Source code for ubelt.util_download

# -*- coding: utf-8 -*-
"""
Helpers for downloading data

The :func:`download` function access the network and requests the content at a
specific url using :mod:`urllib` or :mod:`urllib2`. You can either specify
where the data goes or download it to the default location in ubelt cache.
Either way this function returns the location of the downloaded data. You can
also specify the expected hash in order to check the validity of the data. By
default downloading is verbose.

The :func:`grabdata` function is almost identitcal to :func:`download`, but it
checks if the data already exists in the download location, and only downloads
if it needs to.

"""
from __future__ import (absolute_import, division, print_function,
                        unicode_literals)
from os.path import basename, join, exists
import six
import os


__all__ = ['download', 'grabdata']


[docs]def download(url, fpath=None, hash_prefix=None, hasher='sha512', chunksize=8192, verbose=1): """ Downloads a url to a file on disk. If unspecified the location and name of the file is chosen automatically. A hash_prefix can be specified to verify the integrity of the downloaded data. This function will download the data every time its called. For cached downloading see `grabdata`. Args: url (str): The url to download. fpath (PathLike | io.BytesIOtringIO): The path to download to. Defaults to basename of url and ubelt's application cache. If this is a io.BytesIO object then information is directly written to this object (note this prevents the use of temporary files). hash_prefix (None | str): If specified, download will retry / error if the file hash does not match this value. Defaults to None. hasher (str | Hasher): If hash_prefix is specified, this indicates the hashing algorithm to apply to the file. Defaults to sha512. chunksize (int, default=2 ** 13): Download chunksize. verbose (int, default=1): Verbosity level 0 or 1. Returns: PathLike: fpath - path to the downloaded file. Raises: URLError - if there is problem downloading the url RuntimeError - if the hash does not match the hash_prefix Notes: Based largely on code in pytorch [4]_ with modifications influenced by other resources [1]_ [2]_ [3]_. References: .. [1] http://blog.moleculea.com/2012/10/04/urlretrieve-progres-indicator/ .. [2] http://stackoverflow.com/questions/15644964/python-progress-bar-and-downloads .. [3] http://stackoverflow.com/questions/16694907/how-to-download-large-file-in-python-with-requests-py .. [4] https://github.com/pytorch/pytorch/blob/2787f1d8edbd4aadd4a8680d204341a1d7112e2d/torch/hub.py#L347 TODO: - [ ] fine-grained control of progress Example: >>> # xdoctest: +REQUIRES(--network) >>> from ubelt.util_download import * # NOQA >>> url = 'http://i.imgur.com/rqwaDag.png' >>> fpath = download(url) >>> print(basename(fpath)) rqwaDag.png Example: >>> # xdoctest: +REQUIRES(--network) >>> import ubelt as ub >>> import io >>> url = 'http://i.imgur.com/rqwaDag.png' >>> file = io.BytesIO() >>> fpath = download(url, file) >>> file.seek(0) >>> data = file.read() >>> assert ub.hash_data(data, hasher='sha1').startswith('f79ea24571') Example: >>> # xdoctest: +REQUIRES(--network) >>> url = 'http://i.imgur.com/rqwaDag.png' >>> fpath = download(url, hasher='sha1', hash_prefix='f79ea24571da6ddd2ba12e3d57b515249ecb8a35') Downloading url='http://i.imgur.com/rqwaDag.png' to fpath=...rqwaDag.png ... ...1233/1233... rate=... Hz, eta=..., total=..., wall=... Example: >>> # xdoctest: +REQUIRES(--network) >>> # test download from girder >>> import pytest >>> import ubelt as ub >>> url = 'https://data.kitware.com/api/v1/item/5b4039308d777f2e6225994c/download' >>> ub.download(url, hasher='sha512', hash_prefix='c98a46cb31205cf') >>> with pytest.raises(RuntimeError): >>> ub.download(url, hasher='sha512', hash_prefix='BAD_HASH') """ from ubelt import ProgIter as Progress from ubelt import ensure_app_cache_dir import shutil import tempfile import hashlib if six.PY2: # nocover from urllib2 import urlopen # NOQA else: from urllib.request import urlopen # NOQA if fpath is None: dpath = ensure_app_cache_dir('ubelt') fname = basename(url) fpath = join(dpath, fname) _dst_is_io_object = hasattr(fpath, 'write') if verbose: if _dst_is_io_object: print('Downloading url=%r to IO object' % (url,)) else: print('Downloading url=%r to fpath=%r' % (url, fpath)) urldata = urlopen(url) meta = urldata.info() try: if hasattr(meta, 'getheaders'): # nocover file_size = int(meta.getheaders("Content-Length")[0]) else: file_size = int(meta.get_all("Content-Length")[0]) except Exception: # nocover # sometimes the url does not contain content length metadata # TODO: find a public URL that exemplifies this or figure out how to # mock it locally. file_size = None if hash_prefix: if isinstance(hasher, six.string_types): if hasher == 'sha1': hasher = hashlib.sha1() elif hasher == 'sha512': hasher = hashlib.sha512() else: raise KeyError(hasher) if _dst_is_io_object: _file_write = fpath.write else: tmp = tempfile.NamedTemporaryFile(delete=False) _file_write = tmp.write # possible optimization (have not tested or timed) _urldata_read = urldata.read try: with Progress(total=file_size, disable=not verbose) as pbar: _pbar_update = pbar.update def _critical_loop(): # Initialize the buffer to a non-empty object buffer = ' ' if hash_prefix: _hasher_update = hasher.update while buffer: buffer = _urldata_read(chunksize) _file_write(buffer) _hasher_update(buffer) _pbar_update(len(buffer)) else: # Same code as above, just without the hasher update. # (tight loop optimization: remove in-loop conditional) while buffer: buffer = _urldata_read(chunksize) _file_write(buffer) _pbar_update(len(buffer)) _critical_loop() if not _dst_is_io_object: tmp.close() # We keep a potentially corrupted file if the hash doesn't match. # It could be the case that the user simply specified the wrong # hash_prefix. shutil.move(tmp.name, fpath) if hash_prefix: got = hasher.hexdigest() if got[:len(hash_prefix)] != hash_prefix: print('hash_prefix = {!r}'.format(hash_prefix)) print('got = {!r}'.format(got)) if _dst_is_io_object: raise RuntimeError( 'invalid hash value ' '(expected "{}", got "{}")'.format(hash_prefix, got)) else: raise RuntimeError( 'invalid hash value for fpath={!r} ' '(expected "{}", got "{}")'.format( fpath, hash_prefix, got)) finally: if not _dst_is_io_object: # nocover tmp.close() # If for some reason the move failed, delete the temporary file if exists(tmp.name): os.remove(tmp.name) return fpath
[docs]def grabdata(url, fpath=None, dpath=None, fname=None, redo=False, verbose=1, appname=None, hash_prefix=None, hasher='sha512', **download_kw): """ Downloads a file, caches it, and returns its local path. If unspecified the location and name of the file is chosen automatically. A hash_prefix can be specified to verify the integrity of the downloaded data. Args: url (str): url to the file to download fpath (PathLike): The full path to download the file to. If unspecified, the arguments `dpath` and `fname` are used to determine this. dpath (PathLike): where to download the file. If unspecified `appname` is used to determine this. Mutually exclusive with fpath. fname (str): What to name the downloaded file. Defaults to the url basename. Mutually exclusive with fpath. redo (bool, default=False): if True forces redownload of the file verbose (bool, default=True): verbosity flag appname (str): set dpath to `ub.get_app_cache_dir(appname)`. Mutually exclusive with dpath and fpath. hash_prefix (None | str): If specified, grabdata verifies that this matches the hash of the file, and then saves the hash in a adjacent file to certify that the download was successful. Defaults to None. hasher (str | Hasher): If hash_prefix is specified, this indicates the hashing algorithm to apply to the file. Defaults to sha512. **download_kw: additional kwargs to pass to ub.download Returns: PathLike: fpath - path to downloaded or cached file. Example: >>> # xdoctest: +REQUIRES(--network) >>> import ubelt as ub >>> url = 'http://i.imgur.com/rqwaDag.png' >>> fpath = ub.grabdata(url, fname='mario.png') >>> result = basename(fpath) >>> print(result) mario.png Example: >>> # xdoctest: +REQUIRES(--network) >>> import ubelt as ub >>> fname = 'foo.bar' >>> url = 'http://i.imgur.com/rqwaDag.png' >>> prefix1 = '944389a39dfb8fa9' >>> fpath = ub.grabdata(url, fname=fname, hash_prefix=prefix1) >>> stamp_fpath = fpath + '.hash' >>> assert open(stamp_fpath, 'r').read() == prefix1 >>> # Check that the download doesn't happen again >>> fpath = ub.grabdata(url, fname=fname, hash_prefix=prefix1) >>> # todo: check file timestamps have not changed >>> # >>> # Check redo works with hash >>> fpath = ub.grabdata(url, fname=fname, hash_prefix=prefix1, redo=True) >>> # todo: check file timestamps have changed >>> # >>> # Check that a redownload occurs when the stamp is changed >>> open(stamp_fpath, 'w').write('corrupt-stamp') >>> fpath = ub.grabdata(url, fname=fname, hash_prefix=prefix1) >>> assert open(stamp_fpath, 'r').read() == prefix1 >>> # >>> # Check that a redownload occurs when the stamp is removed >>> ub.delete(stamp_fpath) >>> open(fpath, 'w').write('corrupt-data') >>> assert not ub.hash_file(fpath, base='hex', hasher='sha512').startswith(prefix1) >>> fpath = ub.grabdata(url, fname=fname, hash_prefix=prefix1) >>> assert ub.hash_file(fpath, base='hex', hasher='sha512').startswith(prefix1) >>> # >>> # Check that requesting new data causes redownload >>> url2 = 'https://data.kitware.com/api/v1/item/5b4039308d777f2e6225994c/download' >>> prefix2 = 'c98a46cb31205cf' >>> fpath = ub.grabdata(url2, fname=fname, hash_prefix=prefix2) >>> assert open(stamp_fpath, 'r').read() == prefix2 """ from ubelt.util_platform import ensure_app_cache_dir if appname and dpath: raise ValueError('Cannot specify appname with dpath') if fpath and (dpath or fname or appname): raise ValueError('Cannot specify fpath with dpath or fname') if fpath is None: if dpath is None: appname = appname or 'ubelt' dpath = ensure_app_cache_dir(appname) if fname is None: fname = basename(url) fpath = join(dpath, fname) # note that needs_download is never set to false after it becomes true # this is the key to working through the logic of the following checks needs_download = redo if not exists(fpath): # always download if we are missing the file needs_download = True if hash_prefix: stamp_fpath, needs_download = _check_hash_stamp( fpath, hash_prefix, hasher, verbose, needs_download) if needs_download: fpath = download(url, fpath, verbose=verbose, hash_prefix=hash_prefix, hasher=hasher, **download_kw) if hash_prefix: # If the file successfully downloaded then the hashes match. # write out the expected prefix so we can check it later with open(stamp_fpath, 'w') as file: file.write(hash_prefix) else: if verbose >= 2: print('Already have file %s' % fpath) return fpath
def _check_hash_stamp(fpath, hash_prefix, hasher, verbose, needs_download=False): stamp_fpath = fpath + '.hash' # Force a re-download if the hash file does not exist or it does # not match the expected hash if exists(stamp_fpath): with open(stamp_fpath, 'r') as file: hashstr = file.read() if not hashstr.startswith(hash_prefix): if verbose: # pragma: nobranch print('invalid hash value (expected "{}", got "{}")'.format( hash_prefix, hashstr)) needs_download = True elif exists(fpath): # If the file exists, but the hash doesnt exist, simply compute the # hash of the existing file instead of redownloading it. # Redownload if this fails. from ubelt import util_hash hashstr = util_hash.hash_file(fpath, hasher=hasher) if hashstr.startswith(hash_prefix): # Write the missing stamp file if it matches with open(stamp_fpath, 'w') as file: file.write(hash_prefix) else: if verbose: # pragma: nobranch print('invalid hash value (expected "{}", got "{}")'.format( hash_prefix, hashstr)) needs_download = True else: needs_download = True return stamp_fpath, needs_download