issue_comments

Awesome, thanks so much @laliberte!

I also like the idea of passing PydapDataStore objects that include the session object. Delving deeper into the pydap authentication, I found that there are already several different setup_session functions available to create the session object, corresponding to different authentication procedures (pydap.cas.get_cookies.setup_session, pydap.cas.urs.setup_session, pydap.cas.esgf.setup_session) as well as additional arguments to setup_session beyond username and password. Best to deal with all this separately with pydap rather than trying to embed it within xarray.

I'm still having problems trying to get xarray.open_dataset to work with pydap. Using the latest commit on pydap/master (in which https://github.com/pydap/pydap/pull/48 is merged) I'm now getting a new error: AttributeError: '<class 'pydap.model.BaseType'>' object has no attribute 'encode'. When I have some time, I'll look into it further and try to see what else is needed to restore compatibility.

Thanks, @rabernat! I'd be happy to try implementing this in the project. I'm a newbie when it comes to contributing to big projects like this (so far I've just used Github for my own little projects) so I might have some naive questions as I figure out how things work.

The two options you mentioned for passing username and password info to open_dataset both sound good to me. I don't have any strong preference between them. How do I get other opinions on which approach to use? Should I start a new issue thread?

Also, I realized that there is another hiccup along the way. When I try to specify engine='pydap' in open_dataset, I get the same error message as mentioned in #1174, that the object has no attribute iteritems. When I wrote the first post in this thread, back in October, I was able to use engine='pydap' without any problems. This seems to be related to recent upstream changes in Pydap: https://github.com/pydap/pydap/issues/43 and I presume might require more substantial changes either in Xarray or Pydap so that they can work together again. Any thoughts on how to handle this?

I've finally found something useful online and am able to use Pydap to open these files -- hoping someone can help me find a way to integrate this into an xarray.open_dataset() function call and then I will be a very happy camper!

Turns out much of the info posted by NASA online is out of date and based on a different implementation of Pydap than what is actually being used currently (argh). Here is something that actually works, from http://www.pydap.org/en/latest/client.html#urs-nasa-earthdata: ``` from pydap.client import open_url from pydap.cas.urs import setup_session

url = 'https://goldsmr4.gesdisc.eosdis.nasa.gov/opendap/MERRA2/M2T1NXSLV.5.12.4/2016/06/MERRA2_400.tavg1_2d_slv_Nx.20160601.nc4'

session = setup_session(username, password) dataset = open_url(url, session=session) ``` where I've assigned the username and password variables with the appropriate values in another function.

I've tested this and it is working, but I would prefer to do things within Xarray since all my code is already using it. Just for fun, I tried ds = xarray.open_dataset(url, engine='pydap', session=session), to see if the extra keyword would be magically sent to the pydap engine, but got an error message. Is there a way to incorporate this functionality into xarray.open_dataset? Thank you so much for any assistance!

@j08lue no, not yet. I've been in touch with the folks at NASA who run the server, but their suggestions didn't work for me and I haven't had time to keep troubleshooting. I will need to sort out this issue in the next couple of months to get some data that I need, so if/when I ever resolve it, I'll post the solution here.

Ah, I see. Thanks for the suggestion. Using Pydap I'm able to see all the variables and their metadata, so I thought it was working, but when I try to actually access the data values, I get the same error message as from Xarray. The issue must be something unrelated to Xarray -- I'll keep investigating. Thanks for your help!

Thanks very much for your reply! I still get an error from xarray when I use the engine='pydap' option. Here's a minimum (almost) working example (almost because you need an account with the server so you can substitute your username/password into the url string):

``` import xarray from pydap.client import open_url

url = 'http://<username>:<password>@goldsmr5.sci.gsfc.nasa.gov/opendap/MERRA2/M2I3NPASM.5.12.4/1986/01/MERRA2_100.inst3_3d_asm_Np.19860101.nc4'

ds1 = open_url(url) # Works but data isn't in xarray format ds2 = xarray.open_dataset(url, engine='pydap') # Error message, see attached ```

I've attached the error message here -- error_msg.txt I don't know enough about the inner workings of xarray to trace through it. Please let me know if any of this means anything to you and has a reasonably easy fix or workaround. Thank you!