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https://github.com/abo-abo/lpy

Minimal Python IDE for GNU Emacs
https://github.com/abo-abo/lpy

emacs ide python

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Minimal Python IDE for GNU Emacs

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README 

        
* lpy



Deceptively minimalistic Python IDE for GNU Emacs.



* Setup

Install from MELPA and enable =lpy-mode=.



* Introduction

Q: How many keys does it take to define/redefine a Python function?

A: One - ~e~.



** Arrow navigation

Q: Does this also apply to classes, import statements, for loops and

plain one liners?

A: Of course.



Q: How many keys does it take to move to the next Python function?

A: One - ~j~.



Q: Does this also apply to classes, import statements, for loops and

plain one liners?

A: Of course.



Q: So, how do I eval a statement, move to the second statement, and

eval the second statement?

A: ~eje~.



Q: How to move back to the first statement?

A: ~k~.



Q: How do I descent into a compound statement, like =def=?

A: ~l~.



Q: How do I ascent back?

A: ~h~.



Q: Back to eval, how do I eval something that's not a compound

statement?

A: Mark as much legal code as you like with a region and press ~e~.



Q: Any shortcut for marking a symbol in order to eval it?

A: ~M-m~.



** Semantic navigation

Q: How can I select a top-level symbol in the current file?

A: ~g~.



Q: How do I follow to the current symbol's definition?

A: ~M-.~.



Q: How do I go back from there?

A: =M-,=.



Q: Does =M-,= also bring me back after ~g~?

A: Yes.



** Eval in more detail

Q: Where do I see the result of the eval?

A: In the minibuffer.



Q: What if the result of the operation is =None=?

A: Then =(ok)= is printed to confirm that the operation went through.



Q: What if an uncaught exception is thrown?

A: The exception will be displayed in the minibuffer, highlighted in

red.



Q: Is it possible to be productive without ever seeing the REPL

buffer?

A: Yes.



Q: How do I see the REPL buffer?

A: ~C-c C-z~.



Q: Can I have more than one REPL session?

A: Yes, use ~xp~ to select session or start a new one.



Q: Does pressing ~e~ on a variable assignment output nothing because the

result is =None=?

A: No, magic is used to make it print the new value of the variable.



Q: Where else is ~e~ magical?

A: ~e~ on  =__file__= will print the actual file name.



Q: Any more?

A: ~e~ on a single line =return= statement will print the return result.



Q: How do I insert the result of the eval into the buffer?

A: ~E~.



Q: How do I insert the result of the eval into the buffer as a

comment?

A: ~2e~.



Q: Howto easily select things to eval?

A: ~M-m~ to get into special. Then ~+~ and ~-~ to expand/shrink selection with =expand-region=.



** Debugging

Q: How do I step into an expression?

A: ~xj~.



Q: Where does this work?

A: Function or method call, possibly with the result being assigned to

a variable.



Q: What does that do exactly?

A: Evaluate the function arguments, jump to the function definition,

and store the function arguments into global variable with appropriate

names.



Q: So if all I have is =sys.argv= I can use ~xj~ (combined with ~j~, ~l~ and

~e~) to step into my program as deep as I want?

A: Yes.



Q: What if I just want to place a breakpoint to speed things up?

A: To place a breakpoint, throw any exception. Then, enter

=lp.pm()= into the REPL.



Q: =lp.pm()= sounds weird, how can I see how it works?

A: Enter into the REPL: =os.path.realpath(42)= which will raise an

exception a few functions down the line. Then enter =lp.pm()=.



Q: Wait, so this is like =pdb=?

A: Yes, very similar.



Q: So why go through the trouble?

A: To get global variable context and proceed with ~e~ and ~j~.



Q: Got it. Anyway, I see =File "/usr/lib/python2.7/posixpath.py",

line 61, Frame [3/3]:=, what does it mean?

A: =realpath= called =_joinrealpath=, which called =isabs=, which raised an

Exception.



Q: Three functions (=realpath=, =_joinrealpath=, and =isabs=), that's what

3/3 means. And I'm in =isabs= now?

A: Yes.



Q: How do I open the source code for =isabs=?

A: It's a link: use the mouse or =ace-link= or =next-error=.



Q: I'm at the definition of =isabs= now, was its argument value stored

somewhere?

A: Yes, if you eval =s=, you get =42= - the value that propagated from

=os.path.realpath(42)=.



Q: =isabs= is boring. How do I go up the stack?

A: Enter =up= into the REPL.



Q: I entered up, and now the frame is 2/3 and

I'm at =def _joinrealpath(path, rest, seen)=. Does this mean I can eval

=path=, =rest=, and =seen= since they were propagated from the

=os.path.realpath(42)= call?

A: Yes.



Q: And entering =up= again will bring me to 1/3 and =realpath=?

A: Yes.



Q: How do I go back down stack?

A: Enter =dn=.



** Notebooks

Q: Is this like IPython?

A: Yes.



Q: But it's different how?

A: You use Emacs instead of a browser, and the cells are

self-contained in comments.



Q: Sounds nice, but I'm not sold yet?

A: It's like Org-mode embedded in Python code.



Q: So I can fold / unfold each cell?

A: Yes.



Q: And eval/reeval it with ~e~?

A: Yes.



Q: How about organizing cells in a hierarchy?

A: Also possible.



Q: And ~e~ works on the hierarchy as well?

A: Yes.



Q: Are cells actually called different or something?

A: Yes, they're outlines.



Q: How do I make an outline named =Includes=?

A: Enter =#* Includes=.



Q: And like in Org-mode, the amount of stars is that outline's level?

A: Yes.



Q: Do ~M-left~ and ~M-right~ work like in Org-mode for promotion/demotion?

A: Yes.



Q: How to fold/unfold an outline?

A: ~i~.



Q: How do I fold/unfold all outlines?

A: ~I~.



Q: How do I make a table of contents?

A: ~2I~.



Q: When I press ~e~ on an outline it evaluates itself and the result is

echoed; how do I make the result insert itself into the buffer

instead?

A: End the outline name in =:= (semicolon)



Q: How do I clean up all inserted results?

A: ~M-x~ =lpy-clean=.



Q: Any more neat stuff about outlines?

A: Yes, outlines are structured statements and parents to the

top-level statements.



Q: So ~j~ / ~k~ and ~h~ / ~l~, and even ~e~ treat outlines as statements? Neat.

A: Yeah.



** Completion

Q: How do I get completion at point?

A: Press ~C-M-i~.



Q: Is this static completion or does it depend on the REPL state?

A: Both. The static one is more convenient and is tried first. But the

dynamic one is very reliable, since it knows exactly on which type of

object you're operating.



Q: But dynamic completion won't work unless my current object has a

value in the REPL?

A: Correct.



Q: What's used for static completion?

A: Jedi.



** Inline hints

Q: How do I look up the function arguments of the current function?

A: Toggle ~C-2~.



Q: What about the docstring?

A: Toggle ~C-1~.