Browser selection

[ivanov]

Someone in the Astronomy 250: Python for Scientific Computing class asked how one can specify which browser is used for the notebook interface. I found that this was undocumented, and added a description of how one can do it using environment variable BROWSER, since that's what python standard libarary's webbrowser module looks at to override the default. This is the first commit in the PR

In talking with @stefanv about it, we decided it's be more pythonic to be able to specifically specify --browser=foo, since the environment solution makes a change for any other code that uses the webbrowser standard library module and feels awkward if you want to change it to have to change it at the beginning of every command. That's the second commit, but it does not preclude the first (i.e. $BROWSER is still respected when --browser is not used)

[minrk]

Why would we ever launch with anything other than the user's default? I can't think of a single application that allows opening a url in a webbrowser that lets you choose one other than the system default.

[stefanv]

My default browser is Firefox, but I typically want to run the notebooks in Chrome. I don't think this is an uncommon situation at all.

[ivanov]

I can't think of a single application that allows opening a url in a webbrowser that lets you choose one other than the system default.

IPython's Notebook very different from any other application that opens URLs - the URLs those other applications open are typically viewable in any web browser - whereas the Notebook is currently usable only on the more recent version of Firefox and Chrome.

So I might have uzbl or opera or vimprobable or w3m or surf etc as my system default browser - where I want all of my urls to open inside of - given the current features required for the nice user experience of the ipython notebook, I ought to be able to configure a separate IPython specific default.

[takluyver]

I think this is reasonable, since the default browser may not be up to running the notebook, and the extra code complexity seems minimal.

Just to check one thing: I think there was a command-line flag like --no-browser to prevent launching a browser. I assume this doesn't interfere with that?

(Of course, the option to suppress a browser could work like --browser=no, but I think the --no-browser flag is still clearer)

[stefanv]

Hehe, I love the idea of browser=no, but I would hate to shout at my IPython like that :)

[minrk]

Okay, fair points all, and this seems like a reasonable solution for a real use case I didn't expect to exist. From my perspective: I disabled the browser launch, because I find it super annoying.

[minrk]

Isn't a simpler if self.browser: test more logical here?

[ivanov]

fair point, i knew it looked too ugly but forgot about this cleaner syntax.

[ivanov]

Just to check one thing: I think there was a command-line flag like --no-browser to prevent launching a browser. I assume this doesn't interfere with that?

no it doesn't, --no-browser still works as it always did - although maybe I should change it such that using --browser=foo automatically overrides NotebookApp.open_browser=False, and then document it as much in the --browser doc string (i.e. in --browser description say "using this option overrides NotebookApp.open_browser=False" - what do ya'll think?

[takluyver]

Yes, I think that makes sense - not so much for the --no-browser flag, but if someone sets ..open_browser=False in config, they might want to override it with --browser=firefox.

[minrk]

maybe I should change it such that using --browser=foo automatically overrides NotebookApp.open_browser=False

You will want to be a bit careful with this, because you don't want config-file values to end up overriding those set at the command-line.

[ivanov]

yeah, actually, after more examination, I think I want to leave this as is - I don't see a way of disambiguate --no-browser from NotebookApp.open_browser=False set in the profile config.

So this is ready to merge as far as I'm concerned.