a "pep8_ignore" option as well as a "pyflakes_ignore" one. Since the error codes are coming from pep8, we'll use that setting:
"pep8_ignore": [ "E501", // line too long
"E303", // too many blank lines (3)
"E402" // module level import not at top of file
]
Please note that codes E121, E123, E126, E133, E226, E241, E242, and E704 are ignored by default because they are not rules unanimously accepted, and PEP 8 does not enforce them.
Regarding long lines:
Sometimes, long lines are unavoidable. PEP-8's recommendation of 79-character lines is based in ancient history when terminal monitors only had 80 character-wide screens, but it continues to this day for several reasons: it's backwards-compatible with old code, some equipment is still being used with those limitations, it looks good, it makes it easier on wider displays to have multiple files open side-by-side, and it is readable (something that you should always be keeping in mind when coding). If you prefer to have a 90- or 100-character limit, that's fine (if your team/project agrees with it), but use it consistently, and be aware that others may use different values. If you'd like to set pep8 to a larger value than its default of 80, just modify the "pep8_max_line_length" setting.
There are many ways to either decrease the character count of lines to stay within the limit, or split long lines into multiple shorter ones. In the case of your example in the comments:
flag, message = FacebookUserController.AddFBUserToDB(iOSUserId, fburl, fbsecret, code)
you can do a couple of things:
# shorten the module/class name
fbuc = FacebookUserController
# or
import FacebookUserController as fbuc
flag, message = fbuc.AddFBUserToDB(iOSUserId, fburl, fbsecret, code)
# or eliminate it all together
from FacebookUserController import AddFBUserToDB
flag, message = AddFBUserToDB(iOSUserId, fburl, fbsecret, code)
# split the function's arguments onto separate lines
flag, message = FacebookUserController.AddFBUserToDB(iOSUserId,
fburl,
fbsecret,
code)
# There are multiple ways of doing this, just make sure the subsequent
# line(s) are indented. You don't need to escape newlines inside of
# braces, brackets, and parentheses, but you do need to outside of them.

As others suggest, possibly heed the warnings. But in those cases where you can't, you can add # NOQA to the end offending lines. Note the two spaces before the # as that too is a style thing that will be complained about.
And if pyflakes is wrapped in flake8 that allows ignoring by specific errors.
For example in a file in the project put or add to tox.ini:
[flake8]
exclude = .tox,./build
filename = *.py
ignore = E501,E101
This is possibly a duplicate with How do I get Pyflakes to ignore a statement?

Python indentation in "empty lines"

Which is preferred ("." indicating whitespace)?
A)
def foo():
x = 1
y = 2
....
if True:
bar()
B)
def foo():
x = 1
y = 2
if True:
bar()
My intuition would be B (that's also what vim does for me), but I see people using A) all the time. Is it just because most of the editors out there are broken?

If you use A, you could copy paste your block in python shell, B will get unexpected indentation error.

The PEP 8 does not seem to be clear on this issue, although the statements about "blank lines" could be interpreted in favor of B. The PEP 8 style-checker (pep8.py) prefers B and warns if you use A; however, both variations are legal. My own view is that since Python will successfully interpret the code in either case that this doesn't really matter, and trying to enforce it would be a lot of work for very little gain. I suppose if you are very adamantly in favor of one or the other you could automatically convert the one to the other. Trying to fix all such lines manually, though, would be a huge undertaking and really not worth the effort, IMHO.

Adding proper indentation to blank lines (style A in the question) vastly improves code readability with display whitespace enabled because it makes it easier to see whether code after a blank line is part of the same indentation block or not.
For a language like Python, where there is no end statement or close bracket, I'm surprised this is not part of PEP. Editing Python with display whitespace on is strongly recommended, to avoid both trailing whitespace and mixed indentation.
Compare reading the following:
A)
def foo():
....x = 1
....y = 2
....
....if True:
........bar()
B)
def foo():
....x = 1
....y = 2
....if True:
........bar()
In A, it is far clearer that the last two lines are part of foo. This is even more useful at higher indentation levels.

That empty line belongs to foo(), so I would consider A to be the most natural. But I guess it's just a matter of opinion.

TextMate breaks block collapsing if you use B, and I prefer A anyway since it's more "logical".

My experience in open-source development is that one should never leave whitespace inside blank lines. Also one should never leave trailing white-space.
It's a matter of coding etiquette.

I wouldn't necessarily call the first example "broken", because I know some people hate it when the cursor "jumps back" when moving the cursor up or down in code. E.g. Visual Studio (at least 2008) automatically prevents this from happening without using any whitespace characters on those lines.

B is preferred - i.e. no indentation. PEP 8 says:
Avoid trailing whitespace anywhere. Because it's usually invisible, it can be confusing: e.g. a backslash followed by a space and a newline does not count as a line continuation marker. Some editors don't preserve it and many projects (like CPython itself) have pre-commit hooks that reject it.

Emacs does B) for me, but I really don't think it matters. A) means that you can add in a line at the correct indentation without any tabbing.

vi implicitly discourages the behaviour in A because the {/} navigations no longer work as expected. git explicitly discourages it by highlighting it in red when you run git diff. I would also argue that if a line contains spaces it is not a blank line.
For that reason I strongly prefer B. There is nothing worse than expecting to skip six or so lines up with the { motion and ending up at the top of a class def.

Is there a way to convert indentation in Python code to braces?

I am a totally blind programmer who would like to learn Python. Unfortunately the fact that code blocks are represented with different levels of indentation is a major stumbling block. I was wondering if there were any tools available that would allow me to write code using braces or some other code block delimiter and then convert that format into a properly indented representation that the Python interpreter could use?

There's a solution to your problem that is distributed with python itself. pindent.py, it's located in the Tools\Scripts directory in a windows install (my path to it is C:\Python25\Tools\Scripts), it looks like you'd have to grab it from svn.python.org if you are running on Linux or OSX.
It adds comments when blocks are closed, or can properly indent code if comments are put in. Here's an example of the code outputted by pindent with the command:
pindent.py -c myfile.py
def foobar(a, b):
if a == b:
a = a+1
elif a < b:
b = b-1
if b > a: a = a-1
# end if
else:
print 'oops!'
# end if
# end def foobar
Where the original myfile.py was:
def foobar(a, b):
if a == b:
a = a+1
elif a < b:
b = b-1
if b > a: a = a-1
else:
print 'oops!'
You can also use pindent.py -r to insert the correct indentation based on comments (read the header of pindent.py for details), this should allow you to code in python without worrying about indentation.
For example, running pindent.py -r myfile.py will convert the following code in myfile.py into the same properly indented (and also commented) code as produced by the pindent.py -c example above:
def foobar(a, b):
if a == b:
a = a+1
elif a < b:
b = b-1
if b > a: a = a-1
# end if
else:
print 'oops!'
# end if
# end def foobar
I'd be interested to learn what solution you end up using, if you require any further assistance, please comment on this post and I'll try to help.

I personally doubt that there currently is at the moment, as a lot of the Python afficionados love the fact that Python is this way, whitespace delimited.
I've never actually thought about that as an accessibility issue however. Maybe it's something to put forward as a bug report to Python?
I'd assume that you use a screen reader here however for the output? So the tabs would seem "invisible" to you? With a Braille output, it might be easier to read, but I can understand exactly how confusing this could be.
In fact, this is very interesting to me. I wish that I knew enough to be able to write an app that will do this for you.
I think it's definately something that I'll put in a bug report for, unless you've already done so yourself, or want to.
Edit: Also, as noted by John Millikin There is also PyBraces Which might be a viable solution to you, and may be possible to be hacked together dependant on your coding skills to be exactly what you need (and I hope that if that's the case, you release it out for others like yourself to use)
Edit 2: I've just reported this to the python bug tracker

Although I am not blind, I have heard good things about Emacspeak. They've had a Python mode since their 8.0 release in 1998 (they seem to be up to release 28.0!). Definitely worth checking out.

You should be able to configure your editor to speak the tabs and spaces -- I know it's possible to display whitespace in most editors, so there must be an accessibility option somewhere to speak them.
Failing that, there is pybraces, which was written as a practical joke but might actually be useful to you with a bit of work.

If you're on Windows, I strongly recommend you take a look at EdSharp from:
http://empowermentzone.com/EdSharp.htm
It supports all of the leading Windows screenreaders, it can be configured to speak the indentation levels of code, or it has a built in utility called PyBrace that can convert to and from braces syntax if you want to do that instead, and it supports all kinds of other features programmers have come to expect in our text editors. I've been using it for years, for everything from PHP to JavaScript to HTML to Python, and I love it.

All of these "no you can't" types of answers are really annoying. Of course you can.
It's a hack, but you can do it.
http://timhatch.com/projects/pybraces/
uses a custom encoding to convert braces to indented blocks before handing it off to the interpreter.
As an aside, and as someone new to python - I don't accept the reasoning behind not even allowing braces/generic block delimiters ... apart from that being the preference of the python devs. Braces at least won't get eaten accidentally if you're doing some automatic processing of your code or working in an editor that doesn't understand that white space is important. If you're generating code automatically, it's handy to not have to keep track of indent levels. If you want to use python to do a perl-esque one-liner, you're automatically crippled. If nothing else, just as a safeguard. What if your 1000 line python program gets all of its tabs eaten? You're going to go line-by-line and figure out where the indenting should be?
Asking about it will invariably get a tongue-in-cheek response like "just do 'from __ future __ import braces'", "configure your IDE correctly", "it's better anyway so get used to it" ...
I see their point, but hey, if i wanted to, i could put a semicolon after every single line. So I don't understand why everyone is so adamant about the braces thing. If you need your language to force you to indent properly, you're not doing it right in the first place.
Just my 2c - I'm going to use braces anyway.

I appreciate your problem, but think you are specifying the implementation instead of the problem you need solved. Instead of converting to braces, how about working on a way for your screen reader to tell you the indentation level?
For example, some people have worked on vim syntax coloring to represent python indentation levels. Perhaps a modified syntax coloring could produce something your screen reader would read?

Searching an accessible Python IDE, found this and decided to answer.
Under Windows with JAWS:
Go to Settings Center by pressing JawsKey+6 (on the number row above the letters) in your favorite text editor. If JAWS prompts to create a new configuration file, agree.
In the search field, type "indent"
There will be only one result: "Say indent characters". Turn this on.
Enjoy!
The only thing that is frustrating for us is that we can't enjoy code examples on websites (since indent speaking in browsers is not too comfortable — it generates superfluous speech).
Happy coding from another Python beginner).

I use eclipse with the pydev extensions since it's an IDE I have a lot of experience with. I also appreciate the smart indentation it offers for coding if statements, loops, etc. I have configured the pindent.py script as an external tool that I can run on the currently focused python module which makes my life easier so I can see what is closed where with out having to constantly check indentation.

There are various answers explaining how to do this. But I would recommend not taking this route. While you could use a script to do the conversion, it would make it hard to work on a team project.
My recommendation would be to configure your screen reader to announce the tabs. This isn't as annoying as it sounds, since it would only say "indent 5" rather than "tab tab tab tab tab". Furthermore, the indentation would only be read whenever it changed, so you could go through an entire block of code without hearing the indentation level. In this way hearing the indentation is no more verbose than hearing the braces.
As I don't know which operating system or screen reader you use I unfortunately can't give the exact steps for achieving this.

Edsger Dijkstra used if ~ fi and do ~ od in his "Guarded Command Language", these appear to originate from the Algol68. There were also some example python guarded blocks used in RosettaCode.org.
fi = od = yrt = end = lambda object: None;
class MyClass(object):
def myfunction(self, arg1, arg2):
for i in range(arg1) :# do
if i > 5 :# then
print i
fi
od # or end(i) #
end(myfunction)
end(MyClass)
Whitespace mangled python code can be unambiguously unmangled and reindented if one uses
guarded blocks if/fi, do/od & try/yrt together with semicolons ";" to separate statements. Excellent for unambiguous magazine listings or cut/pasting from web pages.
It should be easy enough to write a short python program to insert/remove the guard blocks and semicolons.