"""
Functions to download, verify, and update a sample dataset.
"""
import os
import sys
from pathlib import Path
import shutil
import tempfile
from warnings import warn
import requests
from .utils import file_hash, check_version
# PermissionError was introduced in Python 3.3. This can be deleted when dropping 2.7
if sys.version_info[0] < 3:
PermissionError = OSError # pylint: disable=redefined-builtin,invalid-name
[docs]def create(path, base_url, version, version_dev, env=None, registry=None):
"""
Create a new :class:`~pooch.Pooch` with sensible defaults to fetch data files.
The Pooch will be versioned, meaning that the local storage folder and the base URL
depend on the projection version. This is necessary if your users have multiple
versions of your library installed (using virtual environments) and you updated the
data files between versions. Otherwise, every time a user switches environments
would trigger a re-download of the data.
The version string will be appended to the local storage path (for example,
``~/.mypooch/cache/v0.1``) and inserted into the base URL (for example,
``https://github.com/fatiando/pooch/raw/v0.1/data``). If the version string
contains ``+XX.XXXXX``, it will be interpreted as a development version.
Parameters
----------
path : str, PathLike, list or tuple
The path to the local data storage folder. If this is a list or tuple, we'll
join the parts with the appropriate separator. The *version* will be appended to
the end of this path. Use :func:`pooch.os_cache` for a sensible default.
base_url : str
Base URL for the remote data source. All requests will be made relative to this
URL. The string should have a ``{version}`` formatting mark in it. We will call
``.format(version=version)`` on this string. If the URL is a directory path, it
must end in a ``'/'`` because we will not include it.
version : str
The version string for your project. Should be PEP440 compatible.
version_dev : str
The name used for the development version of a project. If your data is hosted
on Github (and *base_url* is a Github raw link), then ``"master"`` is a good
choice.
env : str
An environment variable that can be used to overwrite *path*. This allows users
to control where they want the data to be stored. We'll append *version* to the
end of this value as well.
registry : dict
A record of the files that are managed by this Pooch. Keys should be the file
names and the values should be their SHA256 hashes. Only files in the registry
can be fetched from the local storage. Files in subdirectories of *path* **must
use Unix-style separators** (``'/'``) even on Windows.
Returns
-------
pooch : :class:`~pooch.Pooch`
The :class:`~pooch.Pooch` initialized with the given arguments.
Examples
--------
Create a :class:`~pooch.Pooch` for a release (v0.1):
>>> pup = create(path="myproject",
... base_url="http://some.link.com/{version}/",
... version="v0.1",
... version_dev="master",
... registry={"data.txt": "9081wo2eb2gc0u..."})
>>> print(pup.path.parts) # The path is a pathlib.Path
('myproject', 'v0.1')
>>> print(pup.base_url)
http://some.link.com/v0.1/
>>> print(pup.registry)
{'data.txt': '9081wo2eb2gc0u...'}
If this is a development version (12 commits ahead of v0.1):
>>> pup = create(path="myproject",
... base_url="http://some.link.com/{version}/",
... version="v0.1+12.do9iwd",
... version_dev="master")
>>> print(pup.path.parts)
('myproject', 'master')
>>> print(pup.base_url)
http://some.link.com/master/
To place the storage folder at a subdirectory, pass in a list and we'll join the
path for you using the appropriate separator for your operating system:
>>> pup = create(path=["myproject", "cache", "data"],
... base_url="http://some.link.com/{version}/",
... version="v0.1",
... version_dev="master")
>>> print(pup.path.parts)
('myproject', 'cache', 'data', 'v0.1')
The user can overwrite the storage path by setting an environment variable:
>>> # The variable is not set so we'll use *path*
>>> pup = create(path=["myproject", "not_from_env"],
... base_url="http://some.link.com/{version}/",
... version="v0.1",
... version_dev="master",
... env="MYPROJECT_DATA_DIR")
>>> print(pup.path.parts)
('myproject', 'not_from_env', 'v0.1')
>>> # Set the environment variable and try again
>>> import os
>>> os.environ["MYPROJECT_DATA_DIR"] = os.path.join("myproject", "from_env")
>>> pup = create(path=["myproject", "not_from_env"],
... base_url="http://some.link.com/{version}/",
... version="v0.1",
... version_dev="master",
... env="MYPROJECT_DATA_DIR")
>>> print(pup.path.parts)
('myproject', 'from_env', 'v0.1')
"""
version = check_version(version, fallback=version_dev)
if isinstance(path, (list, tuple)):
path = os.path.join(*path)
if env is not None and env in os.environ and os.environ[env]:
path = os.environ[env]
versioned_path = os.path.join(os.path.expanduser(str(path)), version)
# Check that the data directory is writable
try:
if not os.path.exists(versioned_path):
os.makedirs(versioned_path)
else:
tempfile.NamedTemporaryFile(dir=versioned_path)
except PermissionError:
message = (
"Cannot write to data cache '{}'. "
"Will not be able to download remote data files. ".format(versioned_path)
)
if env is not None:
message = (
message
+ "Use environment variable '{}' to specify another directory.".format(
env
)
)
warn(message)
if registry is None:
registry = dict()
pup = Pooch(
path=Path(versioned_path),
base_url=base_url.format(version=version),
registry=registry,
)
return pup
[docs]class Pooch:
"""
Manager for a local data storage that can fetch from a remote source.
Parameters
----------
path : str
The path to the local data storage folder. The path must exist in the file
system.
base_url : str
Base URL for the remote data source. All requests will be made relative to this
URL.
registry : dict
A record of the files that are managed by this good boy. Keys should be the file
names and the values should be their SHA256 hashes. Only files in the registry
can be fetched from the local storage. Files in subdirectories of *path* **must
use Unix-style separators** (``'/'``) even on Windows.
"""
def __init__(self, path, base_url, registry):
self.path = path
self.base_url = base_url
self.registry = dict(registry)
@property
def abspath(self):
"Absolute path to the local storage"
return Path(os.path.abspath(os.path.expanduser(str(self.path))))
[docs] def fetch(self, fname):
"""
Get the absolute path to a file in the local storage.
If it's not in the local storage, it will be downloaded. If the hash of the file
in local storage doesn't match the one in the registry, will download a new copy
of the file. This is considered a sign that the file was updated in the remote
storage. If the hash of the downloaded file still doesn't match the one in the
registry, will raise an exception to warn of possible file corruption.
Parameters
----------
fname : str
The file name (relative to the *base_url* of the remote data storage) to
fetch from the local storage.
Returns
-------
full_path : str
The absolute path (including the file name) of the file in the local
storage.
"""
if fname not in self.registry:
raise ValueError("File '{}' is not in the registry.".format(fname))
# Create the local data directory if it doesn't already exist
if not self.abspath.exists():
os.makedirs(str(self.abspath))
full_path = self.abspath / fname
in_storage = full_path.exists()
if not in_storage:
action = "Downloading"
elif in_storage and file_hash(str(full_path)) != self.registry[fname]:
action = "Updating"
else:
action = "Nothing"
if action in ("Updating", "Downloading"):
warn(
"{} data file '{}' from remote data store '{}' to '{}'.".format(
action, fname, self.base_url, str(self.path)
)
)
self._download_file(fname)
return str(full_path)
def _download_file(self, fname):
"""
Download a file from the remote data storage to the local storage.
Parameters
----------
fname : str
The file name (relative to the *base_url* of the remote data storage) to
fetch from the local storage.
Raises
------
ValueError
If the hash of the downloaded file doesn't match the hash in the registry.
"""
destination = self.abspath / fname
source = "".join([self.base_url, fname])
# Stream the file to a temporary so that we can safely check its hash before
# overwriting the original
with tempfile.NamedTemporaryFile(delete=False) as fout:
response = requests.get(source, stream=True)
response.raise_for_status()
for chunk in response.iter_content(chunk_size=1024):
if chunk:
fout.write(chunk)
tmphash = file_hash(fout.name)
if tmphash != self.registry[fname]:
raise ValueError(
"Hash of downloaded file '{}' doesn't match the entry in the registry:"
" Expected '{}' and got '{}'.".format(
fout.name, self.registry[fname], tmphash
)
)
# Make sure the parent directory exists in case the file is in a subdirectory.
# Otherwise, move will cause an error.
if not os.path.exists(str(destination.parent)):
os.makedirs(str(destination.parent))
shutil.move(fout.name, str(destination))
[docs] def load_registry(self, fname):
"""
Load entries form a file and add them to the registry.
Use this if you are managing many files.
Each line of the file should have file name and its SHA256 hash separate by a
space. Only one file per line is allowed.
Parameters
----------
fname : str
File name and path to the registry file.
"""
with open(fname) as fin:
for linenum, line in enumerate(fin):
elements = line.strip().split()
if len(elements) != 2:
raise ValueError(
"Expected 2 elements in line {} but got {}.".format(
linenum, len(elements)
)
)
file_name, file_sha256 = elements
self.registry[file_name] = file_sha256