Google App Engine | Chris' Laboratory

Python – ImportError: No module named django.utils

By Chris Lee

19/04/2013

When I follow the tutorial – App Engine Series #4 – I got this error for Ajax.py:

ImportError: No module named django.utils

1	ImportError: No module named django.utils

According to this article, Python 2.7 uses native JSON library. Fixed source for Ajax.py is this:

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# Including the models:
from models.models import *

# from Phyton 2.7, use native JSON library
import json

from datetime import datetime,timedelta
from google.appengine.ext import webapp, db
from google.appengine.api import memcache

# The AJAX controllers:

class TwentyFourHours(webapp.RequestHandler):
    def get(self):

        # This class selects the response times
        # for the last 24 hours.

        # Checking whether the result of this
        # function is already cached in memcache:
        jsonStr = memcache.get("TwentyFourHoursCache")

        # If it is not, we need to generate it:
        if jsonStr is None:

            query = db.GqlQuery("SELECT * FROM Ping WHERE date>:dt ORDER BY date",
                        dt=(datetime.now() - timedelta(hours = 24)))

            results = query.fetch(limit=300)
            chart = []
            for Ping in results:
                chart.append({
                    "label": Ping.date.strftime("%H:%M"),
                    "value": Ping.responseTime
                })

            jsonStr = json.dumps({
                "chart"        : {
                    # tooltip is used by the jQuery chart:
                    "tooltip"    : "Response time at %1: %2ms",
                    "data"        : chart
                },
                "downtime"    : getDowntime(1)
            })

            # Caching it for five minutes:
            memcache.add("TwentyFourHoursCache", jsonStr, 300)

        self.response.out.write(jsonStr);

class SevenDays(webapp.RequestHandler):
    days = 7
    def get(self):

        # Selecting the response times for the last seven days:
        query = db.GqlQuery("SELECT * FROM Day WHERE date>:dt ORDER BY date",
                dt=(datetime.now() - timedelta(days = self.days)))

        results = query.fetch(limit=self.days)
        chart = []
        for Day in results:
            chart.append({
                "label": Day.date.strftime("%b, %d"),
                "value": Day.averageResponseTime
            })

        self.response.out.write(json.dumps({
            "chart"        : {
                "tooltip"    : "Average response time for %1: %2ms",
                "data"        : chart
            },
            "downtime"    : getDowntime(self.days)
        }))

# Extending the SevenDays class and only
# increasing the days member:

class ThirtyDays(SevenDays):
    days = 30

def getDowntime(days=1):

    # Checking whether the result of this function
    # already exists in memcache. Notice the key for get():

    downTimeList = memcache.get("DownTimeCache"+str(days))
    if downTimeList is None:

        query = db.GqlQuery("SELECT * FROM DownTime WHERE date>:dt ORDER BY date",
                dt=(datetime.now() - timedelta(days = days)))

        results = query.fetch(limit=100)

        downTimeList = []
        downTimePeriod = {}

        if len(results) == 0:
            return []

        # This loop "compacts" the downtime:

        for DownTime in results:

            if not downTimePeriod.has_key("begin"):
                downTimePeriod = {"begin":DownTime.date,"end":DownTime.date}
                continue

            if DownTime.date - downTimePeriod['end'] < timedelta(minutes=8):                 downTimePeriod['end'] = DownTime.date             else:                 downTimeList.append(downTimePeriod)                 downTimePeriod = {"begin":DownTime.date,"end":DownTime.date}         downTimeList.append(downTimePeriod)         # Formatting the output of this function:         for i in downTimeList:             if i['end'] + timedelta(minutes=5) > datetime.now():
                i['period'] = timedeltaFormat(((datetime.now() - i['begin'])).seconds)
                i['end'] = "NOW"
            else:
                i['period'] = timedeltaFormat(((i['end'] - i['begin']) + timedelta(minutes=5)).seconds)
                i['end'] = (i['end']+timedelta(minutes=5)).strftime('%H:%M on %b, %d, %Y')    

            i['begin'] = i['begin'].strftime('%H:%M on %b, %d, %Y')

        # Storing the response in memcache:
        memcache.add("DownTimeCache"+str(days), downTimeList, 300)

    return downTimeList

# A helper function for formatting time periods.

def timedeltaFormat(seconds):
    hours, remainder = divmod(seconds, 3600)
    minutes, seconds = divmod(remainder, 60)

    return ('%02d:%02d:%02d' % (hours, minutes, seconds))

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#!/usr/bin/env python

# -*- coding: utf-8 -*-

# Including the models:

from models.models import *

# from Phyton 2.7, use native JSON library

import json

from datetime import datetime,timedelta

from google.appengine.ext import webapp, db

from google.appengine.api import memcache

# The AJAX controllers:

class TwentyFourHours(webapp.RequestHandler):

def get(self):

# This class selects the response times

# for the last 24 hours.

# Checking whether the result of this

# function is already cached in memcache:

jsonStr = memcache.get("TwentyFourHoursCache")

# If it is not, we need to generate it:

if jsonStr is None:

query = db.GqlQuery("SELECT * FROM Ping WHERE date>:dt ORDER BY date",

dt=(datetime.now() - timedelta(hours = 24)))

results = query.fetch(limit=300)

chart = []

for Ping in results:

chart.append({

"label": Ping.date.strftime("%H:%M"),

"value": Ping.responseTime

})

jsonStr = json.dumps({

"chart" : {

# tooltip is used by the jQuery chart:

"tooltip" : "Response time at %1: %2ms",

"data" : chart

"downtime" : getDowntime(1)

})

# Caching it for five minutes:

memcache.add("TwentyFourHoursCache", jsonStr, 300)

self.response.out.write(jsonStr);

class SevenDays(webapp.RequestHandler):

days = 7

def get(self):

# Selecting the response times for the last seven days:

query = db.GqlQuery("SELECT * FROM Day WHERE date>:dt ORDER BY date",

dt=(datetime.now() - timedelta(days = self.days)))

results = query.fetch(limit=self.days)

chart = []

for Day in results:

chart.append({

"label": Day.date.strftime("%b, %d"),

"value": Day.averageResponseTime

})

self.response.out.write(json.dumps({

"chart" : {

"tooltip" : "Average response time for %1: %2ms",

"data" : chart

"downtime" : getDowntime(self.days)

}))

# Extending the SevenDays class and only

# increasing the days member:

class ThirtyDays(SevenDays):

days = 30

def getDowntime(days=1):

# Checking whether the result of this function

# already exists in memcache. Notice the key for get():

downTimeList = memcache.get("DownTimeCache"+str(days))

if downTimeList is None:

query = db.GqlQuery("SELECT * FROM DownTime WHERE date>:dt ORDER BY date",

dt=(datetime.now() - timedelta(days = days)))

results = query.fetch(limit=100)

downTimeList = []

downTimePeriod = {}

if len(results) == 0:

return []

# This loop "compacts" the downtime:

for DownTime in results:

if not downTimePeriod.has_key("begin"):

downTimePeriod = {"begin":DownTime.date,"end":DownTime.date}

continue

if DownTime.date - downTimePeriod['end'] < timedelta(minutes=8): downTimePeriod['end'] = DownTime.date else: downTimeList.append(downTimePeriod) downTimePeriod = {"begin":DownTime.date,"end":DownTime.date} downTimeList.append(downTimePeriod) # Formatting the output of this function: for i in downTimeList: if i['end'] + timedelta(minutes=5) > datetime.now():

i['period'] = timedeltaFormat(((datetime.now() - i['begin'])).seconds)

i['end'] = "NOW"

else:

i['period'] = timedeltaFormat(((i['end'] - i['begin']) + timedelta(minutes=5)).seconds)

i['end'] = (i['end']+timedelta(minutes=5)).strftime('%H:%M on %b, %d, %Y')

i['begin'] = i['begin'].strftime('%H:%M on %b, %d, %Y')

# Storing the response in memcache:

memcache.add("DownTimeCache"+str(days), downTimeList, 300)

return downTimeList

# A helper function for formatting time periods.

def timedeltaFormat(seconds):

hours, remainder = divmod(seconds, 3600)

minutes, seconds = divmod(remainder, 60)

return ('%02d:%02d:%02d' % (hours, minutes, seconds))

Python – ImportError: No module named

By Chris Lee

19/04/2013

| No Comments

| Development, Google App Engine

When I follow the tutorial – App Engine Series #4 – I kept getting the error like below:

ImportError: No module named controllers

1	ImportError: No module named controllers

It is caused by below code:

import webapp2

# Importing the controllers that will handle
# the generation of the pages:
from controllers import crons,ajax,generate,mainh

import webapp2

# Importing the controllers that will handle

# the generation of the pages:

from controllers import crons,ajax,generate,mainh

To fix the error, it is very simple. Just create empty ‘__init__.py’ file in ‘controllers’ folder without content. You will need to create on ‘config’, ‘models’ folders as well. Once […]

Google App Engine Tutorial – Datastore – 한글 입력시 Internal Server Error 나는 현상

By Chris Lee

18/04/2013

| No Comments

| Development, Google App Engine

Google App Engine의 Datastore 튜토리얼 소스를 실행시 한글을 방명록 이름(Guestbook name)필드에 입력하면 다음과 같은 에러가 발생한다.

Traceback (most recent call last):
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1535, in __call__
    rv = self.handle_exception(request, response, e)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1529, in __call__
    rv = self.router.dispatch(request, response)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
    return route.handler_adapter(request, response)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1102, in __call__
    return handler.dispatch()
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 572, in dispatch
    return self.handle_exception(e, self.app.debug)
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 570, in dispatch
    return method(*args, **kwargs)
  File "/Applications/MAMP/htdocs/google_app_engines/datastore/main.py", line 65, in get
    sign_query_params = urllib.urlencode({'guestbook_name': guestbook_name})
  File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/dist27/urllib.py", line 1307, in urlencode
    v = quote_plus(str(v))
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-2: ordinal not in range(128)

Traceback (most recent call last):

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1535, in __call__

rv = self.handle_exception(request, response, e)

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1529, in __call__

rv = self.router.dispatch(request, response)

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher

return route.handler_adapter(request, response)

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 1102, in __call__

return handler.dispatch()

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 572, in dispatch

return self.handle_exception(e, self.app.debug)

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/webapp2-2.5.2/webapp2.py", line 570, in dispatch

return method(*args, **kwargs)

File "/Applications/MAMP/htdocs/google_app_engines/datastore/main.py", line 65, in get

sign_query_params = urllib.urlencode({'guestbook_name': guestbook_name})

File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/dist27/urllib.py", line 1307, in urlencode

v = quote_plus(str(v))

UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-2: ordinal not in range(128)

UnicodeEncodeError: ‘ascii’ codec can’t encode characters in position 0-2: ordinal not in range(128) 위 에러가 발생하는데, 이걸 해결하기 위해 다음과 같은 글을 찾았고, 한글 입력시에도 방명록 이름 바꾸는게 가능하게 되었다.

class Greeting(db.Model):
    """Models an individual Guestbook entry with author, content, and date."""
    author = db.StringProperty()
    content = db.StringProperty(multiline=True) # multipe lines
    date = db.DateTimeProperty(auto_now_add=True)   # add now time value automatically

def guestbook_key(guestbook_name=None):
    """Constructs a Datastore key for a Guestbook entity with guestbook_name."""
    guestbook_name = guestbook_name.decode("utf-8")
    return db.Key.from_path('Guestbook', guestbook_name or 'default_guestbook')

class MainPage(webapp2.RequestHandler):

    def get(self):
        self.response.write('')
        guestbook_name = self.request.get('guestbook_name').encode("utf-8")

        # Ancestor Queries, as shown here, are strongly consistent with the High
        # Replication Datastore. Queries that span entity groups are eventually
        # consistent. If we omitted the ancestor from this query there would be
        # a slight chance that Greeting that had just been written would not
        # show up in a query.

        greetings = db.GqlQuery("SELECT * "
                                "FROM Greeting "
                                "WHERE ANCESTOR IS :1 "
                                "ORDER BY date DESC LIMIT 10",
                                guestbook_key(guestbook_name))

        for greeting in greetings:
            if greeting.author:
                self.response.write(
                    '<b>%s</b> wrote:' % greeting.author)
            else:
                self.response.write('An anonymous person wrote:')
            self.response.write('%s' %
                                    cgi.escape(greeting.content))

        # Write the submission form and the footer of the page
        sign_query_params = urllib.urlencode({'guestbook_name': guestbook_name})
        self.response.write(MAIN_PAGE_FOOTER_TEMPLATE %
                            (sign_query_params, cgi.escape(guestbook_name)))

# /sign
class Guestbook(webapp2.RequestHandler):

    def post(self):
        # We set the same parent key on the 'Greeting' to ensure each greeting
        # is in the same entity group. Queries across the single entity group
        # will be consistent. However, the write rate to a single entity group
        # should be limited to ~1/second.

        guestbook_name = self.request.get('guestbook_name').encode("utf-8")
        greeting = Greeting(parent=guestbook_key(guestbook_name))

        if users.get_current_user():
            greeting.author = users.get_current_user().nickname()

        greeting.content = self.request.get('content')
        greeting.put()

        query_params = {'guestbook_name': guestbook_name}
        # urllib.urlencode : GET 문자열로 변환해줌 
        self.redirect('/?' + urllib.urlencode(query_params))

app = webapp2.WSGIApplication([('/', MainPage),
                               ('/sign', Guestbook)],
                              debug=True)

class Greeting(db.Model):

"""Models an individual Guestbook entry with author, content, and date."""

author = db.StringProperty()

content = db.StringProperty(multiline=True) # multipe lines

date = db.DateTimeProperty(auto_now_add=True) # add now time value automatically

def guestbook_key(guestbook_name=None):

"""Constructs a Datastore key for a Guestbook entity with guestbook_name."""

guestbook_name = guestbook_name.decode("utf-8")

return db.Key.from_path('Guestbook', guestbook_name or 'default_guestbook')

class MainPage(webapp2.RequestHandler):

def get(self):

self.response.write('')

guestbook_name = self.request.get('guestbook_name').encode("utf-8")

# Ancestor Queries, as shown here, are strongly consistent with the High

# Replication Datastore. Queries that span entity groups are eventually

# consistent. If we omitted the ancestor from this query there would be

# a slight chance that Greeting that had just been written would not

# show up in a query.

greetings = db.GqlQuery("SELECT * "

"FROM Greeting "

"WHERE ANCESTOR IS :1 "

"ORDER BY date DESC LIMIT 10",

guestbook_key(guestbook_name))

for greeting in greetings:

if greeting.author:

self.response.write(

'<b>%s</b> wrote:' % greeting.author)

else:

self.response.write('An anonymous person wrote:')

self.response.write('%s' %

cgi.escape(greeting.content))

# Write the submission form and the footer of the page

sign_query_params = urllib.urlencode({'guestbook_name': guestbook_name})

self.response.write(MAIN_PAGE_FOOTER_TEMPLATE %

(sign_query_params, cgi.escape(guestbook_name)))

# /sign

class Guestbook(webapp2.RequestHandler):

def post(self):

# We set the same parent key on the 'Greeting' to ensure each greeting

# is in the same entity group. Queries across the single entity group

# will be consistent. However, the write rate to a single entity group

# should be limited to ~1/second.

guestbook_name = self.request.get('guestbook_name').encode("utf-8")

greeting = Greeting(parent=guestbook_key(guestbook_name))

if users.get_current_user():

greeting.author = users.get_current_user().nickname()

greeting.content = self.request.get('content')

greeting.put()

query_params = {'guestbook_name': guestbook_name}

# urllib.urlencode : GET 문자열로 변환해줌

self.redirect('/?' + urllib.urlencode(query_params))

app = webapp2.WSGIApplication([('/', MainPage),

('/sign', Guestbook)],

debug=True)

import 및 템플릿 코드는 위에서 제외됨.

Python – 한글로 주석 남기면 실행 안되는 현상(cannot execute app if write Korean as comment)

By Chris Lee

18/04/2013

| No Comments

| Development, Google App Engine

한글로 코멘트를 남겼는데 다음과 같은 서버 에러가 발생했다.

HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

1	HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

검색해서 Using Python with Chinese, Japanese and Korean 라는 글을 찾았고, 코드를 다음과 같이 하니 문제없이 실행되었다.

#!/usr/bin/env python
# -*- coding: utf-8 -*-

1 2	#!/usr/bin/env python # -- coding: utf-8 --

Sample Code from Developing and deploying an application on Google App Engine

By Chris Lee

17/04/2013

| No Comments

| Development, Google App Engine

In the video, it provides the code as below

#!/usr/bin/env python

import os
import wsgiref.handlers
from google.appengine.ext import webapp
from google.appengine.ext.webapp import template

class MyHandler(webapp.RequestHandler):
    def get(self):
        self.response.out.write(template.render('main.html', {}))

def main():
    app = webapp.WSGIApplication([
            (r'.*', MyHandler)], debug= True)
    wsgiref.handlers.CGIHandler().run(app);

if __name__ == "__main__":
    main()

#!/usr/bin/env python

import os

import wsgiref.handlers

from google.appengine.ext import webapp

from google.appengine.ext.webapp import template

class MyHandler(webapp.RequestHandler):

def get(self):

self.response.out.write(template.render('main.html', {}))

def main():

app = webapp.WSGIApplication([

(r'.*', MyHandler)], debug= True)

wsgiref.handlers.CGIHandler().run(app);

if __name__ == "__main__":

main()

However, it gives the error as below:

Traceback (most recent call last):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/wsgiref/handlers.py", line 86, in run
    self.finish_response()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/wsgiref/handlers.py", line 127, in finish_response
    self.write(data)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/wsgiref/handlers.py", line 202, in write
    assert type(data) is StringType,"write() argument must be string"
AssertionError: write() argument must be string

Traceback (most recent call last):

File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/wsgiref/handlers.py", line 86, in run

self.finish_response()

File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/wsgiref/handlers.py", line 127, in finish_response

self.write(data)

File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/wsgiref/handlers.py", line 202, in write

assert type(data) is StringType,"write() argument must be string"

AssertionError: write() argument must be string

To fix this error, I have found this article. According to answer, it is unicode problem. So fixed version of code is below:

#!/usr/bin/env python

import os
import wsgiref.handlers
from google.appengine.ext import webapp
from google.appengine.ext.webapp import template

class MyHandler(webapp.RequestHandler):
    def get(self):
        self.response.out.write(unicode(template.render('main.html', {})))

def main():
    app = webapp.WSGIApplication([
            (r'.*', MyHandler)], debug= True)
    wsgiref.handlers.CGIHandler().run(app);

if __name__ == "__main__":
    main()

#!/usr/bin/env python

import os

import wsgiref.handlers

from google.appengine.ext import webapp

from google.appengine.ext.webapp import template

class MyHandler(webapp.RequestHandler):

def get(self):

self.response.out.write(unicode(template.render('main.html', {})))

def main():

app = webapp.WSGIApplication([

(r'.*', MyHandler)], debug= True)

wsgiref.handlers.CGIHandler().run(app);

if __name__ == "__main__":

main()

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