Develop Reference

Python indentation in Spacemacs with hard tabs is off

Let me preface by saying that I am a relatively new emacs/spacemacs convert from vim, so my my knowledge is still pretty basic.
I have spacemacs set up with the python layer, with the additional package of dtrt-indent listed in dotspacemacs-additional-packages. And setting
(dtrt-indent-mode t)
in the dotspacemacs/user-config. I need the dtrt-indent as I am working on a few projects (in python and lua) where I am not the one who sets the indentation rules.
This configuration works fine for python files with soft-tabs of varying length. This configuration also works for lua files that have hard tabs.
When I open a python file indented with hard tabs something seems to get messed up, it appears to think that the indentation is two hard tabs. Meaning, if I have code like this (pretend that the 4 spaces are tabs):
def func():| <--- Cursor
print 'line'
and press enter, I get:
def func():
| <--- Cursor
print 'line'
The status line prints dtrt-indent's message saying:
Note: indent-tabs-mode adjusted to t
Note: As stated I'm pretty new at this, and my spacemacs configuration is pretty sparse. There is nothing else in my user-config, I have not custom layers, I don't even have any additional packages other than dtrt-indent.
EDIT:
python-indent-offset is set to 8
indent-tabs-mode is set to t
tab-width is set to 4

Try M-x whitespace-mode and repeat this experiment. What do you see? Did you indent with spaces or with tabs?
I'm guessing you'll see something like this:
def·func():
········
» print·'line'
This would mean you have python-indent-offset set to 8, indent-tabs-mode set to nil (aka indent with spaces), and tab-width set to 4.
If that's not the case, what are the values of those variables (C-h v python-indent-offset, etc.)?
If that is the case, you can fix the problem by running
(setq-default python-indent-offset 4)

How to find and replace all tabs with spaces in idle

I have an invisible expected an indented block error, which is likely caused by me using tabs instead of spaces.
When I open the "find/replace" window and try to enter TAB in the find field IDLE unsurprisingly just skips to the replace field.
How do I do this?
Final update:
Thank you for all answers, much appreciated. My problem was that python wants the function comments to be indented too, that is
def imdheladumb():
"""
I'm dum as hel
"""
does not work, it needs to be
def imdheladumb():
"""
I'm dum as hel
"""

IDLE doesn't let you search to literal tab characters. You can paste one into the search box (as suggested by will), but it will never match anything.
However, it does let you do regular expression searches, and the regular expression \t will match a literal tab. So, turn on the Regular expression checkbox, and put '\t in the Find: box, and 4 or 8 spaces (as appropriate) in the Replace: box.
But, as will suggested, it's better to use IDLE's features instead of trying to do things manually: Select the block of code with tabbed (or inconsistent) indentation, go to the Format menu, and select Untabify Region. (Or just hit control-6.) If the tabs were inserted with an editor that uses 4-space tabs, you may need to first use New Indent Width and change it to 4, then Untabify Region.
IDLE doesn't have any code to guess what your tab size was when you wrote the inconsistent code. The only editor I know of that does is emacs. If you just open the file in emacs, it will try to guess your settings, and then you can select the whole buffer and untabify-region. If it guessed right, you're golden; if it guessed wrong, don't save the buffer, because now it'll be even harder to fix. (If you're one of the 3 people in the world who knows how to read emacs lisp but doesn't like emacs, you could look through the python-mode.el source and see how it does its magic.)

A generic way to do this is to just copy a tab character from the document (or just do one in any random text editor and copy it) and then put that into the field.
You could try putting \t in there, but that only works in some editors.
Most IDEs have a function to automatically replace tabs with a predefined number of spaces. I suggest turning that on...
EDIT: doing a standard find and replace could be dangerous if you're using tabs somewhere else for any reason.
If you look here, there's an option called "tabify region". That might be more interesting for you.

There should be an app for that. ;)
If you enjoy overkill, what about running your code through a regular expression like:
re.sub('\t', '\s\s\s\s', yourCode)

For those people having the problem, the new version of VSCode can solve this easily.
Click on Tab Sizes at the bottom of the page.
Select Convert Indentation to Spaces from the "Select Action" menu that pops up.

^H ^? in python

Some terminals will send ^? as backspace, some other terminals will send ^H.
Most of the terminals can be configured to change their behavior.
I do not want to deal with all the possible combinations but I would like to accept both ^? and ^H as a backspace from python.
doing this
os.system("stty erase '^?'")
I will accept the first option and with
os.system("stty erase '^H'")
I will accept the second one but the first will be no longer available.
I would like to use
raw_input("userinput>>")
to grab the input.
The only way I was able to figure out is implementing my own shell which works not on "raw based input" but on "char based input".
Any better (and quicker) idea?

The built-in function raw_input() (or input() in Python 3) will automatically use the readline library after importing it. This gives you a nice and full-feautured line editor, and it is probably your best bet on platforms where it is available, as long as you don't mind Readline having a contagious licence (GPL).

I don't know your question exactly. IMO, you need a method to read some line-based text(including some special character) from console to program.
No matter what method you use, if read this character have special mean in different console, you should confront a console(not only system-specific, but also console-specific) question, all text in console will be store in buffer first, and then show in screen, finally processed and send in to your program. Another way to surround this problem is to use a raw line-obtaining console environment.
You can add a special method(a decorator) to decorate the raw_input() or somewhat input method to process special word.
After solved that question
using this snippet can deal with input,:
def pre():
textline=raw_input()
# ^? should replace to the specific value.
textline.replace("^?","^H")
return textline
To be faster, maybe invoke some system function depend on OS is an idea. But in fact, IO in python is faster enough for common jobs.

To fix ^? on erase do stty erase ^H

indent python file (with pydev) in eclipse

I'm a newbie in eclipse. I want to indent all the lines of my code and formatting the open file by pressing a shortcut or something like that...
I know the CTRL+SHIFT+F (as it actually doesn't work in pydev!!)
I've been searching for hours with no success. Is there any way to do that in eclipse. kind of like CTRL+K,D in visual studio, which formats and indents all the source code lines automatically?

If you want to change from 2 space to 4 space indentation (for instance), use "Source->Convert space to tab" with 2 spaces, then "Soruce->Convert tab to space" with 4 spaces.

I ... don't think this question makes sense. Indentation is syntax in Python. It doesn't make sense to have your IDE auto-indent your code. If it's not indented properly already, it doesn't work, and the IDE can't know where your indentation blocks begin and end. Take, for example:
# Valid Code
for i in range(10):
b = i
for j in range(b):
c = j
# Also Valid Code.
for i in range(10):
b = i
for j in range(b):
c = j
There's no possible way that the IDE can know which of those is the correct version, or what your intent is. If you're going to write Python code, you're going to have to learn to manage the indentation. There's no way to avoid it, and expecting the IDE to magically clean it up and still get the desired result out of it is pretty much impossible.
Further example:
# Valid Code.
outputData = []
for i in range(100):
outputData.append(str(i))
print ''.join(outputData)
# Again, also valid code, wildly different behavior.
outputData = []
for i in range(100):
outputData.append(str(i))
print ''.join(outputData)
The first will produce a list of strings, then print the joined result to the console 1 time. The second will still produce a list of strings, but prints the cumulative joined result for each iteration of the loop - 100 print statements. The two are both 100% syntactically correct. There's no problem with them. Either of them could be what the developer wanted. An IDE can't "know" which is correct. It could, very easily incorrectly change the first version to the second version. Because the Language uses Indentation as Syntax, there is no way to configure an IDE to perform this kind of formatting for you.

Although auto-indentation is not a feature of PyDev because of the language design you should be able to indent with a simple tab. Just select the lines you want to indent and press Tab. If you want to unindent lines you have to press Shift+Tab.
Thats all.

It is much easier:
Select multiple lines
Press Tab to indent (move right), Shift + Tab to unindent (move left) all selected
lines.

Indentation is syntactically significant; consider the difference between
for i in range(5):
print i
print "done"
and
for i in range(5):
print i
print "done"
However, it certainly makes sense for the IDE to be able to normalize the existing indentation (e.g. apply a consistent number of spaces/tabs at each level).
Currently PyDev does not support such a feature; Pydev author Fabioz at one point expressed interest in adding it in the future and indicated that for now you can use the supplied reindent.py script to do it.

Obviously this is only for Pydev, but I've worked out that you can get the very useful functions "Shift Right" and "Shift Left" (mapped by default to CTRL + ALT + . and CTRL + ALT + ,) to become useful by changing their keybindings to "Pydev Editor Scope" from "Pydev View". This effectively indents/dedents all lines that you've selected as much as you'd like

I think that what you're looking for is some kind of shortcut in Eclipse/PyDev so that the selected code can be idented all at once. Just like when you create a new "if" or a "for" loop above a block of code and then need to rearrange the identation. The IDLE Editor has the "Ctrl + ]" shortcut that works exactly that way. It seems that the PyDev in Eclipse doesnt have something like that as far as I know.

One can also select the lines, right click, then shift right / shift left

It seems source formatting is still not available in PyDev.
For one off instances I found this web app does the job nicely.
http://pythoniter.appspot.com/

Like earlier said python requires to indent your code, so for other things like: space between variables passed as arguments to methods, etc., one can use ctrl+shift+f to format the code. This what is used for java, I tried for pydev and does some formatting.

In Python what's the best way to emulate Perl's __END__?

Am I correct in thinking that that Python doesn't have a direct equivalent for Perl's __END__?
print "Perl...\n";
__END__
End of code. I can put anything I want here.
One thought that occurred to me was to use a triple-quoted string. Is there a better way to achieve this in Python?
print "Python..."
"""
End of code. I can put anything I want here.
"""

The __END__ block in perl dates from a time when programmers had to work with data from the outside world and liked to keep examples of it in the program itself.
Hard to imagine I know.
It was useful for example if you had a moving target like a hardware log file with mutating messages due to firmware updates where you wanted to compare old and new versions of the line or keep notes not strictly related to the programs operations ("Code seems slow on day x of month every month") or as mentioned above a reference set of data to run the program against. Telcos are an example of an industry where this was a frequent requirement.
Lastly Python's cult like restrictiveness seems to have a real and tiresome effect on the mindset of its advocates, if your only response to a question is "Why would you want to that when you could do X?" when X is not as useful please keep quiet++.

The triple-quote form you suggested will still create a python string, whereas Perl's parser simply ignores anything after __END__. You can't write:
"""
I can put anything in here...
Anything!
"""
import os
os.system("rm -rf /")
Comments are more suitable in my opinion.
#__END__
#Whatever I write here will be ignored
#Woohoo !

What you're asking for does not exist.
Proof: http://www.mail-archive.com/python-list#python.org/msg156396.html
A simple solution is to escape any " as \" and do a normal multi line string -- see official docs: http://docs.python.org/tutorial/introduction.html#strings
( Also, atexit doesn't work: http://www.mail-archive.com/python-list#python.org/msg156364.html )

Hm, what about sys.exit(0) ? (assuming you do import sys above it, of course)
As to why it would useful, sometimes I sit down to do a substantial rewrite of something and want to mark my "good up to this point" place.
By using sys.exit(0) in a temporary manner, I know nothing below that point will get executed, therefore if there's a problem (e.g., server error) I know it had to be above that point.
I like it slightly better than commenting out the rest of the file, just because there are more chances to make a mistake and uncomment something (stray key press at beginning of line), and also because it seems better to insert 1 line (which will later be removed), than to modify X-many lines which will then have to be un-modified later.
But yeah, this is splitting hairs; commenting works great too... assuming your editor supports easily commenting out a region, of course; if not, sys.exit(0) all the way!

I use __END__ all the time for multiples of the reasons given. I've been doing it for so long now that I put it (usually preceded by an exit('0');), along with BEGIN {} / END{} routines, in by force-of-habit. It is a shame that Python doesn't have an equivalent, but I just comment-out the lines at the bottom: extraneous, but that's about what you get with one way to rule them all languages.

Python does not have a direct equivalent to this.
Why do you want it? It doesn't sound like a really great thing to have when there are more consistent ways like putting the text at the end as comments (that's how we include arbitrary text in Python source files. Triple quoted strings are for making multi-line strings, not for non-code-related text.)
Your editor should be able to make using many lines of comments easy for you.