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Python takes some getting used to.  The clean syntax is great, but it has some things which a Java or Ruby programmer might not guess.  

== Problem with deadline after upgrade ==

When starting python you get an IO error:
<geshi lang="bash">
$ python
Python 2.6.7 (r267:88850, Feb  3 2012, 20:21:47) 
[GCC 4.2.1 Compatible Apple Clang 3.0 (tags/Apple/clang-211.12)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
/Users/brianegge/.pyhistory
Traceback (most recent call last):
  File "/Users/brianegge/.pystartup", line 24, in <module>
    readline.read_history_file(historyPath)
IOError: [Errno 2] No such file or directory
>>>
</geshi>

Your ~/.pystartup looks like:
<geshi lang="python">
import atexit
import os
import readline
import rlcompleter

historyPath = os.path.expanduser("~/.pyhistory")

def save_history(historyPath=historyPath):
    import readline
    readline.write_history_file(historyPath)

if os.path.exists(historyPath):
    readline.read_history_file(historyPath)
</geshi>

The solution is to remove your old history file '''rm /Users/brianegge/.pyhistory'''

After you run python again, you will see new magic at the top of your readline file:
<geshi lang="bash">
cat ~/.pyhistory
_HiStOrY_V2_
</geshi>

== How to tell if an object is None ==

This won't parse:
<geshi lang="python">
user = users.get_current_user()
if !user:
    gologin()
</geshi>

This works:
<geshi lang="python">
if not bool(user):
    gologin()
</geshi>

As does:
<geshi lang="python">
if user == None:
    gologin()
</geshi>

But this is probably best:
<geshi lang="python">
if user is None:
    gologin()
</geshi>

This article "[http://mail.python.org/pipermail/python-list/2003-March/192769.html what exactly is "None"]" helped explain this a little better.

[[Category:Python]]