Develop Reference

How do I make autopep8 allow a comment at the end of a line?

I'm trying to format my code with autopep8 (because this appears to be the default one in VSCode). But there is a problem with it:
I am using a lib that doesn't care about typing, so I need to suffix some lines with # type:ignore to make the linter ignore that particular file. But when formatting (with autopep8) the formatter moves the comment to the line above. Then my linter doesn't ignore the line like it should.
So with e.g. this code:
somevar = dumblib.foobar() #type:ignore
I hit Shift+Alt+F to format, and then the code is formatted to this:
# type:ignore
somevar = dumblib.foobar()
And then, the linter complains that the type of "somevar" is unknonwn.
How can I prevent autopep8 from moving the comment during a reformat?

It's a relatively old question but in case others also struggle with this, I will leave a solution that helped me.
The autopep8 rule that is responsible for moving comments above the code line is nothing but a max-line-length. I was able to fix this by increasing the maximum line length. To do this I created a configuration file in my project (.pep8) and configured vscode to use it (in the autopep8 extension settings).
Configuration file contents:
[pep8]
max-line-length = 160

How can I change tab size of python code in vs code

When I type the python code in vs code, indent tab size is 2. But when I save the file, tab size is changed to 4. I think this is because of autopep8.
How can I change the tab size, when I save the python code?
※ I already change editor.tabsize to 2

It's recommended to set '--indent-size' to change the autopep8 behavior. You can refer to this page for details. But I can't make it works in this way, so I directly
make a change in autopep8.py(under site-packages which you installed the autopep8) file, at the line of 112 change "DEFAULT_INDENT_SIZE = 4" to "DEFAULT_INDENT_SIZE = 2". It works and it's the same to set '--indent-size' in logic.

You will need to configure autopep8 to keep indent to two spaces. That way it won't undo how VS Code is inserting spaces for you.

introduce <Tab> in new line while creating a block for python files in vim

I want to introduce a tab character in the new line for creating a new block in vim for python files.
Example
when I write
if(a < 5):
and press Enter, the cursor should come in next line with a tab after if in vertical alignment from the above line. Something like this
if(a < 5):
a = 5
I have configured my .vimrc file like this
set nu
set autoindent
set tabstop=4
syntax enable
set showmatch
colorscheme gruvbox
set bg=dark
"automatically creates a block after :
autocmd FileType python inoremap :<CR> :<CR><Tab>
Note:
1) Last line, I have written for the intended purpose mentioned in my question.
2) autoindent is set.
3) I dont want to use any plugin.
Problem I am facing:
When I press Enter after : , in addition to tab, one extra space is also created which creates wrong indentation.
Thanks in advance for helping

The way you're trying to do this is the hard way. There's a filetype plugin and a Python syntax type and it already knows what to do.
filetype plugin indent on
And don't use set autoindent. It's not very intelligent, it just copies the indent from the previous line. It's the opposite of what you're trying to do.
Files ending in .py should automatically get the right settings. If you need to force the current syntax type in a buffer, you can do that with
:set filetype=python
If you want to use tabs instead of spaces,
" Globally
set noexpandtab
" Python only
autocmd FileType python set noexpandtab
However, I'll note that using tabs in Python is not recommended and goes against published best practices (see PEP 8).
Lastly I'll mention that "plugin" is just a Vim term. All of this ships with Vim by default, this does not create a third-party dependency.

macVim: line continuation in python creates unnecessary tab?

Whenever I want to use line continuation in my python script using macVim, I receive the following format:
a = one,\
two,\
three
instead of:
a = one,\
two,\
three
I've rifled through help, and was unable to locate what exactly is causing macVim to append an extra tab upon using line continuation.
Note: I currently have the following in my .vimrc file:
set tabstop=4
set shiftwidth=4
set expandtab
set softtabstop=4

You have your tabs set to 4 and not 2
Make sure that you have
filetype plugin indent on
You can also use something as followed in your .vimrc as a oneliner for defaults instead of adding them on separate lines
Use 2 instead of 4
set ts=2 sts=2 sw=2 noexpandtab

Your settings are almost fine. In Python code, the tab settings should always be
:set tabstop=8 shiftwidth=4 softtabstop=4 expandtab
These settings honour the recommendations in the "Style guide for Python code" known as PEP 8 and are universally followed in Python code. Stick to these settings, or even better, set up an autocommand that sets them automatically. In your vimrc:
autocmd FileType python setlocal ts=8 sw=4 sts=4 et
Now on to your problem: This is caused by the default indentation rules in Vim's indent script for Python. Fortunately, these rules can be customised. In your case you just need to put the following line in your vimrc.
let g:pyindent_continue = '&shiftwidth'
(In newer versions of Vim, use 'shiftwidth()' instead of '&shiftwidth'.)
For more information, look up :h ft-python-indent.

Errors editing python with Vim

When I edit a python file in Vim (using MacVim), and I press o to insert a new line, Vim throws the following errors:
Error detected while processing function <SNR>20_CheckAlign..GetPythonIndent:
line 30:
E121: Undefined variable: dummy
Press ENTER or type command to continue
Error detected while processing function <SNR>20_CheckAlign..GetPythonIndent:
line 30:
E15: Invalid expression: line('.') < 7 ? dummy : synIDattr(synID(line('.'), col('.')
, 1), 'name') =~ '\(Comment\|String\)$'
How do I fix this?

I figured out the problem. It was throwing an error whenever the file's tab settings were different from the editor's tab settings. For example, my test.py file was set to 2 spaces per tab, with tabs expanded into spaces, whereas my editor was set to 4 spaces per tab, no expand.
So the solution workaround was to set Vim's tab settings to the settings of the python file being edited.

Use the following modeline in your python files, that its tab settings are consistent.
# vim: tabstop=4 expandtab shiftwidth=4 softtabstop=4
Alternately, you have them set in your .vimrc file too.
set tabstop=4
set shiftwidth=4
set softtabstop=4
set expandtab
These are minimal set of things which you ensure consistency when working with python file.
There are some great vimrc examples available which you can use as well.

Changing the indentation settings did not work for me so I worked around this by modifying the python indentation file (/path/to/vim/indent/python.vim).
In the GetPythonIndent function I simply replaced all instances of dummy with 0. This fixed the problem for me.
Alternatively you could just set s:maxoff to something ridiculously high but this is somewhat less elegant.

To resolve the problem it seems one must edit the function GetPythonIndent() in /path/to/vim/indent/python.vim.
To do this, one must read in the help docs, user_30, indent, indentexpr, and indent-expression (also, C-indenting contains general info that will help explain what's going on).
The simplest solution therefore is to switch indenting off when you are editing a python file, until such time as you have time to deal with this irritating bug:
:set indentexpr=""
You will see in /path/to/vim/indent/python.vim that expression is set to run the buggy function GetPythonIndent:
setlocal indentexpr=GetPythonIndent(v:lnum)
Set it to "" there to save the inconvenience of unsetting it every time you open a python file.
Dani's answer above looks like it might be the better solution, since it would preserve some form of auto-indentation. But this will give you instant relief and save having to read and understand the buggy func.