spacemacs/layers/+lang/python/README.org

Python layer

• Description
  • Features
• Install
  • Layer
  • Test runner
  • Anaconda dependencies
  • Automatic buffer formatting on save
  • autoflake
  • pylookup
• Management of Python versions and virtual environments
  • Manage virtual environments with pyvenv
  • Manage multiple Python versions with pyenv
    • Automatic activation of local pyenv version
• Key Bindings
  • Inferior REPL process
  • Running Python Script in shell
  • Testing
  • Refactoring
  • Other Python commands
• Configuration
  • Fill column

Description

This layer adds support for the Python language.

Features

• Auto-completion using anaconda-mode
• Code Navigation using anaconda-mode
• Documentation Lookup using anaconda-mode and pylookup
• Test Runners using nose.el or pytest
• Virtual Environment using pyvenv and pyenv
• semantic mode is enabled
• PEP8 compliant formatting via YAPF
• Suppression of unused import with autoflake
• Use the % key to jump between blocks with evil-matchit

Install

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.

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.

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

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

Anaconda dependencies

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  jedi==0.8.1 json-rpc==1.8.1 service_factory==0.1.2

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

Automatic buffer formatting on save

To enable automatic buffer formatting on save with YAPF set the variable python-enable-yapf-format-on-save to t.

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

autoflake

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

  pip install autoflake

pylookup

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

Management of Python versions and virtual environments

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 keybindings:

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

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 managment 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 keybindings.

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.

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. If this file is not found then the global pyenv version is set.

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.

Key Bindings

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

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.

Testing

Test commands start with m t:

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 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

Refactoring

Key Binding	Description
SPC m r i	remove unused imports with autoflake

Other Python commands

Key Binding	Description
SPC m =	Reformat the buffer according to PEP8 using YAPF
SPC m d b	toggle a breakpoint
SPC m g g	go to definition using anaconda-mode-find-definitions (C-o to jump back)
SPC m g a	go to assignment using anaconda-mode-find-assignments (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 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 a	activate a virtual environment in any directory
SPC m V d	deactivate active virtual environment

Configuration

Fill column

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

(setq python-fill-column 99)