add error for invalid data locations

elephant/datasets.py

@@ -2,6 +2,7 @@
 import os
 import ssl
 import tempfile
+from urllib.parse import urlparse
 import warnings
 from os import environ, getenv
 from pathlib import Path
@@ -75,72 +76,76 @@ def download(url, filepath=None, checksum=None, verbose=True):
 def download_datasets(repo_path, filepath=None, checksum=None,
                       verbose=True):
     r"""
-        This function can be used to download files from elephant-data using
-        only the path relative to the root of the elephant-data repository.
-        The default URL used, points to elephants corresponding release of
-        elephant-data.
-        Different versions of the elephant package may require different
-        versions of elephant-data.
-        e.g. the following URLs:
-        -  https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/0.0.1
-           points to release v0.0.1.
-        -  https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/master
-           always points to the latest state of elephant-data.
-        -  https://datasets.python-elephant.org/
-           points to the root of elephant data
-
-        To change this URL, use the environment variable `ELEPHANT_DATA_LOCATION`.
-        When using data, which is not yet contained in the master branch or a
-        release of elephant data, e.g. during development, this variable can
-        be used to change the default URL.
-        For example to use data on branch `multitaper`, change the
-        `ELEPHANT_DATA_LOCATION` to
-        https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/multitaper.
-        For a complete example, see Examples section.
+    This function can be used to download files from elephant-data using
+    only the path relative to the root of the elephant-data repository.
+    The default URL used, points to elephants corresponding release of
+    elephant-data.
+    Different versions of the elephant package may require different
+    versions of elephant-data.
+    e.g. the following URLs:
+    -  https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/0.0.1
+       points to release v0.0.1.
+    -  https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/master
+       always points to the latest state of elephant-data.
+    -  https://datasets.python-elephant.org/
+       points to the root of elephant data
+
+    To change this URL, use the environment variable `ELEPHANT_DATA_LOCATION`.
+    When using data, which is not yet contained in the master branch or a
+    release of elephant data, e.g. during development, this variable can
+    be used to change the default URL.
+    For example to use data on branch `multitaper`, change the
+    `ELEPHANT_DATA_LOCATION` to
+    https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/multitaper.
+    For a complete example, see Examples section.
         
-        To use a local copy of elephant-data, use the environment variable
-        `ELEPHANT_DATA_LOCATION`, e.g. set to /home/user/elephant-data.
+    To use a local copy of elephant-data, use the environment variable
+    `ELEPHANT_DATA_LOCATION`, e.g. set to /home/user/elephant-data.
         
-        Parameters
-        ----------
-        repo_path : str
-            String denoting the path relative to elephant-data repository root
-        filepath : str, optional
-            Path to temporary folder where the downloaded files will be stored
-        checksum : str, optional
-            Checksum to verify data integrity after download
-        verbose : bool, optional
-            Whether to disable the entire progressbar wrapper [].
-            If set to None, disable on non-TTY.
-            Default: True
-
-        Returns
-        -------
-        filepath : pathlib.Path
-            Path to downloaded files.
-
-
-        Notes
-        -----
-        The default URL always points to elephant-data. Please
-        do not change its value. For development purposes use the environment
-        variable 'ELEPHANT_DATA_LOCATION'.
-
-        Examples
-        --------
-        The following example downloads a file from elephant-data branch
-        'multitaper', by setting the environment variable to the branch URL:
-
-        >>> import os
-        >>> from elephant.datasets import download_datasets
-        >>> os.environ["ELEPHANT_DATA_LOCATION"] = "https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/multitaper" # noqa
-        >>> download_datasets("unittest/spectral/multitaper_psd/data/time_series.npy") # doctest: +SKIP
-        PosixPath('/tmp/elephant/time_series.npy')
-        """
+    Parameters
+    ----------
+    repo_path : str
+        String denoting the path relative to elephant-data repository root
+    filepath : str, optional
+        Path to temporary folder where the downloaded files will be stored
+    checksum : str, optional
+        Checksum to verify data integrity after download
+    verbose : bool, optional
+        Whether to disable the entire progressbar wrapper [].
+        If set to None, disable on non-TTY.
+        Default: True
+
+    Returns
+    -------
+    filepath : pathlib.Path
+        Path to downloaded files.
+
+
+    Notes
+    -----
+    The default URL always points to elephant-data. Please
+    do not change its value. For development purposes use the environment
+    variable 'ELEPHANT_DATA_LOCATION'.
+
+    Examples
+    --------
+    The following example downloads a file from elephant-data branch
+    'multitaper', by setting the environment variable to the branch URL:
+
+    >>> import os
+    >>> from elephant.datasets import download_datasets
+    >>> os.environ["ELEPHANT_DATA_LOCATION"] = "https://web.gin.g-node.org/NeuralEnsemble/elephant-data/raw/multitaper" # noqa
+    >>> download_datasets("unittest/spectral/multitaper_psd/data/time_series.npy") # doctest: +SKIP
+    PosixPath('/tmp/elephant/time_series.npy')
+    """
 
-    if 'ELEPHANT_DATA_LOCATION' in environ:  # user did set path or URL
-        if os.path.exists(getenv('ELEPHANT_DATA_LOCATION')):
-            return Path(f"{getenv('ELEPHANT_DATA_LOCATION')}/{repo_path}")
+    env_var = 'ELEPHANT_DATA_LOCATION'
+    if env_var in os.environ:  # user did set path or URL
+        if os.path.exists(getenv(env_var)):
+            return Path(f"{getenv(env_var)}/{repo_path}")
+        elif urlparse(getenv(env_var)).scheme not in ('http', 'https'):
+            raise ValueError(f"The environment variable {env_var} must be set to either an existing file system path "
+                             f"or a valid URL. Given value: '{getenv(env_var)}' is neither.")
 
     # this url redirects to the current location of elephant-data
     url_to_root = "https://datasets.python-elephant.org/"
@@ -149,7 +154,7 @@ def download_datasets(repo_path, filepath=None, checksum=None,
     # (version elephant is equal to version elephant-data)
     default_url = url_to_root + f"raw/v{_get_version()}"
 
-    if 'ELEPHANT_DATA_LOCATION' not in environ:  # user did not set URL
+    if env_var not in environ:  # user did not set URL
         # is 'version-URL' available? (not for elephant development version)
         try:
             urlopen(default_url+'/README.md')
@@ -177,7 +182,7 @@ def download_datasets(repo_path, filepath=None, checksum=None,
             warnings.warn(f"Data URL:{default_url}, error: {error}."
                           f"{error.reason}")
 
-    url = f"{getenv('ELEPHANT_DATA_LOCATION', default_url)}/{repo_path}"
+    url = f"{getenv(env_var, default_url)}/{repo_path}"
 
     return download(url, filepath, checksum, verbose)