Is there an equivalent function to eval-print-last-sexp for comint derived modes in emacs?
Specifically, I'm using python-mode (with elpy) and am looking for a way to send the contents of a region to the Python process and then print the results on the next line of the python script I'm working in.
Printing the results to the Messages buffer would be acceptable as well, however the behavior of eval-print-last-sexp would be preferred.
I'm running Emacs 25.1.1 and elpy 1.13.0.
It would depend on the comint-derived mode, since you would need to redirect the process output. Different modes have different methods of interacting with inferior processes. Python mode already has a function to do this, python-shell-send-string-no-output (other modes have similar functions, but you would need to search for them).
I'm not sure how exactly you want to define a sexp for python, but here is an example of sending the current line, with output like eval-print-last-sexp.
(defun python-eval-print-last-sexp ()
"Print result of evaluating current line into current buffer."
(interactive)
(let ((res (python-shell-send-string-no-output
;; modify to get a different sexp
(buffer-substring (line-beginning-position)
(line-end-position))))
(standard-output (current-buffer)))
(when res
(terpri)
(princ res)
(terpri))))
elpy-shell-send-statement from the Emacs Python Development Environment.
In - Python, inside the the IDLE, in the File Editor Window,
How do you run just a selected single line of code in the script, without having the rest of the lines of the program being runned ?
You'll have to run your line of code form command line:
With the -c (command) argument (assuming your file is named foo.py):
$ python -c 'import foo; print foo.hello()'
You can select and copy a single statement in an Idle editor (or anywhere else, for that matter), switch to the Idle Shell, and paste on the line with the >>> prompt as the bottom. (You can hit to get a clean prompt.) Then hit return just as it you had entered into the shell directly. This works for multiline statements. Being able to do this with a menu selection, hotkey, or right-click selection is on my todo list, as you are not the first to ask about this.
Basically, what we call "debugger" should be fulfilled your requirement. Many IDEs are provided "debugger tools" including IDLE. To use a debugger tool you can just simply
add break lines (any lines of code you want a program to stop while program is running),
explore your variables (when program is stop you can print out values of your variables at that time)
Click/type step to go to the next breakpoint.
This is just a roughly procedure that should be fit to your requirement.
see more: debug
From what I have read, there are two ways to debug code in Python:
With a traditional debugger such as pdb or ipdb. This supports commands such as c for continue, n for step-over, s for step-into etc.), but you don't have direct access to an IPython shell which can be extremely useful for object inspection.
Using IPython by embedding an IPython shell in your code. You can do from IPython import embed, and then use embed() in your code. When your program/script hits an embed() statement, you are dropped into an IPython shell. This allows the full inspection of objects and testing of Python code using all the IPython goodies. However, when using embed() you can't step-by-step through the code anymore with handy keyboard shortcuts.
Is there any way to combine the best of both worlds? I.e.
Be able to step-by-step through your code with handy pdb/ipdb keyboard shortcuts.
At any such step (e.g. on a given statement), have access to a full-fledged IPython shell.
IPython debugging as in MATLAB:
An example of this type of "enhanced debugging" can be found in MATLAB, where the user always has full access to the MATLAB engine/shell, and she can still step-by-step through her code, define conditional breakpoints, etc. From what I have discussed with other users, this is the debugging feature that people miss the most when moving from MATLAB to IPython.
IPython debugging in Emacs and other editors:
I don't want to make the question too specific, but I work mostly in Emacs, so I wonder if there is any way to bring this functionality into it. Ideally, Emacs (or the editor) would allow the programmer to set breakpoints anywhere on the code and communicate with the interpreter or debugger to have it stop in the location of your choice, and bring to a full IPython interpreter on that location.
What about ipdb.set_trace() ? In your code :
import ipdb; ipdb.set_trace()
update: now in Python 3.7, we can write breakpoint(). It works the same, but it also obeys to the PYTHONBREAKPOINT environment variable. This feature comes from this PEP.
This allows for full inspection of your code, and you have access to commands such as c (continue), n (execute next line), s (step into the method at point) and so on.
See the ipdb repo and a list of commands. IPython is now called (edit: part of) Jupyter.
ps: note that an ipdb command takes precedence over python code. So in order to write list(foo) you'd need print(list(foo)), or !list(foo) .
Also, if you like the ipython prompt (its emacs and vim modes, history, completions,…) it's easy to get the same for your project since it's based on the python prompt toolkit.
You can use IPython's %pdb magic. Just call %pdb in IPython and when an error occurs, you're automatically dropped to ipdb. While you don't have the stepping immediately, you're in ipdb afterwards.
This makes debugging individual functions easy, as you can just load a file with %load and then run a function. You could force an error with an assert at the right position.
%pdb is a line magic. Call it as %pdb on, %pdb 1, %pdb off or %pdb 0. If called without argument it works as a toggle.
(Update on May 28, 2016) Using RealGUD in Emacs
For anyone in Emacs, this thread shows how to accomplish everything described in the OP (and more) using
a new important debugger in Emacs called RealGUD which can operate with any debugger (including ipdb).
The Emacs package isend-mode.
The combination of these two packages is extremely powerful and allows one to recreate exactly the behavior described in the OP and do even more.
More info on the wiki article of RealGUD for ipdb.
Original answer:
After having tried many different methods for debugging Python, including everything mentioned in this thread, one of my preferred ways of debugging Python with IPython is with embedded shells.
Defining a custom embedded IPython shell:
Add the following on a script to your PYTHONPATH, so that the method ipsh() becomes available.
import inspect
# First import the embed function
from IPython.terminal.embed import InteractiveShellEmbed
from IPython.config.loader import Config
# Configure the prompt so that I know I am in a nested (embedded) shell
cfg = Config()
prompt_config = cfg.PromptManager
prompt_config.in_template = 'N.In <\\#>: '
prompt_config.in2_template = ' .\\D.: '
prompt_config.out_template = 'N.Out<\\#>: '
# Messages displayed when I drop into and exit the shell.
banner_msg = ("\n**Nested Interpreter:\n"
"Hit Ctrl-D to exit interpreter and continue program.\n"
"Note that if you use %kill_embedded, you can fully deactivate\n"
"This embedded instance so it will never turn on again")
exit_msg = '**Leaving Nested interpreter'
# Wrap it in a function that gives me more context:
def ipsh():
ipshell = InteractiveShellEmbed(config=cfg, banner1=banner_msg, exit_msg=exit_msg)
frame = inspect.currentframe().f_back
msg = 'Stopped at {0.f_code.co_filename} at line {0.f_lineno}'.format(frame)
# Go back one level!
# This is needed because the call to ipshell is inside the function ipsh()
ipshell(msg,stack_depth=2)
Then, whenever I want to debug something in my code, I place ipsh() right at the location where I need to do object inspection, etc. For example, say I want to debug my_function below
Using it:
def my_function(b):
a = b
ipsh() # <- This will embed a full-fledged IPython interpreter
a = 4
and then I invoke my_function(2) in one of the following ways:
Either by running a Python program that invokes this function from a Unix shell
Or by invoking it directly from IPython
Regardless of how I invoke it, the interpreter stops at the line that says ipsh(). Once you are done, you can do Ctrl-D and Python will resume execution (with any variable updates that you made). Note that, if you run the code from a regular IPython the IPython shell (case 2 above), the new IPython shell will be nested inside the one from which you invoked it, which is perfectly fine, but it's good to be aware of. Eitherway, once the interpreter stops on the location of ipsh, I can inspect the value of a (which be 2), see what functions and objects are defined, etc.
The problem:
The solution above can be used to have Python stop anywhere you want in your code, and then drop you into a fully-fledged IPython interpreter. Unfortunately it does not let you add or remove breakpoints once you invoke the script, which is highly frustrating. In my opinion, this is the only thing that is preventing IPython from becoming a great debugging tool for Python.
The best you can do for now:
A workaround is to place ipsh() a priori at the different locations where you want the Python interpreter to launch an IPython shell (i.e. a breakpoint). You can then "jump" between different pre-defined, hard-coded "breakpoints" with Ctrl-D, which would exit the current embedded IPython shell and stop again whenever the interpreter hits the next call to ipsh().
If you go this route, one way to exit "debugging mode" and ignore all subsequent breakpoints, is to use ipshell.dummy_mode = True which will make Python ignore any subsequent instantiations of the ipshell object that we created above.
You can start IPython session from pudb and go back to the debugging session as you like.
BTW, ipdb is using IPython behind the scenes and you can actually use IPython functionality such as TAB completion and magic commands (the one starts with %). If you are OK with ipdb you can start it from IPython using commands such as %run and %debug. ipdb session is actually better than plain IPython one in the sense you can go up and down in the stack trace etc. What is missing in ipdb for "object inspection"?
Also, python.el bundled with Emacs >= 24.3 has nice ipdb support.
Looks like the approach in #gaborous's answer is deprecated.
The new approach seems to be:
from IPython.core import debugger
debug = debugger.Pdb().set_trace
def buggy_method():
debug()
Prefixing an "!" symbol to commands you type in pdb seems to have the same effect as doing something in an IPython shell. This works for accessing help for a certain function, or even variable names. Maybe this will help you to some extent. For example,
ipdb> help(numpy.transpose)
*** No help on (numpy.transpose)
But !help(numpy.transpose) will give you the expected help page on numpy.transpose. Similarly for variable names, say you have a variable l, typing "l" in pdb lists the code, but !l prints the value of l.
You can start IPython from within ipdb.
Induce the ipdb debugger1:
import idpb; ipdb.set_trace()
Enter IPython from within in the ipdb> console2:
from IPython import embed; embed()
Return to the ipdb> console from within IPython:
exit
If you're lucky enough to be using Emacs, things can be made even more convenient.
This requires using M-x shell. Using yasnippet and bm, define the following snippet. This will replace the text ipdb in the editor with the set-trace line. After inserting the snippet, the line will be highlighted so that it is easily noticeable and navigable. Use M-x bm-next to navigate.
# -*- mode: snippet -*-
# name: ipdb
# key: ipdb
# expand-env: ((yas-after-exit-snippet-hook #'bm-toggle))
# --
import ipdb; ipdb.set_trace()
1 All on one line for easy deletion. Since imports only happen once, this form ensures ipdb will be imported when you need it with no extra overhead.
2 You can save yourself some typing by importing IPython within your .pdbrc file:
try:
from IPython import embed
except:
pass
This allows you to simply call embed() from within ipdb (of course, only when IPython is installed).
Did you try this tip?
Or better still, use ipython, and call:
from IPython.Debugger import Tracer; debug_here = Tracer()
then you can just use
debug_here()
whenever you want to set a breakpoint
the right, easy, cool, exact answer for the question is to use %run macro with -d flag.
In [4]: run -d myscript.py
NOTE: Enter 'c' at the ipdb> prompt to continue execution.
> /cygdrive/c/Users/mycodefolder/myscript.py(4)<module>()
2
3
----> 4 a=1
5 b=2
One option is to use an IDE like Spyder which should allow you to interact with your code while debugging (using an IPython console, in fact). In fact, Spyder is very MATLAB-like, which I presume was intentional. That includes variable inspectors, variable editing, built-in access to documentation, etc.
If you type exit() in embed() console the code continue and go to the next embed() line.
The Pyzo IDE has similar capabilities as the OP asked for. You don't have to start in debug mode. Similarly to MATLAB, the commands are executed in the shell. When you set up a break-point in some source code line, the IDE stops the execution there and you can debug and issue regular IPython commands as well.
It does seem however that step-into doesn't (yet?) work well (i.e. stopping in one line and then stepping into another function) unless you set up another break-point.
Still, coming from MATLAB, this seems the best solution I've found.
From python 3.2, you have the interact command, which gives you access to the full python/ipython command space.
Running from inside Emacs' IPython-shell and breakpoint set via pdb.set_trace() should work.
Checked with python-mode.el, M-x ipython RET etc.
Developing New Code
Debugging inside IPython
Use Jupyter/IPython cell execution to speed up experiment iterations
Use %%debug for step through
Cell Example:
%%debug
...: for n in range(4):
...: n>2
Debugging Existing Code
IPython inside debugging
Debugging a broken unit test: pytest ... --pdbcls=IPython.terminal.debugger:TerminalPdb --pdb
Debugging outside of test case: breakpoint(), python -m ipdb, etc.
IPython.embed() for full IPython functionality where needed while in the debugger
Thoughts on Python
I agree with the OP that many things MATLAB does nicely Python still does not have and really should since just about everything in the language favors development speed over production speed. Maybe someday I will contribute more than trivial bug fixes to CPython.
https://github.com/ipython/ipython/commit/f042f3fea7560afcb518a1940daa46a72fbcfa68
See also Is it possible to run commands in IPython with debugging?
If put import ipdb; ipdb.set_trace() at cell outside function, it will occur error.
Using %pdb or %debug, you can only see the filnal error result. You cannot see the code doing step by step.
I use following skill:
%%writefile temp.py
.....cell code.....
save the code of cell to file temp.py.
and then
%run -i -d temp.py, it will run the cell code by pdb .
-i: run the file in IPython’s namespace instead of an empty one.
-d: run your program under the control of pdb, the Python debugger.
I apologize if I use the incorrect terminology here, I've only been using emacs for a few months.
I just reinstalled Aquamacs on a macbook that I reformatted and am having the oddest problem.
I open a .py file, and use C-c ! to open a python shell. So I have (as expected), the .py file in the top window and the python shell in the bottom window.
If I then run C-c C-c (py-execute-buffer) in the .py file, the two windows swap positions. I mean, the .py file buffer opens in the bottom window in a new buffer, while the python shell opens in the top window in a new buffer. So basically, they swap positions. Repeatedly using C-c C-c swaps the windows back again... so they're shuffling positions. Also, both windows (top and bottom) have both buffers (.py file and python shell) in tabs.
I've not made any modifications to the default settings yet, and I've gotten the problem with both 2.3a and 2.3 (2.3 was on the machine previously and didn't have this problem, so I tried rolling back... to no avail).
Does anyone know how to stop this behavior? Thanks in advance!
Add the following to your Emacs init file in Aquamacs to prevent it from swapping the buffers around:
(defadvice py-execute-buffer
(around keep-buffers-same activate)
"Don't swap buffers in Aquamacs."
(save-window-excursion
ad-do-it))
You can also try adding the following to your emacs init file:
(setq py-split-windows-on-execute-p nil)
This will prevent the current window from splitting after you run any py-execute-*. (This also means that the python shell won't show up if it isn't already in one of your windows.)
i don't use Aquamacs and couldn't reproduce your described behaviour, however, try this code to toggle either of the windows as 'dedicated'. locking windows to buffers was the first thing i wanted to do when getting up and running with emacs. maybe this will help you here.
add the code to your '.emacs', then either 'mark' (select) the region 'S-< key-down >' and then 'M-x eval-region' to evaluate it ..or save and restart emacs.
(global-set-key [pause] 'window-dedication-toggle)
(defun window-dedication-toggle (&optional window force quiet)
"toggle or ensure the 'dedicated' state for a window"
(interactive)
(let* ((toggle t) (window (if window window (selected-window))) (dedicated (window-dedicated-p window)))
(cond ((equal force "on") (setq toggle (eq dedicated nil)))
((equal force "off") (setq toggle (eq dedicated t))))
(if toggle (progn
(setq dedicated (not dedicated))
(set-window-dedicated-p window dedicated)
(if (not quiet)
(message "window %sdedicated to %s" (if (not dedicated) "no longer " "") (buffer-name)))))))
In python-mode, there is a function called py-execute-region which sends a highlighted region of code to the Python buffer for evaluation. After evaluation, the cursor is in the Python buffer, but I would prefer that it remain in the script buffer so I can continue producing more code. I wrote a simple advising function:
(defadvice py-execute-region
(after py-execute-region-other-window activate)
""" After execution, return cursor to script buffer """
(other-window 1)
)
But this does not do anything at all. I've tried other variants like using 'around' rather than 'after'; setting a variable to the script buffer name and then pop-to-buffer to that buffer and stuff like that. No success! I wonder if the mechanics of this is obvious to someone... Thanks!
In this case the solution appears to be
(custom-set-variables
'(py-shell-switch-buffers-on-execute nil))
Use around-advice to wrap the function in a call to
save-window-excursion, which will restore the previous window
configuration after the command completes.
(defadvice py-execute-region
(around preserve-window-configuration activate)
"After execution, return cursor to script buffer"
(save-window-excursion ad-do-it))
Keep in mind, though, that if the Python buffer wasn't already shown,
it will still be hidden after the command completes. To remedy that,
you can add another piece of advice to call switch-to-buffer-other-window at the
end:
(defadvice py-execute-region
(after show-pybuf-other-window activate)
"After execution, show the python buffer in another window."
(switch-to-buffer-other-window "[PYTHON BUFFER NAME]"))
Also, make sure you don't use """triple quotes""" in elisp. I don't
think they work.
What you have there works fine for me. And it should auto-activate, so a separate activation should be unnecessary. However, you do need to de-active and re-activate advice for changes to take effect:
1) define and activate advice
2) it doesn't do what you want, so change the advice
3) deactivate it: (ad-deactivate 'py-execute-region)
4) reactivate it: (ad-activate 'py-execute-region)
Step 4 should pick up the changes you made in step 2. Alternately, you can change the code in step 2 and then just re-evaluate the code in step 4 (assuming the activate flag is set).
I haven't actually tried this out, but I did do something similar for find-file, and over there I needed to call interactive before calling other-window. I actually have no real idea of Emacs Lisp, but this may work.
(defadvice py-execute-region
(after py-execute-region-other-window activate)
(interactive)
(other-window 1)
)