Problems with Python in Google App Engine - UTF-8

2019-08-31 18:04发布

站内问答 / Python
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So for the past few days I've been trying to learn Python in App Engine. However, I've been encountering a number of problems with ASCII and UTF encoding. The freshest issue is as follows:

I have the following piece of code of a simplistic chatroom from the book 'Code in the Cloud'

from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
import datetime


# START: MainPage
class ChatMessage(object):
def __init__(self, user, msg):
    self.user = user
    self.message = msg
    self.time = datetime.datetime.now()

def __str__(self):
    return "%s (%s): %s" % (self.user, self.time, self.message)

Messages = []

class ChatRoomPage(webapp.RequestHandler):
def get(self):
    self.response.headers["Content-Type"] = "text/html"
    self.response.out.write("""
       <html>
         <head>
           <title>MarkCC's AppEngine Chat Room</title>
         </head>
         <body>
           <h1>Welcome to MarkCC's AppEngine Chat Room</h1>
           <p>(Current time is %s)</p>
       """ % (datetime.datetime.now()))
    # Output the set of chat messages
    global Messages
    for msg in Messages:
        self.response.out.write("<p>%s</p>" % msg)
    self.response.out.write("""
       <form action="" method="post">
       <div><b>Name:</b> 
       <textarea name="name" rows="1" cols="20"></textarea></div>
       <p><b>Message</b></p>
       <div><textarea name="message" rows="5" cols="60"></textarea></div>
       <div><input type="submit" value="Send ChatMessage"></input></div>
       </form>
     </body>
   </html>
   """)
 # END: MainPage    
 # START: PostHandler
def post(self):
    chatter = self.request.get("name")
    msg = self.request.get("message")
    global Messages
    Messages.append(ChatMessage(chatter, msg))
    # Now that we've added the message to the chat, we'll redirect
    # to the root page, which will make the user's browser refresh to
    # show the chat including their new message.
    self.redirect('/')        
# END: PostHandler




# START: Frame
chatapp = webapp.WSGIApplication([('/', ChatRoomPage)])


def main():
run_wsgi_app(chatapp)

if __name__ == "__main__":
main()
# END: Frame

It works ok in English. However, the moment I add some non-standard characters all sorts of problems start

First of all, in order for the thing to be actually able to display characters in HTML I add meta tag - charset=UTF-8" etc

Curiously, if you enter non-standard letters, the program processes them nicely, and displays them with no issues. However, it fails to load if I enter any non-ascii letters to the web layout iteself withing the script. I figured out that adding utf-8 encoding line would work. So I added (# -- coding: utf-8 --). This was not enough. Of course I forgot to save the file in UTF-8 format. Upon that the program started running.

That would be the good end to the story, alas....

It doesn't work

Long story short this code:

# -*- coding: utf-8 -*-
from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app
import datetime


# START: MainPage
class ChatMessage(object):
def __init__(self, user, msg):
    self.user = user
    self.message = msg
    self.time = datetime.datetime.now()

def __str__(self):
    return "%s (%s): %s" % (self.user, self.time, self.message)

Messages = []
class ChatRoomPage(webapp.RequestHandler):
def get(self):
    self.response.headers["Content-Type"] = "text/html"
    self.response.out.write("""
       <html>
         <head>
           <title>Witaj w pokoju czatu MarkCC w App Engine</title>
           <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
         </head>
         <body>
           <h1>Witaj w pokoju czatu MarkCC w App Engine</h1>
           <p>(Dokladny czas Twojego logowania to: %s)</p>
       """ % (datetime.datetime.now()))
    # Output the set of chat messages
    global Messages
    for msg in Messages:
        self.response.out.write("<p>%s</p>" % msg)
    self.response.out.write("""
       <form action="" method="post">
       <div><b>Twój Nick:</b> 
       <textarea name="name" rows="1" cols="20"></textarea></div>
       <p><b>Twoja Wiadomość</b></p>
       <div><textarea name="message" rows="5" cols="60"></textarea></div>
       <div><input type="submit" value="Send ChatMessage"></input></div>
       </form>
     </body>
   </html>
   """)
# END: MainPage    
# START: PostHandler
def post(self):
    chatter = self.request.get(u"name")
    msg = self.request.get(u"message")
    global Messages
    Messages.append(ChatMessage(chatter, msg))
    # Now that we've added the message to the chat, we'll redirect
    # to the root page, which will make the user's browser refresh to
    # show the chat including their new message.
    self.redirect('/')        
# END: PostHandler




# START: Frame
chatapp = webapp.WSGIApplication([('/', ChatRoomPage)])


def main():
run_wsgi_app(chatapp)

if __name__ == "__main__":
main()
# END: Frame

Fails to process anything I write in the chat application when it's running. It loads but the moment I enter my message (even using only standard characters) I receive 

File "D:\Python25\lib\StringIO.py", line 270, in getvalue
self.buf += ''.join(self.buflist)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 64: ordinal not in       range(128)

error message. In other words, if I want to be able to use any characters within the application I cannot put non-English ones in my interface. Or the other way round, I can use non-English characters within the app only if I don't encode the file in utf-8. How to make it all work together?

2条回答
三岁会撩人
2楼-- · 2019-08-31 18:21

Your strings contain unicode characters, but they're not unicode strings, they're byte strings. You need to prefix each one with u (as in u"foo") in order to make them into unicode strings. If you ensure all your strings are Unicode strings, you should eliminate that error.

You should also specify the encoding in the Content-Type header rather than a meta tag, like this:

self.response.headers['Content-Type'] = 'text/html; charset=UTF-8'

Note your life would be a lot easier if you used a templating system instead of writing HTML inline with your Python code.

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Anthone
3楼-- · 2019-08-31 18:23

@Thomas K. Thank you for your guidance here. Thanks to you I was able to come up with, maybe - as you said - a little roudabout solution - so the credit for the answer should go to you. The following line of code:

Messages.append(ChatMessage(chatter, msg))

Should look like this: 

Messages.append(ChatMessage(chatter.encode( "utf-8" ), msg.encode( "utf-8" )))

Basically I have to encode all the utf-8 string to ascii.

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