Provided by: elpa-elpy_1.32.0-2_all 
NAME
elpy - Elpy Documentation
Elpy is the Emacs Python Development Environment. It aims to provide an easy to install,
fully-featured environment for Python development.
INTRODUCTION
Overview
Elpy is an extension for the Emacs text editor to work with Python projects. This
documentation explains how to use Elpy to work on Python project using Emacs, but it does
not aim to be an introduction to either Emacs or Python.
You can read a quick tour of Emacs, or read the built-in tutorial by running C-h t in the
editor. That is, you hold down the control key and hit h (the canonical help key in
Emacs), release both, and hit t (for tutorial).
For Python, you can read the basic tutorial. If you already know Python, you should check
out some best practices.
Once you have these basics, you can go on to install Elpy.
Installation
With use-package
Simply add the following lines to you .emacs (or .emacs.d/init.el, or equivalent):
(use-package elpy
:ensure t
:init
(elpy-enable))
Or if you want to defer Elpy loading:
(use-package elpy
:ensure t
:defer t
:init
(advice-add 'python-mode :before 'elpy-enable))
From apt (Debian ≥10 an Ubuntu ≥18.10)
Users of Debian ≥10 or Ubuntu ≥18.10 can skip the instructions above this line and may
simply install Elpy and all of its recommended dependencies with the following command::
sudo apt install elpa-elpy
Elpy can then be activated by running M-x elpy-enable. This can be made automatic by
adding the following to your .emacs:
(elpy-enable)
In order to use all the features (such as navigation with M-.), you'll need to install
some python libraries. You can do that easily by typing M-x elpy-config RET, and
following the instructions.
Manually from Melpa
The main Elpy package is installed via the Emacs package interface, package.el. First, you
have to add Elpy's package archive to your list of archives, though. Add the following
code to your .emacs file and restart Emacs:
(require 'package)
(add-to-list 'package-archives
'("melpa-stable" . "https://stable.melpa.org/packages/"))
Now you can run M-x package-refresh-contents to download a fresh copy of the archive
contents, and M-x package-install RET elpy RET to install elpy. If you want to enable Elpy
by default, you can simply add the following to your .emacs:
(package-initialize)
(elpy-enable)
Congratulations, Elpy is now successfully installed!
Manually from sources
If you want to test a specific branch or a PR that has not been merged yet, you will have
to install Elpy from sources.
• First, clone the repository containing the branch you are interested in:
git clone https://github.com/USER/elpy.git
cd elpy
Then check out the branch associated to the PR you want to try:
git checkout BRANCH_NAME
• Now switch to Emacs and add Elpy's sources to the load path:
(add-to-list 'load-path "/path/to/elpy")
• Finally, load Elpy files:
(load "elpy")
(load "elpy-rpc")
(load "elpy-shell")
(load "elpy-profile")
(load "elpy-refactor")
(load "elpy-django")
Configuration
You can easily configure Elpy to your own preferences. All options are available through a
unified interface, accessible with the following command:
M-x elpy-config
Show the current Elpy configuration, point out possible problems, and provide a
quick interface to relevant customization options.
Packages needed by Elpy can be installed and updated from this interface.
QUICKSTART
Once installed, Elpy will automatically provide code completion, syntax error highlighting
and function signature (in the modeline) for python files.
Useful keybindings
Elpy has quite a lot of keybindings, but the following ones should be enough to get you
started:
C-c C-c (elpy-shell-send-region-or-buffer)
Evaluate the current script (or region if something is selected) in an interactive
python shell. The python shell is automatically displayed aside of your script.
C-RET (elpy-shell-send-statement-and-step)
Evaluate the current statement (current line plus the following nested lines).
Useful for evaluating a function or class definition or a for loop.
C-c C-z (elpy-shell-switch-to-shell)
Switch between your script and the interactive shell.
C-c C-d (elpy-doc)
Display documentation for the thing under cursor (function or module). The
documentation will pop in a different buffer, that can be closed with q.
Go further
Elpy offers a lot of features, including code navigation, debugging, testing, profiling
and support for virtual environments. Feel free to explore the documentation, everything
is there !
EDITING
Emacs Basics
Elpy is an extension to Emacs, and as such the standard bindings in Emacs are available.
This manual is not meant to be an introduction to Emacs, but this section will still
highlight some features in Emacs that are especially useful for Python editing.
Movement keys in Emacs often use fbnp for forward, backward, next (down) and previous
(up). k and backspace (DEL) are for deleting. These are combined with the Control, Meta
and Control-Meta modifiers. Control generally refers to the simplest form. C-f moves one
character forward. Meta changes this to affect words, that is, consecutive sequences of
alphanumeric characters. The Control-Meta combination then affects whole expressions.
In the following table, | refers to the position of point.
┌─────────────┬───────┬──────────────┐
│Before │ Key │ After │
├─────────────┼───────┼──────────────┤
│|hello_world │ C-f │ h|ello_world │
├─────────────┼───────┼──────────────┤
│|hello_world │ M-f │ hello|_world │
├─────────────┼───────┼──────────────┤
│|hello_world │ C-M-f │ hello_world| │
└─────────────┴───────┴──────────────┘
Expression-based commands will also work on strings, tuples, dictionaries, or any balanced
groups of parentheses. This works for all movement keys (f, b, n, p), with next and
previous moving to the next or previous group of parens. It also works with forward and
backward deletion (d and DEL/<backspace>, respectively) for character and word groups, but
not for expressions. To delete the expression after point, use C-M-k. For the expression
before point, you can use C-M-b C-M-k.
If you enable subword-mode, Emacs will also consider CamelCase to be two words instead of
one for the purpose of these operations.
In addition to the above, Emacs also supports moving up or down inside nested parentheses
groups. C-M-d will move down into the next enclosed group of parentheses, while C-M-u will
move up to the directly enclosing group of parentheses.
Finally, a lot of Elpy's commands change their behavior when the prefix argument is given.
That is, hit C-u before the command. In Elpy, the prefix argument often disables any
attempt by the command at being smart, in case it would get it wrong.
Moving By Indentation
C-down (elpy-nav-forward-block)
C-up (elpy-nav-backward-block)
These commands are used to navigate between lines with same indentation as the
current line. Point should be placed on the first non-whitespace character of the
line and then use C-down to move forward or C-up to move backward.
C-left (elpy-nav-backward-indent)
C-right (elpy-nav-forward-indent)
These commands are used to navigate between indentation levels. C-left moves point
to previous indent level or over previous word. C-right moves point to next indent
level or over the next word.
Moving the Current Region
M-down (elpy-nav-move-line-or-region-down)
M-up (elpy-nav-move-line-or-region-up)
M-left (elpy-nav-indent-shift-left)
M-right (elpy-nav-indent-shift-right)
Elpy can move the selected region (or the current line if no region is selected) by
using the cursor keys with meta. Left and right will dedent or indent the code,
while up and down will move it line-wise up or down, respectively.
IDE FEATURES
Projects
Elpy supports the notion of projects, a related collection of files under a common
directory. This common directory is called the project root. A number of Elpy's commands
work on all files inside the project root.
C-c C-f (elpy-find-file)
Find a file in the current project. This uses a search-as-you-type interface for
all files under the project root.
A prefix argument enables "do what I mean" mode. On an import statement, it will
try to open the module imported. Elsewhere in a file, it will look for an
associated test or implementation file, and if found, open that. If this fails,
either way, it will fall back to the normal find file in project behavior.
If the current file is called foo.py, then this will search for a test_foo.py in
the same directory, or in a test or tests subdirectory. If the current file is
already called test_foo.py, it will try and find a foo.py nearby.
This command uses projectile or find-file-in-project under the hood, so you need
one of them to be installed.
C-c C-s (elpy-rgrep-symbol)
Search the files in the current project for a string. By default, this uses the
symbol at point. With a prefix argument, it will prompt for a regular expression to
search.
This is basically a grep -r through the project.
In addition to these two commands, elpy-check also supports optionally checking all files
in the current project.
Elpy's idea of the project root and which files belong to a project and which don't can be
influenced as well.
M-x elpy-set-project-root
Set the current project root directory. This directory should contain all files
related to the current project.
elpy-project-ignored-directories (Customize Option)
When Elpy searches for files in the current project, it will ignore files in
directories listed here.
elpy-project-root-finder-functions (Customize Option)
To find the project root, Elpy can utilize a number of heuristics. With this
option, you can configure which are used.
To configure Elpy specifically for a single project, you can use Emacs' Directory
Variables. Elpy provides a simple interface to this.
M-x elpy-set-project-variable
Set or change the value of a project-wide variable. With a prefix argument, the
value for the variable is removed.
This only takes effect in new buffers.
Completion
When you type Python code, Elpy will try and figure out possible completions and provide
them in a suggestion window. If Elpy doesn't do so automatically, you can force it to
complete right where you are.
M-TAB (elpy-company-backend)
Provide completion suggestions for a completion at point.
You can use cursor keys or M-n and M-p to scroll through the options, RET to use the
selected completion, or TAB to complete the common part.
On any completion option, C-d or <f1> will display a temporary window with documentation.
C-w will display a temporary window showing the source code of the completion to get some
context.
Elpy uses Company Mode for the completion interface, so its documentation is a good place
for further information.
elpy-get-info-from-shell (Customize Option)
If t, use the shell to gather docstrings and completions. Normally elpy provides
completion and documentation using static code analysis (from jedi). With this
option, elpy will add the completion candidates and the docstrings from the
associated python shell; This activates fallback completion candidates for cases
when the static code analysis fails.
Navigation
Elpy supports advanced navigation features.
M-. (elpy-goto-definition)
Go to the location where the identifier at point is defined. This is not always
easy to make out, so the result can be wrong. Also, the backends can not always
identify what kind of symbol is at point. Especially after a few indirections, they
have basically no hope of guessing right, so they don't.
C-x 4 M-. (elpy-goto-definition-other-window)
Same as elpy-go-to-definition (with the same caveats) but goes to the definition of
the symbol at point in other window, if defined.
M-* (pop-tag-mark)
Go back to the last place where M-. was used, effectively turning M-. and M-* into
a forward and backward motion for definition lookups.
C-c C-o (elpy-occur-definitions)
Search the buffer for a list of definitions of classes and functions.
If you use an Emacs version superior to 25, Elpy will define the necessary backends for
the xref package.
M-. (xref-find-definitions)
Find the definition of the identifier at point.
C-x 4 . (xref-find-definition-other-window)
Like M-. but switch to the other window.
C-x 5 . (xref-find-definition-other-frame)
Like M-. but switch to the other frame.
M-, (xref-pop-marker-stack)
Go back to the last place where M-. was used, effectively turning M-. and M-, into
a forward and backward motion for definition lookups.
M-? (xref-find-references)
Find references for an identifier of the current buffer.
C-M-. (xref-find-apropos)
Find all meaningful symbols that match a given pattern.
Interactive Python
Emacs can run a Python interpreter in a special buffer, making it much easier to send code
snippets over. Elpy provides additional functionality to seamlessly work with interactive
Python in a style similar to ESS.
Interpreter Setup
Elpy uses the Python interpreter setup from the Emacs python package. This section briefly
summarizes some common setups; add the one you need to your .emacs file. Note that the
code below (and Elpy in general) require at least Emacs 24.4.
Use the Python standard interpreter (default):
(setq python-shell-interpreter "python"
python-shell-interpreter-args "-i")
Use Jupyter console (recommended for interactive Python):
(setq python-shell-interpreter "jupyter"
python-shell-interpreter-args "console --simple-prompt"
python-shell-prompt-detect-failure-warning nil)
(add-to-list 'python-shell-completion-native-disabled-interpreters
"jupyter")
Use IPython:
(setq python-shell-interpreter "ipython"
python-shell-interpreter-args "-i --simple-prompt")
Note that various issues with plotting have been reported when running IPython 5 in Emacs
under Windows. We recommend using Jupyter console instead.
If you have an older version of IPython and the above code does not work for you, you may
also try:
(setenv "IPY_TEST_SIMPLE_PROMPT" "1")
(setq python-shell-interpreter "ipython"
python-shell-interpreter-args "-i")
As an IPython_ user, you might be interested in the `Emacs IPython
Notebook`_ or an `Elpy layer`_ for Spacemacs_, too.
The Shell Buffer
C-c C-z (elpy-shell-switch-to-shell)
Switch to buffer with a Python interpreter running, starting one if necessary.
By default, Elpy tries to find the root directory of the current project (git, svn
or hg repository, python package or projectile project) and starts the python
interpreter here. This behaviour can be suppressed with the option
elpy-shell-starting-directory.
elpy-shell-starting-directory (Customize Option)
Govern the directory in which Python shells will be started. Can be 'project-root
(default) to use the current project root, 'current-directory to use the buffer
current directory, or a string indicating a specific path.
M-x elpy-shell-toggle-dedicated-shell
By default, python buffers are all attached to a same python shell (that lies in
the *Python* buffer), meaning that all buffers and code fragments will be send to
this shell. elpy-shell-toggle-dedicated-shell attaches a dedicated python shell
(not shared with the other python buffers) to the current python buffer. To make
this the default behavior (like the deprecated option elpy-dedicated-shells did),
use the following snippet:
(add-hook 'elpy-mode-hook (lambda () (elpy-shell-toggle-dedicated-shell 1)))
M-x elpy-shell-set-local-shell
Attach the current python buffer to a specific python shell (whose name is asked
with completion). You can use this function to have one python shell per project,
with:
(add-hook 'elpy-mode-hook (lambda () (elpy-shell-set-local-shell (elpy-project-root))))
C-c C-k (elpy-shell-kill)
Kill the associated python shell.
C-c C-K (elpy-shell-kill-all)
Kill all active python shells.
Evaluating code fragments
Elpy provides commands to send the current Python statement (e), function definition (f),
class definition (c), top-level statement (s), group of Python statements (g), cell (w),
region (r), or buffer (b) to the Python shell for evaluation. These commands are bound to
prefix C-c C-y, followed by the single character indicating what to send; e.g., C-c C-y e
sends the Python statement at point.
Each of the commands to send code fragments to the shell has four variants, one for each
combination of: whether or not the point should move after sending ("step"), and whether
or not the Python shell should be focused after sending ("go"). Step is activated by C-,
go by S-. For example:
C-c C-y e (elpy-shell-send-statement)
Send the current statement to the Python shell and keep point position. Here
statement refers to the Python statement the point is on, including potentially
nested statements. If point is on an if/elif/else clause send the entire if
statement (with all its elif/else clauses). If point is on a decorated function,
send the decorator as well.
C-c C-y C-e (elpy-shell-send-statement-and-step)
Send the current statement to the Python shell and move point to first subsequent
statement.
Also bound to C-RET.
C-c C-y E (elpy-shell-send-statement-and-go)
Send the current statement to the Python shell, keeping point position, and switch
focus to the Python shell buffer.
C-c C-y C-S-E (elpy-shell-send-statement-and-step-and-go)
Send the current statement to the Python shell, move point to first subsequent
statement, and switch focus to the Python shell buffer.
Elpy provides support for sending multiple statements to the shell.
C-c C-y O (elpy-shell-send-group-and-step)
Send the current or next group of top-level statements to the Python shell and
step. A sequence of top-level statements is a group if they are not separated by
empty lines. Empty lines within each top-level statement are ignored.
If the point is within a statement, send the group around this statement.
Otherwise, go to the top-level statement below point and send the group around this
statement.
C-c C-y W (elpy-shell-send-codecell-and-step)
Send the current code cell to the Python shell and step. A code cell is a piece of
code surrounded by special separator lines; see below. For example, you can insert
two lines starting with ## to quickly send the code in-between.
elpy-shell-codecell-beginning-regexp (Customize Option)
Regular expression for matching a line indicating the beginning of a code cell. By
default, ##.* is treated as a beginning of a code cell, as are the code cell
beginnings in Python files exported from IPython or Jupyter notebooks (e.g., #
<codecell> or # In[1]:).
elpy-shell-cell-boundary-regexp (Customize Option)
Regular expression for matching a line indicating the boundary of a cell (beginning
or ending). By default, ##.* is treated as a cell boundary, as are the boundaries
in Python files exported from IPython or Jupyter notebooks (e.g., # <markdowncell>,
# In[1]:, or # Out[1]:).
Note that elpy-shell-codecell-beginning-regexp must also match the cell boundaries
defined here.
The functions for sending the entire buffer have special support for avoiding accidental
code execution, e.g.:
C-c C-y r (elpy-shell-send-region-or-buffer)
Send the the active region (if any) or the entire buffer (otherwise) to the Python
shell and keep point position.
When sending the whole buffer, this command will also escape any uses of the if
__name__ == '__main__' idiom, to prevent accidental execution of a script. If you
want this to be evaluated, pass a prefix argument with C-u.
Also bound to C-c C-c.
elpy-shell-add-to-shell-history (Customize Option)
If t, Elpy will make the code sent available in the shell history. This allows to
use comint-previous-input (C-up) in the python shell to get back the pieces of code
sent by Elpy.
The list of remaining commands to send code fragments is:
C-c C-y s (elpy-shell-send-top-statement)
C-c C-y S (elpy-shell-send-top-statement-and-go)
C-c C-y f (elpy-shell-send-defun)
C-c C-y F (elpy-shell-send-defun-and-go)
C-c C-y c (elpy-shell-send-defclass)
C-c C-y C (elpy-shell-send-defclass-and-go)
C-c C-y o (elpy-shell-send-group)
C-c C-y O (elpy-shell-send-group-and-go)
C-c C-y w (elpy-shell-send-codecell)
C-c C-y W (elpy-shell-send-codecell-and-go)
C-c C-y R (elpy-shell-send-region-or-buffer-and-go)
C-c C-y b (elpy-shell-send-buffer)
C-c C-y B (elpy-shell-send-buffer-and-go)
C-c C-y C-s (elpy-shell-send-top-statement-and-step)
C-c C-y C-S-S (elpy-shell-send-top-statement-and-step-and-go)
C-c C-y C-f (elpy-shell-send-defun-and-step)
C-c C-y C-S-F (elpy-shell-send-defun-and-step-and-go)
C-c C-y C-c (elpy-shell-send-defclass-and-step)
C-c C-y C-S-C (elpy-shell-send-defclass-and-step-and-go)
C-c C-y C-S-O (elpy-shell-send-group-and-step-and-go)
C-c C-y C-W (elpy-shell-send-codecell-and-step-and-go)
C-c C-y C-r (elpy-shell-send-region-or-buffer-and-step)
C-c C-y C-S-R (elpy-shell-send-region-or-buffer-and-step-and-go)
C-c C-y C-b (elpy-shell-send-buffer-and-step)
C-c C-y C-S-B (elpy-shell-send-buffer-and-step-and-go)
Shell feedback
When package eval-sexp-fu is loaded and eval-sexp-fu-flash-mode is active, the statements
sent to the shell are briefly flashed after running an evaluation command, thereby
providing visual feedback.
elpy-shell-echo-input (Customize Option)
Whenever a code fragment is sent to the Python shell, Elpy prints it in the Python
shell buffer (i.e., it looks as if it was actually typed into the shell). This
behavior can be turned on and off via the custom variable elpy-shell-echo-input and
further customized via elpy-shell-echo-input-cont-prompt (whether to show
continuation prompts for multi-line inputs) and elpy-shell-echo-input-lines-head /
elpy-shell-echo-input-lines-tail (how much to cut when input is long).
elpy-shell-echo-output (Customize Option)
Elpy shows the output produced by a code fragment sent to the shell in the echo
area when the shell buffer is currently invisible. This behavior can be controlled
via elpy-shell-echo-output (never, always, or only when shell invisible). Output
echoing is particularly useful if the custom variable
elpy-shell-display-buffer-after-send is set to nil (the default value). Then, no
window is needed to display the shell (thereby saving screen real estate), but the
outputs can still be seen in the echo area.
elpy-shell-display-buffer-after-send (Customize Option)
Whether to display the Python shell after sending something to it (default nil).
Syntax Checking
Whenever you save a file, Elpy will run a syntax check and highlight possible errors or
warnings inline.
C-c C-n (elpy-flymake-next-error)
C-c C-p (elpy-flymake-previous-error)
You can navigate between any error messages with these keys. The current error will
be shown in the minibuffer.
Elpy uses the built-in Flymake library to find syntax errors on the fly, so see there for
more configuration options.
C-c C-v (elpy-check)
Alternatively, you can run a syntax check on the current file where the output is
displayed in a new buffer, giving you an overview and allowing you to jump to the
errors from there.
With a prefix argument, this will run the syntax check on all files in the current
project.
python-check-command (Customize Option)
To change which command is used for syntax checks, you can customize this option.
By default, Elpy uses the flake8 program, which you have to install separately. The
elpy-config command will prompt you to do this if Elpy can't find the program.
It is possible to create a single virtual env for the sole purpose of installing
flake8 in there, and then simply link the command script to a directory inside your
PATH, meaning you do not need to install the program in every virtual env
separately.
Documentation
Elpy provides a single interface to documentation.
C-c C-d (elpy-doc)
When point is on a symbol, Elpy will try and find the documentation for that
object, and display that. If it can't find the documentation for whatever reason,
it will try and look up the symbol at point in pydoc. If it's not there, either, it
will prompt the user for a string to look up in pydoc.
With a prefix argument, Elpy will skip all the guessing and just prompt the user
for a string to look up in pydoc.
If the autodoc module is enabled (not by default) the documentation is automatically
updated with the symbol at point or the currently selected company candidate.
elpy-autodoc-delay (Customize Option)
The idle delay in seconds until documentation is updated automatically.
Snippets
Elpy uses yasnippet to provide code templates that helps writing common pieces of code
faster. You can access a template by typing a "template key" and hitting TAB to expand
it. You may then be asked to fill some fields in the template, just hit TAB when you are
done to proceed to the next field.
The sequel presents a list of templates provided by Elpy.
Special methods
Elpy provides a large range of templates for special class methods (__init__, __call__,
__add__, ...). To call them, simply type _ followed by the method name (for example
_init) and hit TAB.
Other useful snippets
• enc: Encoding statement
• env: Hashbang statement
• from: Import statement
• pdb: Snippet to run pdb at the current script position
• super: Super statement to call parent methods
• def: Function definition
• class: Class definition
• defs: Class method definition
Debugging
Elpy provides an interface to pdb, the builtin Python debugger. Note that this interface
is only available for Emacs 25 and above.
C-c C-u d (elpy-pdb-debug-buffer)
Run pdb on the current buffer. If no breakpoints has been set using
elpy-pdb-toggle-breakpoint-at-point, the debugger will pause at the beginning of
the buffer. Else, the debugger will pause at the first breakpoint. Once pdb is
started, the pdb commands can be used to step through and look into the code
evaluation.
With a prefix argument C-u, ignore the breakpoints and always pause at the
beginning of the buffer.
C-c C-u b (elpy-pdb-toggle-breakpoint-at-point)
Add (or remove) a breakpoint on the current line. Elpy adds a red circle to the
fringe to indicate the presence of a breakpoint. You can then use
elpy-pdb-debug-buffer to start pdb and pause at each of the breakpoints.
With a prefix argument C-u, remove all the breakpoints.
C-c C-u p (elpy-pdb-break-at-point)
Run pdb on the current buffer and pause at the cursor position.
C-c C-u e (elpy-pdb-debug-last-exception)
Run post-mortem pdb on the last exception.
Testing
Testing is an important part of programming. Elpy provides a central interface to testing,
which allows for a good workflow for tests.
Elpy's test interface is built around Emacs' compilation framework. Elpy will run test
commands as a compilation job, with all the advantages this brings.
C-c C-t (elpy-test)
Start a test run. This uses the currently configured test runner to discover and
run tests. If point is inside a test case, the test runner will run exactly that
test case. Otherwise, or if a prefix argument is given, it will run all tests.
M-x elpy-set-test-runner
This changes the current test runner. Elpy supports the standard unittest discovery
runner, the Django discovery runner, nose, green, py.test and Twisted trial. You
can also write your own, as described in Writing Test Runners.
Note on Django runners: Elpy tries to find manage.py within your project structure.
If it's unable to find it, it falls back to django-admin.py. You must set the
environment variable DJANGO_SETTINGS_MODULE accordingly.
This enables a good workflow. You write a test and use C-c C-t to watch it fail. You then
go to your implementation file, for example using C-u C-c C-f, and make the test pass. You
can use a key bound to recompile (I use <f5> for this) to just re-run that one test. Once
that passes, you can use C-c C-t again to run all tests to make sure they all pass as
well. Repeat.
For an even more automated way, you can use tdd.el, which will run your last compile
command whenever you save a file.
Refactoring
C-c C-e (elpy-multiedit-python-symbol-at-point)
Edit all occurrences of the symbol at point at once. This will highlight all such
occurrences, and editing one of them will edit all. This is an easy way to rename
identifiers.
If the backend does not support finding occurrences (currently only Jedi does), or
if a prefix argument is given, this will edit syntactic occurrences instead of
semantic ones. This can match more occurrences than it should, so be careful. You
can narrow the current buffer to the current function using C-x n d to restrict
where this matches.
Finally, if there is a region active, Elpy will edit all occurrences of the text in
the region.
C-c C-r f (elpy-format-code)
Format code using the available formatter.
This command formats code using the first formatter found amongst yapf , autopep8
and black. If a region is selected, only that region is formatted. Otherwise
current buffer is formatted.
yapf and autopep8 can be configured with style files placed in the project root
directory (determined by elpy-project-root).
Profiling
Elpy allows one to profile python scripts asynchronously using cProfile.
M-x elpy-profile-buffer-or-region
Send the current buffer or region to the profiler and display the result with
elpy-profile-visualizer. The default visualizer is snakeviz, a browser-based
graphical profile viewer that can be installed with pip install snakeviz.
RunSnakeRun (Python-2 only GTK GUI) and pyprof2calltree (uses QCacheGrind or
KCacheGrind for display) are supported alternatives and can be similarly installed
with pip.
Django
Elpy has basic Django support such as parsing either manage.py or django-admin.py (If it
does not find manage.py it falls back to django-admin.py) for command completion
assistance. Can also start runserver automatically and you can give an ip address and
port.
C-c C-x c (elpy-django-command)
Choose what command you'd like to run via django-admin.py or manage.py. Please
note that for compatibility reasons, the shell command will use python (instead of
ipython by default).
C-c C-x r (elpy-django-runserver)
Start the development server command, runserver. Default arguments are 127.0.0.1
for ip address and 8000 for port. These can be changed via
elpy-django-server-ipaddr and elpy-django-server-port.
CONCEPTS
The RPC Process
Elpy works by starting a Python process in the background and communicating with it
through a basic Remote Procedure Call (RPC) interface. Ideally, you should never see this
process and not worry about it, but when things don't work as expected, it's good to know
what's going on in the background.
Every project and virtual env combination gets their own RPC process. You can see them
both in the process list (M-x list-process) as well as in the buffer list (C-x C-b) as
buffers named *elpy-rpc[...]*.
RPC processes are used to provide code completion, documentation and other features. To do
so, they use python packages (jedi, yapf, rope, ...) that are installed in a dedicated
virtualenv (.emacs.d/elpy/rpc-venv by default). Those packages can be updated through the
configuration panel (accessible with M-x elpy-config).
By default, Elpy will also find the library root of the current file and pass that to the
RPC functions. The library root is the directory from which the current file can be
imported.
There are a few options and commands related to the RPC process.
M-x elpy-rpc-restart
Close all running RPC processes. Elpy will re-start them on demand with current
settings.
elpy-rpc-python-command (Customize Option)
The Python interpreter Elpy should use to run the RPC process. This defaults to
"python", which should be correct for most cases.
Please do note that this is not an interactive interpreter, so do not set this to
"ipython", "jupyter" or similar.
As the RPC should be independent of any virtual environment, Elpy will try to use
the system interpreter if it exists. If you wish to use a specific python
interpreter (from a virtual environment for example), set this to the full
interpreter path.
elpy-rpc-virtualenv-path (Customize Option)
Path to the virtualenv used by the RPC.
Can be 'default (create a dedicated virtualenv .emacs.d/elpy/rpc-venv), 'system
(use the system environment), 'current (use the currently active environment), a
virtualenv path or a function returning a virtualenv path.
If the default virtual environment does not exist, it will be created using
elpy-rpc-python-command and populated with the needed packages from
elpy-rpc--get-package-list.
elpy-rpc-large-buffer-size (Customize Option)
The size in character starting from which Elpy will transfer buffer contents via
temporary files instead of via the normal RPC mechanism.
When Elpy communicates with the RPC process, it often needs to tell Python about
the contents of the current buffer. As the RPC protocol encodes all data in JSON,
this can be a bit slow for large buffers. To speed things up, Elpy can transfer
file contents in temporary files, which is a lot faster for large files, but
slightly slower for small ones.
elpy-rpc-pythonpath (Customize Option)
A directory to add to the PYTHONPATH for the RPC process. This should point to the
directory where the elpy module is installed. Usually, there is no need to change
this.
Backends
For introspection and analysis of Python sources, Elpy mainly relies on Jedi, a python
package for static code analysis.
Due to the dynamic nature of python and its minimalist structure syntax, python code can
be difficult to understand in certain situations. Jedi documentation provides some tips
to make jedi job easier.
Virtual Envs
Elpy has full support for Python's virtual envs. Every RPC process is associated with a
specific virtual env and completions are done based on that environment.
Outside of RPC processes, though, it is not easy to have more than one virtual env active
at the same time. Elpy allows you to set a single global virtual env and change it
whenever you like, though.
M-x pyvenv-workon
M-x pyvenv-activate
M-x pyvenv-deactivate
These commands are the main interaction point with virtual envs, mirroring the
normal activate and deactivate commands of virtual envs and the workon command of
virtualenvwrapper.sh.
The pyvenv-workon command will allow auto-completion of existing virtual envs and
also supports virtualenvwrapper's setup hooks to set environment variables.
Elpy won't pollute your Emacs command namespaces, but it might be an idea to create an
alias for the workon command:
(defalias 'workon 'pyvenv-workon)
Modules
As the last concept, Elpy has a number of optional features you can enable or disable as
per your preferences.
elpy-modules (Customize Option)
The list of modules to activate by default. See the section on Writing Modules for
details on how to write your own modules.
EXTENDING ELPY
Writing Modules
Modules are a way of easily extending Elpy with modular extensions. In essence, a module
is a function which is called once to initialize itself globally, then once every time
elpy-mode is enabled or disabled, and also once if elpy is disabled globally.
To achieve this, a module function receives one or more arguments, the first of which is
the command specifier symbol, which can be one of the following:
global-init
Called once, when Elpy is enabled using elpy-enable.
global-stop
Called once, when Elpy is disabled using elpy-disable.
buffer-init
Called in a buffer when elpy-mode is enabled.
buffer-stop
Called in a buffer when elpy-mode is disabled.
To activate a module, the user has to add the function to elpy-modules.
Writing Test Runners
A test runner is a function that receives four arguments, described in the docstring of
elpy-test-at-point. If only the first argument is given, the test runner should find tests
under this directory and run them. If the others are given, the test runner should run the
specified test only, or as few as it can.
Test runners should use an interactive spec of (interactive (elpy-test-at-point)) so they
can be called directly by the user. For their main work, they can use the helper function
elpy-test-run. See the elpy-test-discover-runner for an example.
To make it possible to set the test runner as a file-, directory- or project-local
variable, the function symbol should get the elpy-test-runner property with a value of t.
Running Tests:
You can set up a working environment for Elpy using pip and cask. After installing Cask,
create a new virtual environment and run the setup script in it:
virtualenv ~/.virtualenvs/elpy
source ~/.virtualenvs/elpy/bin/activate
./scripts/setup
You can now run ./scripts/test to run Elpy's test suite.
If you cannot (or do not want to) use virtual environments on your system, you can set the
environment variable ELPY_TEST_DONT_USE_VIRTUALENV to skip tests involving virtual
environments: ELPY_TEST_DONT_USE_VIRTUALENV=t ./scripts/test.
CUSTOMIZATION TIPS
Use flycheck instead of flymake
(when (load "flycheck" t t)
(setq elpy-modules (delq 'elpy-module-flymake elpy-modules))
(add-hook 'elpy-mode-hook 'flycheck-mode))
Enable emacs 26 flymake indicators in an otherwise light modeline
(setq elpy-remove-modeline-lighter t)
(advice-add 'elpy-modules-remove-modeline-lighter
:around (lambda (fun &rest args)
(unless (eq (car args) 'flymake-mode)
(apply fun args))))
See also the associated issue
An alternative to elpy-goto-definition
You may sometimes find when you try to navigate to a function/class definition with
elpy-goto-definition (M-.), that instead of jumping to the definition, you get the message
"No definition found". If you see this error often (because of the nature of the code you
work on), you can use the following function instead of/in addition to
elpy-goto-definition:
(defun elpy-goto-definition-or-rgrep ()
"Go to the definition of the symbol at point, if found. Otherwise, run `elpy-rgrep-symbol'."
(interactive)
(ring-insert find-tag-marker-ring (point-marker))
(condition-case nil (elpy-goto-definition)
(error (elpy-rgrep-symbol
(concat "\\(def\\|class\\)\s" (thing-at-point 'symbol) "(")))))
This function will try to find the definition of the symbol at point using
elpy-goto-definition, but will do elpy-rgrep-symbol instead, if the former function fails
to return a result. You can bind this function to the key combination of your choice, or
you can bind it to M-. to use it as a replacement for the the default goto-definition
function:
(define-key elpy-mode-map (kbd "M-.") 'elpy-goto-definition-or-rgrep)
Enable full font locking of inputs in the python shell
(advice-add 'elpy-shell--insert-and-font-lock
:around (lambda (f string face &optional no-font-lock)
(if (not (eq face 'comint-highlight-input))
(funcall f string face no-font-lock)
(funcall f string face t)
(python-shell-font-lock-post-command-hook))))
(advice-add 'comint-send-input
:around (lambda (f &rest args)
(if (eq major-mode 'inferior-python-mode)
(cl-letf ((g (symbol-function 'add-text-properties))
((symbol-function 'add-text-properties)
(lambda (start end properties &optional object)
(unless (eq (nth 3 properties) 'comint-highlight-input)
(funcall g start end properties object)))))
(apply f args))
(apply f args))))
See details in https://github.com/jorgenschaefer/elpy/issues/1428 and
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=32344.
FAQ
Q: Can I tell elpy not to load one of the minor modes it enables by default?
A: You can simply remove the appropriate symbol from elpy-modules.
Q: How do I make Elpy work well with org-mode?
A: You can try the following customization by @mankoff:
(setq python-shell-interpreter "ipython"
python-shell-interpreter-args "--pylab=osx --pdb --nosep --classic"
python-shell-prompt-regexp ">>> "
python-shell-prompt-output-regexp ""
python-shell-completion-setup-code "from IPython.core.completerlib import module_completion"
python-shell-completion-module-string-code "';'.join(module_completion('''%s'''))\n"
python-shell-completion-string-code "';'.join(get_ipython().Completer.all_completions('''%s'''))\n")
See #191 for a discussion and background.
Q: Can I get documentation as pop-ups next to the completion pop-up?
A: Not by default with company-mode, but there’s expez’ excellent company-quickhelp
package you can install for this feature. It’s available from MELPA.
Q: How to solve company, yasnippet conflicts?
A: Add this snippet to your emacs configuration to avoid that.
(defun company-yasnippet-or-completion ()
"Solve company yasnippet conflicts."
(interactive)
(let ((yas-fallback-behavior
(apply 'company-complete-common nil)))
(yas-expand)))
(add-hook 'company-mode-hook
(lambda ()
(substitute-key-definition
'company-complete-common
'company-yasnippet-or-completion
company-active-map)))
Q: How do I install development version of elpy?
A: Remove existing elpy if you already installed it.
rm -rf ~/.emacs.d/elpa/elpy*
Install dependencies
(package-install 'company)
(package-install 'yasnippet)
(package-install 'pyvenv)
(package-install 'highlight-indentation)
(package-install 's)
Get latest code from github
mkdir ~/Projects
cd ~/Projects
git clone https://github.com/jorgenschaefer/elpy
Add the following to your ~/.emacs.d/init.el or ~/.emacs:
(add-to-list 'load-path "~/Projects/elpy")
(load "elpy" nil t)
(elpy-enable)
To update, run git pull --rebase, M-x load-library RET elpy RET and M-x elpy-rpc-reload.
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AUTHOR
Jorgen Schäfer
COPYRIGHT
2020, Jorgen Schäfer