read_fwf with urlopen test GH#26376

[liang3zy22]

• closes pd.read_fwf fails with file pointer to url #26376 (Replace xxxx with the GitHub issue number)
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.

To avoid download file, I just compare the columns.

[mroeschke]

Can you use this as a context manager?

[liang3zy22]

If I added check_before_test=True, in the tm.network decorator then run the test case. Following error will be reported:

test_read_fwf.py::test_url_urlopen FAILED
pandas/tests/io/parser/test_read_fwf.py:1015 (test_url_urlopen)
args = (), kwargs = {}

    @wraps(t)
    def wrapper(*args, **kwargs):
        if (
            check_before_test
            and not raise_on_error
>           and not can_connect(url, error_classes)
        ):

../../../_testing/_io.py:222: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../../_testing/_io.py:274: in can_connect
    if response.status != 200:
/Users/username/mambaforge/envs/pandas-dev/lib/python3.8/tempfile.py:468: in __getattr__
    a = getattr(file, name)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <addclosehook at 5811361200 whose fp = <_io.BufferedReader name=-1>>
name = 'status'

    def __getattr__(self, name):
        # Attribute lookups are delegated to the underlying file
        # and cached for non-numeric results
        # (i.e. methods are cached, closed and friends are not)
        file = self.__dict__['file']
>       a = getattr(file, name)
E       AttributeError: '_io.BufferedReader' object has no attribute 'status'

/Users/username/mambaforge/envs/pandas-dev/lib/python3.8/tempfile.py:468: AttributeError

It seems like a bug in the tm codes?

[mroeschke]

Can you put this outside the context manager?

[mroeschke]

Suggested change

	url=("ftp://ftp.ncdc.noaa.gov/pub/data/igra/igra2-station-list.txt"),
	url="ftp://ftp.ncdc.noaa.gov/pub/data/igra/igra2-station-list.txt",

[mroeschke]

It seems like a bug in the tm codes?

Could you diagnose how to check if ftp urls are connectable?

[liang3zy22]

I done some diagnosis. url open with ftp will return a urllib.response.addinfourl instance. There is a status method of addinfourl, but from python 3.9 only. And I have tried using python 3.10, the status only return None.

It seems that if the ftp url can be open, then it is also connectable. So I added codes in can_connect to only check http/https url status.

[mroeschke]

Thanks for the test and nice investigation @liang3zy22