Excuse the vague title, I didn't know how else to state this.
I have a task worker request handler that fetches data from a URL and writes it to blobstore and saves the data's blob_key to a ListProperty in datastore. I've tried to simplifly the code for clarity here:
class Fetch(webapp2.RequestHandler):
def get(self):
url = self.request.get('url')
itemKey = self.request.get('itemKey')
item = MyModel.get(itemKey)
try:
result = urlfetch.fetch(url=url)
if result.status_code == 200:
saveDataResult = save_data(result.content, itemKey)
if saveDataResult is False:
raise Exception('error saving data')
else:
raise Exception('error fetching data: %s' % result.status_code)
item.status = 'success'
except Exception:
item.status = 'failed'
finally:
item.put()
def save_data(data, itemKey)
try:
#write data to blobstore and get its blob_key...
blob_key = files.blobstore.get_blob_key(file_name)
item = MyModel.get(itemKey)
item.blobKey.append(blob_key)
item.put()
return True
except:
return False
Now the problem I'm having is, when saveDataResult returns True, its status is set to 'success' but its blobKey property contains no value, even though a blob_key was generated and the data successfully written. I can't see what's causing this to save my life, please help.
Without much more information it is very difficult to determine what's happening. Here's my educated guess:
MyModel.get(itemKey) is called both in get() and save_data(). I surmise that it's returning two different objects representing the item. When the blobKey gets updated in save_data, the update is occurring only in the object fetched in save_data. When you later examine it outside that scope, you're looking at a different object.
Whether this is correct or not will depend on the implementation of MyModel.get().
Also, you do realize that you're calling item.put() twice, right?
The problem is here
finally:
item.put()
this single call overrides the data saved by save_data() because it references an older object of item.
My suggestion would be you do the status updates from save_data() i.e item.status = 'success'
or move item = MyModel.get(itemKey) to come after save_data() so you can fetch the updated object.
The problem is that when you call save_data() with item = MyModel.get(itemKey)
which is again called from the class Fetch you end up having two different objects and therefore overwriting the one in save_data() and hence when you go to your model datastore no data for blobkey is stored as its overwritten.
Try doing everything in the class or you do not use item = MyModel.get(itemKey) twice.
Related
I use SQLFORM.smartgrid to show a list of records from a table (service_types). In each row of the smartgrid there is a delete link/button to delete the record. I want to executive some code before smartgrid/web2py actually deletes the record, for example I want to know if there are child records (services table) referencing this record, and if any, flash a message telling user that record cannot be deleted. How is this done?
db.py
db.define_table('service_types',
Field('type_name', requires=[IS_NOT_EMPTY(), IS_ALPHANUMERIC()]),
format='%(type_name)s',
)
db.define_table('services',
Field('service_name',requires=[IS_NOT_EMPTY(),IS_NOT_IN_DB(db,'services.service_name')]),
Field('service_type','reference service_types',requires=IS_IN_DB(db,db.service_types.id,
'%(type_name)s',
error_message='not in table',
zero=None),
ondelete='RESTRICT',
),
Field('interest_rate','decimal(15,2)',requires=IS_DECIMAL_IN_RANGE(0,100)),
Field('max_term','integer'),
auth.signature,
format='%(service_name)s',
)
db.services._plural='Services'
db.services._singular='Service'
if db(db.service_types).count() < 1:
db.service_types.insert(type_name='Loan')
db.service_types.insert(type_name='Contribution')
db.service_types.insert(type_name='Other')
controller
def list_services():
grid = SQLFORM.smartgrid(db.services
, fields = [db.services.service_name,db.services.service_type]
)
return locals()
view
{{extend 'layout.html'}}
{{=grid}}
There are two options. First, the deletable argument can be a function that takes the Row object of a given record and returns True or False to indicate whether the record is deletable. If it returns False, the "Delete" button will not be shown for that record, nor the delete operation be allowed on the server.
def can_delete(row):
return True if [some condition involving row] else False
grid = SQLFORM.smartgrid(..., deletable=can_delete)
Second, there is an ondelete argument that takes the db Table object and the record ID. It is called right before the delete operation, so to prevent the delete, you can do a redirect within that function:
def ondelete(table, record_id):
record = table(record_id)
if [some condition]:
session.flash = 'Cannot delete this record'
redirect(URL())
grid = SQLFORM.smartgrid(..., ondelete=ondelete)
Note, if the grid is loaded via an Ajax component and its actions are therefore performed via Ajax, using redirect within the ondelete method as shown above will not work well, as the redirect will have no effect and the table row will still be deleted from the grid in the browser (even though the database record was not deleted). In that case, an alternative approach is to return a non-200 HTTP response to the browser, which will prevent the client-side Javascript from deleting the row from the table (the delete happens only on success of the Ajax request). We should also set response.flash instead of session.flash (because we are not redirecting/reloading the whole page):
def ondelete(table, record_id):
record = table(record_id)
if [some condition]:
response.flash = 'Cannot delete this record'
raise HTTP(403)
Note, both the deletable and ondelete arguments can be dictionaries with table names as keys, so you can specify different values for different tables that might be linked from the smartgrid.
Finally, notice the delete URLs look like /appname/list_services/services/delete/services/[record ID]. So, in the controller, you can determine if a delete is being requested by checking if 'delete' in request.args. In that case, request.args[-2:] represents the table name and record ID, which you can use to do any checks.
From Anthony's answer I chose the second option and came up with the following:
def ondelete_service_type(service_type_table, service_type_id):
count = db(db.services.service_type == service_type_id).count()
if count > 0:
session.flash = T("Cant delete")
#redirect(URL('default','list_service_types#'))
else:
pass
return locals()
def list_service_types():
grid = SQLFORM.smartgrid(db.service_types
, fields = [db.service_types.type_name, db.services.service_name]
, ondelete = ondelete_service_type
)
return locals()
But, if I do this...
if count > 0:
session.flash = T("Cant delete")
else:
pass
return locals()
I get this error:
And if I do this:
if count > 0:
session.flash = T("Cant delete")
redirect(URL('default','list_service_types#')) <== please take note
else:
pass
return locals()
I get the flash error message Cant delete but the record appears deleted from the list, and reappears after a page refresh with F5 (apparently because the delete was not allowed in the database, which is intended).
Which one should I fix and how?
Note
If any of these issue is resolved I can accept Anthony's answer.
I have checked few of the answers in SO, but nothing worked for me. I'm still giving the same error:
TypeError: get() takes exactly 3 arguments (2 given)
Can anybody check the following code and let me know what I have done wrong?
my 'views.py' is as follows
def get(self, request, tag):
print("Tag for tagging :")
data_loader = SvnDataLoader()
print("Two :")
ss = SubsystemRevision.get_subsystem_for_tag(tag)
print("Subsystem is %s", ss)
try:
print("inside try")
pr = subprocess.Popen(['perl', './svntasktag.pl', 'ss'], stdout=subprocess.PIPE)
data = pr.communicate()
context = {'data':data}
except TagHistoryMissing:
data = 'Tag is missing.'
except SvnException as e:
data = "Problem while trying to fetch tag-history from svn. Try again later"
#logger.error("SvnException %s while trying to fetch the tag %s" % (str(e), tag.name))
return render_to_response('pai_app/create_tag.html', {'data': data}, context_instance=RequestContext(request))
First of all you should know that self refers to the object itself. You can add another argument and you error will be solved e.g.
def get(self, request, tag, foobar):
...
But it's better to know what arguments you want to have and what you are passing to the function.
The second point is that you are using get() in your views. Usually it is not the good practice to use method names for the functions (we have Model.objects.get()). So it is better to change your function to something like get_tag() to prevent any type of conflicts during development. Don't forget to update your app modules! Good luck!
If your function not in a class,you can use
def get(request, tag):
pass
Because the params self not be used in your function.
In django function views,the first params must be a request obj instance.
I have a class that is taking in an Id and trying to update the variable current_account but when I print out the details of the current_account it hasn't updated.
Anyone got any ideas for this? New to python so might be doing something stupid that I can't see.
class UserData:
def __init__(self, db_conn=None):
if None == db_conn:
raise Exception("DB Connection Required.")
self.db = db_conn
self.set_my_account()
self.set_accounts()
self.set_current_account()
def set_current_account(self, account_id=None):
print account_id
if None == account_id:
self.current_account = self.my_account
else:
if len(self.accounts) > 0:
for account in self.accounts:
if account['_id'] == account_id:
self.current_account = account
print self.current_account['_id']
else:
raise Exception("No accounts available.")
Assume that set_my_account() gets a dictionary of account data and that set_accounts() get a list of dictionaries of account data.
So when I do the following:
user_data = UserData(db_conn=db_conn)
user_data.set_current_account(account_id=account_id)
Where db_conn is a valid database connection and account_id is a valid account id.
I get the following out of the above two lines.
None
518a310356c02c0756764b4e
512754cfc1f3d16c25c350b7
So the None value is from the declaration of the class and then the next two are from the call to set_current_account(). The first id value is what I'm trying to set. The second id value is what was already set from the class __init__() method.
There were a lot of redundancies an un-Pythonic constructions. I cleaned up the code to help me understand what you trying to do.
class UserData(object):
def __init__(self, db_conn):
self.db = db_conn
self.set_my_account()
self.set_accounts()
self.set_current_account()
def set_current_account(self, account_id=None):
print account_id
if account_id is None:
self.current_account = self.my_account
else:
if not self.accounts:
raise Exception("No accounts available.")
for account in self.accounts:
if account['_id'] == account_id:
self.current_account = account
print self.current_account['_id']
user_data = UserData(db_conn)
user_data.set_current_account(account_id)
You used default arguments (db_conn=None) when a call without an explicit argument is invalid. Yes, you can now call __init__(None) but you could also call __init__('Nalum'); you can't protect against everything.
By moving the "No accounts" exception the block fast-fails and you save one level of indention.
The call UserData(db_conn=db_conn) is valid but unecessarily repetitive.
Unfortunately, I still can't figure out what you are trying to accomplish and this is perhaps the largest flaw. Variable names are terribly important for help the reader (which may be the future you) make sense of code. current_account, my_account, account_id and current_account['_id'] so obscure the intention that you should really consider more distinct, informative names.
Figured out what it was.
The data was being changed else where in the code base. It is now working as expected.
Thanks guys for pointing out the Python centric things that I was doing wrong, good to get it.
I am creating a list from some of the model data but I am not doing it correctly, it works but when I refresh the page in the broswer reportResults just gets added to. I hoped it would get garbage collected between requests but obviously I am doing something wrong, any ideas anyone??
Thanks,
Ewan
reportResults = [] #the list that doesn't get collected
def addReportResult(fix,description):
fix.description = description
reportResults.append(fix)
def unitHistory(request,unitid, syear, smonth, sday, shour, fyear, fmonth, fday, fhour, type=None):
waypoints = Fixes.objects.filter(name=(unitid))
waypoints = waypoints.filter(gpstime__range=(awareStartTime, awareEndTime)).order_by('gpstime')[:1000]
if waypoints:
for index in range(len(waypoints)):
...do stuff here selecting some waypoints and generating "description" text
addReportResult(waypointsindex,description) ##append the list with this, adding a text description
return render_to_response('unitHistory.html', {'fixes': reportResults})
You are reusing the same list each time, to fix it you need to restructure your code to create a new list on every request. This can be done in multiple ways and this is one such way:
def addReportResult(reportResults, fix,description):
fix.description = description
reportResults.append(fix)
def unitHistory(request,unitid, syear, smonth, sday, shour, fyear, fmonth, fday, fhour, type=None):
reportResults = [] # Here we create our local list that is recreated each request.
waypoints = Fixes.objects.filter(name=(unitid))
waypoints = waypoints.filter(gpstime__range=(awareStartTime, awareEndTime)).order_by('gpstime')[:1000]
if waypoints:
for index in range(len(waypoints)):
# Do processing
addReportResult(reportResults, waypointsindex, description)
# We pass the list to the function so it can use it.
return render_to_response('unitHistory.html', {'fixes': reportResults})
If the addReportResult stays small you could also inline the description attribute set by removing the call to addReportResult altogether and doing the waypointsindex.description = description at the same position.
Just so you're aware of the life cycle of requests, mod_wsgi will keep a process open to service multiple requests. That process gets recycled every so often but it is definitely not bound to a single request as you've assumed.
That means you need a local list. I would suggest moving the addReportResult function contents directly in-line, but that's not a great idea if it needs to be reusable or if the function is too long. Instead I'd make that function return the item, and you can collect the results locally.
def create_report(fix, description): # I've changed the name to snake_casing
fix.description = description
return fix
def unit_history(request,unitid, syear, smonth, sday, shour, fyear, fmonth, fday, fhour, type=None):
reports = []
waypoints = Fixes.objects.filter(name=(unitid))
waypoints = waypoints.filter(gpstime__range=(awareStartTime, awareEndTime)).order_by('gpstime')[:1000]
if waypoints:
for index in range(len(waypoints)):
report = create_report(waypointsindex, description)
reports.append(report)
return render_to_response('unitHistory.html', {'fixes': reportResults})
I'm trying to patch a testing framework built in python for javascript called mootools-test-runner (i'm a front end developer by day, so my python skills are pretty weak... really weak.)
The use case is we want to be able to make a json request to the server and have it delay x amount of time before it returns -- originally it was written to use a sleep method, but that prevented multiple simultaneous requests. Sooo... after poking around for about a day i arrived at the code below. The problem i'm seeing (although there could well be many problems with my code) is:
The view test_runner.views.echo_json didn't return an HttpResponse object.
if anyone could offer any advice or point me in the right direction I would be super grateful -- thanks!
def echo_json(req, wasDelayed=False):
if req.REQUEST.get('delay') and wasDelayed == False:
sleeper(req, echo_jsonp)
else:
response = {}
callback = req.REQUEST.get('callback', False)
noresponse_eys = ['callback', 'delay']
for key, value in req.REQUEST.items():
if key not in noresponse_keys:
response.update({key: value})
response = simplejson.dumps(response)
if callback:
response = '%s(%s);' % (callback, response)
return HttpResponse(response, mimetype='application/javascript')
def sleeper(req, callback)
delay = float(req.REQUEST.get('delay'))
t = threading.Timer(delay, functools.partial(callback, req, true))
t.start()
Are you sure you want the return statement inside the for key, value loop? You're only allowing a single iteration, and returning.
Also, check the flow of the function. There are cases in which it will return None. Easiest way to do this is printing out your request object and examining it in the cases in which the function doesn't return an HttpResponse object.
See that your function will return None if:
req.request contains the key 'delay' and wasDelayed is True
req.REQUEST.items() is empty
I can't be sure, but I think the 2 problems are the else: and the return there. Shouldn't the code below the else: be executing whether the response is delayed or not? And shouldn't the return statement be outside the for loop?