How can I automatically wrap long python strings so that they print correctly?
Specifically, I am trying to add help strings with optparse which I want to be able to modify easily.
I have found several methods of dealing with long strings, none of which allow me to refill after making changes using M-q in emacs or similar:
p.add_option('-a', help = "this is my\
long help text")
forces newlines in the result and doesn't allow refilling
p.add_option('-a', help = "this is my "
"long help text")
formats correctly but doesn't allow refilling
p.add_option('-a', help = '''
this is my
long help text
''')
formats incorrectly but does allow refilling
p.add_option('-a', help = dedent('''
this is my
long help text
'''))
is the best option I've found, formats almost correctly and allows refilling but results in an additional space at the beginning of the string.
The docs use dedent so it seems reasonable, especially if it works. If you want to drop the leading space you could:
help = dedent('''
this is my
long help text
''')[1:]
although
dedent(…).lstrip()
might be more obvious.
Use argparse instead of optparse, if you are using Python >= 2.7. It does dedent for you. You can just do:
parser.add_argument('--argument', '-a', help='''
this is my
long help text
''')
Even if you are using Python < 2.7, you can install argparse from pypi.
Note that there is a way to suppress this auto-dedent behavior. The link given by #msw is actually the section about it.
I'm not 100% sure what refilling is, but here's what I typically use:
p.add_option('-a', help = ("this is my "
"long help text"))
(note the additional parenthesis). Emacs lines up the next line with the previous open parenthesis for me.
Related
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.
In TextMate 1.5.10 r1623, you get little arrows that allow you to fold method blocks:
Unfortunately, if you have a multi-lined Python comment, it doesn't recognize it, so you can't fold it:
def foo():
"""
How do
I fold
these comments?
"""
print "bar"
TextMate has this on their site on how to customize folding: http://manual.macromates.com/en/navigation_overview#customizing_foldings
...but I'm not skilled in regex enough to do anything about it. TextMate uses the Oniguruma regex API, and I'm using the default Python.tmbundle updated to the newest version via GetBundles.
Does anyone have an idea of how to do this? Thanks in advance for your help! :)
Adding the default foldingStartMarker and foldingStopMarker regex values for Python.tmbundle under the Python Language in Bundle Editor:
foldingStartMarker = '^\s*(def|class)\s+([.a-zA-Z0-9_ <]+)\s*(\((.*)\))?\s*:|\{\s*$|\(\s*$|\[\s*$|^\s*"""(?=.)(?!.*""")';
foldingStopMarker = '^\s*$|^\s*\}|^\s*\]|^\s*\)|^\s*"""\s*$';
It appears that multi-line comment folding does work in TextMate, but your must line up your quotes exactly like so:
""" Some sort of multi
line comment, which needs quotes
in just the right places to work. """
That seems to do it:
According to this Textmate Mailing list thread, if you follow it to the end, proper code folding for Python is not supported. Basically, regular expressions as implemented in the foldingStartMarker and foldingStopMarker do not allow for captures, thus the amount of spacing at the beginning of the "end fold" cannot be matched to the "begin fold".
The issue is not finally and officially addressed by Textmate's creator, Allan Odgaard; however since the thread is from 2005, I assume it is a dead issue, and not one that will be supported.
Is there some way to just get the next token from a file in Python, as for example the Scanner class does in Java?
File file = new File("something");
Scanner myinput = new Scanner(file);
double a = myinput.nextDouble();
String s = myinput.next();
I'd like to ignore whitespaces, tabs, newlines and just get the next int/float/word from the file. I know I could read the lines and build something like Scanner myself, but I'd like to know if there isn't already something that I could use.
I've searched around but could only find line-oriented methods.
Thank you!
Check out the shlex-module in the standard library: http://docs.python.org/library/shlex.html
import shlex
import StringIO # use in place of files
list(shlex.shlex(StringIO.StringIO('Some tokens. 123, 45.67 "A string with whitespace"')))
It does not handle floats the way you seem to want. Maybe you can extend or modify it.
I don't think there is really something around that sophisticated.
But you can take a look at the following options
use re.split(pattern, string) and get what you want by providing regex's
There is somewhere a Scanner class in the re module (but I don't think they developed it further)
You could also consider using tokenize + StringIO
Or as you yourself mentioned: Build one yourself, donate it do community and get famous ;)
Probably you can take a look at PLY
if your file is *.ini alike text files, you could use ConfigParser module
There is few examples out there.
http://docs.python.org/library/configparser.html
and pyparsing will do that for other purpose, I think.
I havn't use pyparsing before, so I have no clue right now.
http://pyparsing.wikispaces.com/
I have a script that uses the cmd Python module. The cmd module uses a triple quoted multiline string as it's help text. Something like this
def x(self, strags = None):
"""class
help text here
and some more help text here"""
When running the script, the command 'help x' will print the string. It will, however, print the newlines in front of the last two lines as well. I can overcome this by not indenting these lines, but that'll make my code ugl{y,ier}.
How to overcome this indenting problem? How do the pro Python coders handle this?
Personally I try to follow PEP 8 which refers the reader to PEP 257 for Docstring Conventions. It has an entire section on multi-line docstrings.
I'd handle it by having consistent indents, like this:
def x(self, strags = None):
"""
class
help text here
and some more help text here
"""
Sure, it takes two lines more, but it also injects clarity (in my opinion) by making the doc comment stand out quite well.
I am a totally blind programmer who would like to learn Python. Unfortunately the fact that code blocks are represented with different levels of indentation is a major stumbling block. I was wondering if there were any tools available that would allow me to write code using braces or some other code block delimiter and then convert that format into a properly indented representation that the Python interpreter could use?
There's a solution to your problem that is distributed with python itself. pindent.py, it's located in the Tools\Scripts directory in a windows install (my path to it is C:\Python25\Tools\Scripts), it looks like you'd have to grab it from svn.python.org if you are running on Linux or OSX.
It adds comments when blocks are closed, or can properly indent code if comments are put in. Here's an example of the code outputted by pindent with the command:
pindent.py -c myfile.py
def foobar(a, b):
if a == b:
a = a+1
elif a < b:
b = b-1
if b > a: a = a-1
# end if
else:
print 'oops!'
# end if
# end def foobar
Where the original myfile.py was:
def foobar(a, b):
if a == b:
a = a+1
elif a < b:
b = b-1
if b > a: a = a-1
else:
print 'oops!'
You can also use pindent.py -r to insert the correct indentation based on comments (read the header of pindent.py for details), this should allow you to code in python without worrying about indentation.
For example, running pindent.py -r myfile.py will convert the following code in myfile.py into the same properly indented (and also commented) code as produced by the pindent.py -c example above:
def foobar(a, b):
if a == b:
a = a+1
elif a < b:
b = b-1
if b > a: a = a-1
# end if
else:
print 'oops!'
# end if
# end def foobar
I'd be interested to learn what solution you end up using, if you require any further assistance, please comment on this post and I'll try to help.
I personally doubt that there currently is at the moment, as a lot of the Python afficionados love the fact that Python is this way, whitespace delimited.
I've never actually thought about that as an accessibility issue however. Maybe it's something to put forward as a bug report to Python?
I'd assume that you use a screen reader here however for the output? So the tabs would seem "invisible" to you? With a Braille output, it might be easier to read, but I can understand exactly how confusing this could be.
In fact, this is very interesting to me. I wish that I knew enough to be able to write an app that will do this for you.
I think it's definately something that I'll put in a bug report for, unless you've already done so yourself, or want to.
Edit: Also, as noted by John Millikin There is also PyBraces Which might be a viable solution to you, and may be possible to be hacked together dependant on your coding skills to be exactly what you need (and I hope that if that's the case, you release it out for others like yourself to use)
Edit 2: I've just reported this to the python bug tracker
Although I am not blind, I have heard good things about Emacspeak. They've had a Python mode since their 8.0 release in 1998 (they seem to be up to release 28.0!). Definitely worth checking out.
You should be able to configure your editor to speak the tabs and spaces -- I know it's possible to display whitespace in most editors, so there must be an accessibility option somewhere to speak them.
Failing that, there is pybraces, which was written as a practical joke but might actually be useful to you with a bit of work.
If you're on Windows, I strongly recommend you take a look at EdSharp from:
http://empowermentzone.com/EdSharp.htm
It supports all of the leading Windows screenreaders, it can be configured to speak the indentation levels of code, or it has a built in utility called PyBrace that can convert to and from braces syntax if you want to do that instead, and it supports all kinds of other features programmers have come to expect in our text editors. I've been using it for years, for everything from PHP to JavaScript to HTML to Python, and I love it.
All of these "no you can't" types of answers are really annoying. Of course you can.
It's a hack, but you can do it.
http://timhatch.com/projects/pybraces/
uses a custom encoding to convert braces to indented blocks before handing it off to the interpreter.
As an aside, and as someone new to python - I don't accept the reasoning behind not even allowing braces/generic block delimiters ... apart from that being the preference of the python devs. Braces at least won't get eaten accidentally if you're doing some automatic processing of your code or working in an editor that doesn't understand that white space is important. If you're generating code automatically, it's handy to not have to keep track of indent levels. If you want to use python to do a perl-esque one-liner, you're automatically crippled. If nothing else, just as a safeguard. What if your 1000 line python program gets all of its tabs eaten? You're going to go line-by-line and figure out where the indenting should be?
Asking about it will invariably get a tongue-in-cheek response like "just do 'from __ future __ import braces'", "configure your IDE correctly", "it's better anyway so get used to it" ...
I see their point, but hey, if i wanted to, i could put a semicolon after every single line. So I don't understand why everyone is so adamant about the braces thing. If you need your language to force you to indent properly, you're not doing it right in the first place.
Just my 2c - I'm going to use braces anyway.
I appreciate your problem, but think you are specifying the implementation instead of the problem you need solved. Instead of converting to braces, how about working on a way for your screen reader to tell you the indentation level?
For example, some people have worked on vim syntax coloring to represent python indentation levels. Perhaps a modified syntax coloring could produce something your screen reader would read?
Searching an accessible Python IDE, found this and decided to answer.
Under Windows with JAWS:
Go to Settings Center by pressing JawsKey+6 (on the number row above the letters) in your favorite text editor. If JAWS prompts to create a new configuration file, agree.
In the search field, type "indent"
There will be only one result: "Say indent characters". Turn this on.
Enjoy!
The only thing that is frustrating for us is that we can't enjoy code examples on websites (since indent speaking in browsers is not too comfortable — it generates superfluous speech).
Happy coding from another Python beginner).
I use eclipse with the pydev extensions since it's an IDE I have a lot of experience with. I also appreciate the smart indentation it offers for coding if statements, loops, etc. I have configured the pindent.py script as an external tool that I can run on the currently focused python module which makes my life easier so I can see what is closed where with out having to constantly check indentation.
There are various answers explaining how to do this. But I would recommend not taking this route. While you could use a script to do the conversion, it would make it hard to work on a team project.
My recommendation would be to configure your screen reader to announce the tabs. This isn't as annoying as it sounds, since it would only say "indent 5" rather than "tab tab tab tab tab". Furthermore, the indentation would only be read whenever it changed, so you could go through an entire block of code without hearing the indentation level. In this way hearing the indentation is no more verbose than hearing the braces.
As I don't know which operating system or screen reader you use I unfortunately can't give the exact steps for achieving this.
Edsger Dijkstra used if ~ fi and do ~ od in his "Guarded Command Language", these appear to originate from the Algol68. There were also some example python guarded blocks used in RosettaCode.org.
fi = od = yrt = end = lambda object: None;
class MyClass(object):
def myfunction(self, arg1, arg2):
for i in range(arg1) :# do
if i > 5 :# then
print i
fi
od # or end(i) #
end(myfunction)
end(MyClass)
Whitespace mangled python code can be unambiguously unmangled and reindented if one uses
guarded blocks if/fi, do/od & try/yrt together with semicolons ";" to separate statements. Excellent for unambiguous magazine listings or cut/pasting from web pages.
It should be easy enough to write a short python program to insert/remove the guard blocks and semicolons.