Only download if file doesn't exist in current directory

[twhitehead]

This changes the URL download code to first check if the file exists in the current directory and uses that if it does before going ahead and download it.

I think this is a good thing as it allows us to package the installer alongside the packages it downloads on a USB key and have people use it at workshops without a working network.

Note that I have only tested these changes by directly running the installer script on my Linux machine. I don't expect a Windows machine will be any different, but I don't have easy access to test it.

[wking]

On Fri, Jan 08, 2016 at 01:09:04PM -0800, Tyson Whitehead wrote:

I think this is a good thing as it allows us to package the installer alongside the packages it downloads on a USB key and have people use it at workshops without a working network.

Yeah, sounds good to me.

Note that I have only tested these changes by directly running the installer script on my Linux machine. I don't expect a Windows machine will be any different, but I don't have easy access to test it.

My concern here would be that os.path.basename would be splitting on backslashes on Windows. I expect we want:

url.split('/')[-1]

And to avoid a race between isfile and open, I'd just try/catch:

try: r = open(url.split('/')[-1]) except (IOError, FileNotFoundError): r = _urlopen(url)

The two exceptions allow us to work with either Python 2 or 3 (after the great exception reorganization [1,2,3]).

[twhitehead]

Those both sound like good points to me. I'll make the corrections

[twhitehead]

Specifying the Python 2 and 3 exceptions doesn't work under Python 2. Here is the backtrace

Traceback (most recent call last): File "./swc-windows-installer.py", line 329, in main() File "./swc-windows-installer.py", line 296, in main install_nano(install_directory=nano_dir) File "./swc-windows-installer.py", line 176, in install_nano install_directory=install_directory) File "./swc-windows-installer.py", line 144, in zip_install zip_bytes = download(url=url, sha1=sha1) File "./swc-windows-installer.py", line 74, in download except (IOError,FileNotFoundError): NameError: global name 'FileNotFoundError' is not defined

One solution that occurs to me would be to take advantage of your existing Python 2 vs 3 branch to make sure FileNotFoundError is always defined and then just catch it.

try:  # Python 3
    from urllib.request import urlopen as _urlopen
except ImportError:  # Python 2
    from urllib2 import urlopen as _urlopen
    FileNotFoundError = IOError

[wking]

On Fri, Jan 08, 2016 at 05:31:10PM -0800, Tyson Whitehead wrote:

One solution that occurs to me would be to take advantage of your existing Python 2 vs 3 branch to make sure FileNotFoundError is always defined and then just catch it.

try:  # Python 3
    from urllib.request import urlopen as _urlopen
except ImportError:  # Python 2
    from urllib2 import urlopen as _urlopen
    FileNotFoundError = IOError

Ah, that works. I'd prefer a separate:

if sys.version_info.major < 3: FileNotFoundError = IOError

after the imports though, to avoid crowding the urlopen section.

[embray]

LGTM modulo the change @wking suggested. I can finish this up if you don't have the chance @twhitehead