Question

I have added some functionality to the gae-sessions library, so that I can have flash data; That means, data that only exists between 2 requests of a certain user. Here is the code I added:

def set_flashdata(key,val=None):
    logging.info('set flashdata '+key+'='+val )
    sess = get_current_session()
    if val:
        sess['flash_'+key]=val
        return
    for x in key:
        sess['flash_'+x]=key[x]

def get_flashdata():
    sess = get_current_session()
    flash = {}
    for key in sess:
        if(key.startswith("flash_")):
            flash[key[6:]]=sess.pop(key)
            logging.info('received flashdata '+key+'='+sess[key])
    logging.info('fetched '+str(len(flash))+' flash items')
    return flash

def has_flashdata():
    sess = get_current_session()
    for key in sess:
        if key.startswith('flash_'):
            return True
    return False

but when I run get_flashdata, I get this:

File "/Users/frederikcreemers/Documents/projects/web/myproject/gaesessions/__init__.py", line 533, in get_flashdata
    logging.info('received flashdata '+key+'='+sess[key])
File "/Users/frederikcreemers/Documents/projects/web/myproject/gaesessions/__init__.py", line 393, in __getitem__
    return self.data.__getitem__(key)
KeyError: 'flash_msg_type'

so, the program sais that the key mg_type is not in sess, but since I’m iterating over the keys of sess, it must be in there.

Answer 1

In the line above, you’ve called pop which removes the item from the dictionary.