def update_image_storage():
"""This operation should clear DB if run multiple times on the same DB
8 Points: 3 for xpath (1 each), 1 for correct resource GET, 2 for correct DB entry handling,
2 for correct regex, 2 for Transaction explanation
-0.5 for small mistakes (return value...)
:return: json if successful or not
"""
# TODO get BASE_URL_DATASET, we would suggest requests for it (already installed) Think about error handling.
answer = requests.get(BASE_URL_DATASET)
# Error handling
# TODO Please explain what this line is doing. Why is it needed? In which case? (directly here as comment)
with database_holder.database.transaction():
# Empty databases
Image.delete().execute() # pylint: disable=no-value-for-parameter
Caption.delete().execute() # pylint: disable=no-value-for-parameter
# TODO We encourage you to use the html.fromstring method provided by the lxml package (already installed).
tree = None
# TODO After parsing the XML tree, please use the xpath method to iterate over all elements
for pictureTree in tree.xpath(''):
# TODO get image src by xpath method, you can check lxml documentation or use a debugger to find attributes
src = None
# TODO parse category by appling a regex to src, probably check out regex101.com
# check out re docs of Python3
category = None
# save Image in DB, nothing magical here
imageDb = Image(src=src, category=category)
imageDb.save()
# TODO iterate over all captions by using xpath method. Try to make the xpath expression as short as
# possible
for captionTree in []:
caption_text = ''
Caption(text=caption_text, image=imageDb).save()
return json.dumps({'status': 'finished'}), 200
def update_image_storage():
"""This operation should clear DB if run multiple times on the same DB
8 Points: 3 for xpath (1 each), 1 for correct resource GET, 2 for correct DB handling,
1 for correct regex, 1 for Transaction explanation
-0.5 for small mistakes (return value...)
:return: json if successful or not
"""
answer = requests.get(BASE_URL_DATASET)
# Error handling
answer.raise_for_status()
# This line starts a new transaction and automatically commits it at the end of the with-clause
# It is needed because database operations can fail. Then, the transaction would have to be aborted.
# The with-clause also takes care of this and issues a rollback.
with database_holder.database.transaction():
# Empty databases
Image.delete().execute() # pylint: disable=no-value-for-parameter
Caption.delete().execute() # pylint: disable=no-value-for-parameter
tree = html.fromstring(answer.text)
# for every picture (corresponds to tr)
for pictureTree in tree.xpath('/html/body/table/tr'):
# get source and category
src = pictureTree.xpath('td/img/@src')[0]
category = re.match(r'(\w+)\/', src).group(1)
# save Image in DB, nothing magical here
imageDb = Image(src=src, category=category)
imageDb.save()
# get all captions and save them
for captionTree in pictureTree.xpath('td//td'):
caption_text = captionTree.text[1:]
Caption(text=caption_text, image=imageDb).save()
return json.dumps({'status': 'finished'}), 200
def update_image_storage():
"""This operation should clear DB if run multiple times on the same DB
8 Points: 3 for xpath (1 each), 1 for correct resource GET, 1 for correct DB cleaning, 1 for correct DB saving,
2 for correct regex, 2 for Transaction explanation
-0.5 for small mistakes (return value...)
:return: json if successful or not
"""
# TODO get BASE_URL_DATASET, we would suggest requests for it (already installed) Think about error handling.
try:
page = requests.get(BASE_URL_DATASET)
except requests.exceptions.Timeout:
print('A timeout occured.')
# Maybe set up for a retry, or continue in a retry loop
except requests.exceptions.TooManyRedirects:
print('Too many redirects were made.')
# Tell the user their URL was bad and try a different one
except requests.exceptions.RequestException as e:
print('An error occured', e)
# catastrophic error. bail.
sys.exit(1)
# TODO Please explain what this line is doing. Why is it needed? In which case? (directly here as comment)
# The `with` keyword guarantees that some cleanup routine for the to-be-executed routine is implicitly run
# after the scope exits. In this particular case, the clean-up-routine is the return statement, such that
# the 'status': 'finished' value is guaranteed to be sent together with the 200 status code.
with database_holder.database.transaction():
# Empty databases
Image.delete().execute() # pylint: disable=no-value-for-parameter
Caption.delete().execute() # pylint: disable=no-value-for-parameter
# TODO We encourage you to use the html.fromstring method provided by the lxml package (already installed).
tree = html.fromstring(page.text)
# "status": "/html/body/table/tr[1000]/td[2]/table/tr[5]/td"
pictureTrees = tree.xpath('/html/body/table/tr');
# TODO After parsing the XML tree, please use the xpath method to iterate over all elements
for index, pictureTree in enumerate(pictureTrees, start=1):
# print('processing pictureTree #', index);
# Extract the source attribute
src = next(iter(pictureTree.xpath('td[1]/img/@src')), None)
if src == None:
continue # skip entry if no image is in row
# print('src is ', src);
# Take only substring with category descriptor
category = re.match('^(\w.*)\/', src).group(1)
if category == None:
continue # skip entry if category could can't be extracted
# print('category is ', category);
# Save Image in DB, nothing magical here
imageDb = Image(src=src, category=category)
imageDb.save()
# print('saved image entry!');
# Save the captions additionally
for captionTree in pictureTree.xpath('td[2]/table/*/td/text()'):
# Remove whitespaces on edges
caption_text = captionTree.strip()
Caption(text=caption_text, image=imageDb).save()
# print('Added caption', caption_text);
return json.dumps({'status': 'finished'}), 200