Question

Python Shell – shell.appspot.com is acting weird? or am I missing something?

Google App Engine/1.3.0
Python 2.5.2 (r252:60911, Apr  7 2009, 17:42:26) 
[GCC 4.1.0]

>>> mycolors = ['red','green','blue']
>>> mycolors.append('black')
>>> print mycolors
['red', 'green', 'blue']

But the below result is expected

['red', 'green', 'blue', 'black']

And also same with the dictionary data type.

Thanks,

Abhinay

Answer 1

Short Answer

That is a known bug. Short answer:

• Include everything on one line: mycolors.append('black'); print mycolors
• Use my free software tool, App Engine Console. My code is derived from the shell and I have fixed this bug.

Long answer

The bug involves the way that state is stored in between every command you type. Web requests are stateless and request/response only; however the shell (and my console app) is supposed to feel like a stream of consciousness as it is at the traditional Python prompt.

The implementation is roughly this:

1. Get a request from a browser which includes a line to execute
2. Pull up the specific session which the browser is “in”. Basically that is a module similar to __main__ with some variable bindings.
3. Execute the given line of code in that module’s context
4. Save state by looping through all variable bindings in the context and…
   • If the variable is hitherto unseen, store its name and value in the datastore
   • If not, ignore it. Here is the bug. You should actually check whether the variable has changed.