Table of Contents

Python layer

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python.png

1 Description

This layer adds support for the Python language.

1.1 Features:

2 Install

2.1 Layer

To use this configuration layer, add it to your ~/.spacemacs. You will need to add python to the existing dotspacemacs-configuration-layers list in this file.

2.2 Choosing a backend

To choose a default backend set the layer variable python-backend:

(python :variables python-backend 'anaconda)

Alternatively the lsp backend will be automatically chosen if the layer lsp is used and you did not specify any value for python-backend.

Backend can be chosen on a per project basis using directory local variables (files named .dir-locals.el at the root of a project), an example to use the lsp backend:

;;; Directory Local Variables
;;; For more information see (info "(emacs) Directory Variables")

((python-mode (python-backend . lsp)))

Note: you can easily add a directory local variable with SPC f v d.

The available options are:

symbol description
'anaconda Default
'lsp python-language-server package

3 Backends

3.1 Anaconda

anaconda-mode tries to install the dependencies itself but sometimes it does not work and you may encounter the following message when opening a python buffer:

Blocking call to accept-process-output with quit inhibited!!

To fix this, install the anaconda-mode anaconda-deps by hand:

pip install --upgrade "jedi>=0.13.0" "json-rpc>=1.8.1" "service_factory>=0.1.5"

If you encounter problems with Jedi 1.0 consider downgrading to 0.13.0. See this issue for details.

Source: https://github.com/proofit404/anaconda-mode#issues

If you are facing errors such as "Unable to run anaconda-mode server", try setting your PYTHONPATH as explained at https://github.com/proofit404/anaconda-mode#pythonpath

3.2 Language Server Protocol

The lsp backend can use either of the following language server implementations:

symbol description
'pyls python-language-server package (default)
'mspyls Microsoft python language server

pyls is used by default - to use the Microsoft server, set the python-lsp-server layer variable as follows:

(python :variables python-backend 'lsp python-lsp-server 'mspyls)

3.2.1 python-language-server

You just have to install python language server package:

pip install python-language-server

Additionally you can install the following other packages:

# for import sorting
pip install pyls-isort
# for mypy checking (python 3.4+ is needed)
pip install pyls-mypy

If you've installed the language server and related packages as development dependencies in a pipenv environment, you'll want to set the python-pipenv-activate config variable to t. This activates your pipenv before enabling the lsp backend.

3.2.2 Microsoft python language server

Paraphrasing the instructions provided by the author of the lsp-python-ms package:

git clone https://github.com/Microsoft/python-language-server.git
cd python-language-server/src/LanguageServer/Impl
dotnet build -c Release
dotnet publish -c Release -r <RUNTIME>

where <RUNTIME> is one of the runtime IDs supported by dotnet core. One of linux-x64, osx-x64, win10-x64 should cover most use cases.

The default package configuration assumes the executable is located in a folder included in your system path. To use the latest built version in a cloned git repo, use the python-lsp-git-root config variable, e.g.:

(setq-default dotspacemacs-configuration-layers
  '((python :variables
            python-backend 'lsp
            python-lsp-server 'mspyls
            python-lsp-git-root "~/dev/python/python-language-server")))

N.B. If you're using Arch linux or a derivative distribution, you can install the microsoft-python-language-server package from the AUR.

4 Additional tools

4.1 Syntax checking

Syntax checking uses flake8 package:

pip install flake8

4.2 Test runner

Both nose and pytest are supported. By default nose is used. To choose your test runner set the layer variable python-test-runner to either nose or pytest.

(setq-default dotspacemacs-configuration-layers
  '((python :variables python-test-runner 'pytest)))

If you need both then you can set python-test-runner to a list like this:

(setq-default dotspacemacs-configuration-layers
  '((python :variables python-test-runner '(pytest nose))))

This means that pytest is your primary test runner. To use the secondary test runner you can call the test functions with a prefix argument e.g. SPC u SPC m t t to run one test with nose.

To set project specific test runners you can set python-test-runner in a directory local variable in your project root. SPC f v d in Spacemacs. See the official documentation for more information.

The root of the project is detected with a .git directory or a setup.cfg file.

4.3 Buffer formatting

One of YAPF (the default), black or lsp may be selected as the formatter, via python-formatter, as 'yapf, 'black or lsp respectively.

(setq-default dotspacemacs-configuration-layers '(
  (python :variables python-formatter 'yapf)))

The key binding SPC m = invokes the selected formatter on the current buffer when in non LSP python mode otherwise SPC m == is used.

Note that a specific formatter may also be invoked unconditionally via yapfify-buffer, blacken-buffer or lsp-format-buffer, provided these are installed.

4.4 Automatic buffer formatting on save

To enable automatic buffer formatting on save set the variable python-format-on-save to t. The formatter specified by python-formatter will be used.

(setq-default dotspacemacs-configuration-layers '(
  (python :variables python-format-on-save t)))

4.5 Automatic save of buffer when testing

By default a buffer is automatically saved before tests are executed upon it, you can disable this feature by setting python-save-before-test to nil.

(setq-default dotspacemacs-configuration-layers '(
  (python :variables python-save-before-test nil)))

4.6 autoflake

To be able to suppress unused imports easily, install autoflake:

pip install autoflake

4.7 pylookup

To use pylookup on SPC m h H, make sure you update the database first, using SPC SPC pylookup-update.

4.8 dap-mode debugger (only for lsp backend)

To use dap-mode for debugging do:

pip install "ptvsd>=4.2"

5 Configuration

5.1 Fill column

If you want to customize the fill column value, use something like this inside the user-init function in your .spacemacs:

(setq-default dotspacemacs-configuration-layers '(
    (python :variables python-fill-column 99)))

5.2 Sort imports

If you want imports to be automatically sorted when you save a file (using isort), set the python-sort-imports-on-save variable in the python layer config section:

(setq-default dotspacemacs-configuration-layers
  '((python :variables python-sort-imports-on-save t)))

or as a directory-local variable (for per-project settings).

5.3 Importmagic

Install importmagic and epc for importmagic functionality.

pip install importmagic epc

6 Management of Python versions and virtual environments

6.1 Manage virtual environments with pyvenv

A virtual environment provides isolation of your Python package versions. For a general overview see this site. Virtualenvwrapper which is also explained in the previous link, is a program which manages your virtual environments in a central location set by the WORKON_HOME environment variable.

Spacemacs integration of virtual environments and virtualenvwrapper is provided by the pyvenv package. It provides the following key bindings:

Key binding Description
SPC m V a activate a virtual environment in any directory
SPC m V d deactivate active virtual environment
SPC m V w work on virtual environment in WORKON_HOME

6.2 Manage multiple Python versions with pyenv

If you need multiple Python versions (e.g. Python 2 and Python 3) then take a look at pyenv. It enables the installation and management of multiple Python versions. This blogpost gives a good overview on how to use the tool. Spacemacs integration is provided by pyenv mode which has the following key bindings.

Key binding Description
SPC m v s set a pyenv environment with pyenv
SPC m v u unset a pyenv environment with pyenv

Pyenv can also manage virtual environments for each of the Python versions it has installed. Those will be listed alongside your Python versions.

6.2.1 Automatic activation of local pyenv version

A project-specific pyenv version may be written to a file called .python-version using the pyenv local command.

Spacemacs can search in parent directories for this file, and automatically set the pyenv version. The behavior can be set with the variable python-auto-set-local-pyenv-version to:

  • on-visit (default) set the version when you visit a python buffer,
  • on-project-switch set the version when you switch projects,
  • nil to disable.

The same is also possible on pyvenv with a file called .venv that specifies either an absolute or relative path to a virtualenv directory. A relative path is checked relative to the location of .venv, then relative to pyvenv-workon-home. .venv can also be a virtualenv directory. The behavior can be set with the variable python-auto-set-local-pyvenv-virtualenv to:

  • on-visit (default) set the virtualenv when you visit a python buffer,
  • on-project-switch set the virtualenv when you switch projects,
  • nil to disable.

7 Key bindings

7.1 Inferior REPL process

Start a Python or iPython inferior REPL process with SPC m s i. If ipython is available in system executable search paths, ipython will be used to launch python shell; otherwise, default python interpreter will be used. You may change your system executable search path by activating a virtual environment.

Send code to inferior process commands:

Key binding Description
SPC m s b send buffer and keep code buffer focused
SPC m s B send buffer and switch to REPL in insert mode
SPC m s f send function and keep code buffer focused
SPC m s F send function and switch to REPL in insert mode
SPC m s i start inferior REPL process
SPC m s r send region and keep code buffer focused
SPC m s R send region and switch to REPL in insert mode
CTRL+j next item in REPL history
CTRL+k previous item in REPL history

7.2 Running Python Script in shell

To run a Python script like you would in the shell press SPC m c c to start the Python script in comint mode. This is useful when working with multiple Python files since the REPL does not reload changes made in other modules.

Key binding Description
SPC m c c Execute current file in a comint shell
SPC m c C Execute current file in a comint shell and switch to it in insert state

Note: With the universal argument SPC u you can enter a new compilation command.

7.3 Testing

Test commands start with m t. To use the secondary test runner call the function with a prefix argument, for example SPC u SPC m t a.

No Debug Description
SPC m t a launch all tests of the project
SPC m t b launch all tests of the current buffer (same as module)
SPC m t l launch last tests
SPC m t m launch all tests of the current module
SPC m t s launch all tests of the current suite (only with nose)
SPC m t t launch the current test (function)
Debug Description
SPC m t A launch all tests of the project in debug mode
SPC m t B launch all tests of the current buffer (module) in debug mode
SPC m t M launch all tests of the current module in debug mode
SPC m t S launch all tests of the current suite in debug mode (only with nose)
SPC m t T launch the current test (function) in debug mode

7.4 Refactoring

Key binding Description
SPC m r f fix a missing import statement with importmagic
SPC m r i remove unused imports with autoflake
SPC m r I sort imports with isort

7.5 Pip package management

In python buffer type SPC m P to open buffer listing all installed pip packages in the currently activated virtual environment.

Note: To open this menu from outside a python buffer type SPC SPC pippel-list-packages RET.

In the package list buffer:

Key binding Description
RET follow link (pippel-menu-visit-homepage)
d mark for deletion (pippel-menu-mark-delete)
i prompt user for packages (pippel-install-package)
m remove mark (pippel-menu-mark-unmark)
r refresh package list (pippel-list-packages)
U mark all upgradable (pippel-menu-mark-all-upgrades)
u mark for upgrade (pippel-menu-mark-upgrade)
x perform marked package menu actions (pippel-menu-execute)

7.6 Live coding

Live coding is provided by the live-py-plugin.

Key binding Description
SPC m l Toggle live-py-mode

7.7 Other Python commands

Key binding Description
SPC m = or SPC m = = reformat the buffer using default formatter specified in python-formatter
SPC m d b toggle a breakpoint using wdb, ipdb, pudb, pdb or python3.7 (and above)
SPC m g a go to assignment using anaconda-mode-find-assignments (C-o to jump back)
SPC m g b jump back
SPC m g g go to definition using anaconda-mode-find-definitions (C-o to jump back)
SPC m g u navigate between usages with anaconda-mode-find-references
SPC m h d look for documentation using helm-pydoc
SPC m h h quick documentation using anaconda
SPC m h H open documentation in firefox using pylookup
SPC m v a activate a virtual environment in any directory
SPC m v d deactivate active virtual environment
SPC m v s set a pyenv environment with pyenv
SPC m v u unset a pyenv environment with pyenv
SPC m v w work on virtual environment in WORKON_HOME
SPC m v p a activate pipenv in current project
SPC m v p d deactivate pipenv in current project
SPC m v p i install module into pipenv environment
SPC m v p o open pipenv module in buffer
SPC m v p s launch pipenv shell in current project
SPC m v p u uninstall module from pipenv environment

7.8 Debugger

Using the dap layer you'll get access to all the DAP key bindings, see the complete list of key bindings on the dap layer description.

Author: root

Created: 2019-11-10 Sun 14:17

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