Re: [Tutor] best approach to db-api imports and cursor calls
"Serdar Tumgoren" wrote Is there any reason why you can't reuse the same cursor object? I know when you're writing to a database, you have to be sure to commit your changes. But if I'm just issuing execute statements and then fetching data, is it okay to reuse the same cursor? No, there is no reason. You can reuse a single cursor as often as you like provided you are happy to take responsibility for keeping the transactions clean - eg not trying to read data from one while writing at the same time, or combining two different selects, and committing between each change transaction. But most folks find multiple cursors easier to manage in the same way that they find multiple variables easier than reusing a minimal number. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] To write data in two different fonts?
Nick Raptis wrote:
Dave
Angel wrote:
As I said, you'd probably get in trouble if any of the lines had '&'
or '<' characters in them. The following function from the standard
library can be used to escape the line directly, or of course you
could use the function Nick supplied.
xml.sax.saxutils.escape(/data/[, /entities/])
Escape '&', '<', and '>' in a string of data.
You can escape other strings of data by passing a dictionary as the
optional /entities/ parameter. The keys and values must all be
strings; each key will be replaced with its corresponding value. The
characters '&', '<' and '>' are always escaped, even if /entities/
is provided.
Let us know if that doesn't do the trick.
DaveA
Thanks Dave for the info on xml.sax.saxutils.escape
Didn't know about this one.
For the rest:
It is sometimes
This is the source code of the xml.sax.saxutils.escape function:
---
def __dict_replace(s, d):
"""Replace substrings of a string using a dictionary."""
for key, value in d.items():
s = s.replace(key, value)
return s
def escape(data, entities={}):
"""Escape &, <, and > in a string of data.
You can escape other strings of data by passing a dictionary as
the optional entities parameter. The keys and values must all be
strings; each key will be replaced with its corresponding value.
"""
# must do ampersand first
data = data.replace("&", "&")
data = data.replace(">", ">")
data = data.replace("<", "<")
if entities:
data = __dict_replace(data, entities)
return data
-
As you can see, it too uses string.replace to do the job.
However, using a built-in function that works for what you want to do
is preferable.
It's tested and might also be optimized to be faster.
It's easy and fun to look into the source though and know exactly what
something does.
It's also one of the ways for a begginer (me too) to progress.
From the source code I can see this for example:
*Don' t pass the entity dictionary I proposed earlier to this function:*
entities = {'&' : '&',
'<' : '<',
'>' : '>',
'"' : '"',
"'" : '''}
If you pass an entity for '&' into escape(), it will escape it in the
already partially escaped string, resulting in chaos.
Think of it, this function not checking for a '&' entity passed to it
might worth qualifying as a bug :)
Nick
Yes, duplicating the & entitity would be a bug in the caller's code
in this case. (see my posted improvements to the OP code, which removed
the variable entities entirely) The question is whether this function's
doc should have such a warning, or whether the function should make sure
double-substitution does not happen.
The & entity is the only predefined entity in the S3 standard that
has this problem. For example, there's no entity that replaces the
letter 'a' or the semicolon. And a quote sign is never used within an
encoded entity.
I think perhaps an improved version would either ignore a & key in the
supplied dictionary, or throw an exception if one is encountered. The
question that must always be answered is whether this could break
existing code.
There are legitimate reasons for a string to be escaped twice. Think
what happens when a website wants to quote some html source code. Or a
little less recursively, suppose you have a website teaching xml. The
examples posted would need to be double-escaped. However, if someone
had tried to do that in a single call to the current function, their
code would already be broken because the dictionary doesn't preserve
order, so the & substitution might not happen first. Such a user must
call the escape function twice, without passing & at all.
DaveA
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Re: [Tutor] best approach to db-api imports and cursor calls
> But most folks find multiple cursors easier to manage in the same way that > they find multiple variables easier than reusing a minimal number. > That makes sense. I think I'll try using a global import/connect, and then create cursors inside each method. Thanks to you both for the advice! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] best approach to db-api imports and cursor calls
Serdar Tumgoren wrote: But most folks find multiple cursors easier to manage in the same way that they find multiple variables easier than reusing a minimal number. That makes sense. I think I'll try using a global import/connect, and then create cursors inside each method. Thanks to you both for the advice! ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor You can also pass the connection object around from your __main__ so you can call .commit() and .rollback() when you need without polluting globals. -- Kind Regards, Christian Witts ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] To write data in two different fonts?
Dave Angel wrote: However, if someone had tried to do that in a single call to the current function, their code would already be broken because the dictionary doesn't preserve order, so the & substitution might not happen first. Wow, I never thought about the dictionary not being sorted messing things up. Thanks for the insight. Nick ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Web framework: looking for python-tutor's angle.
A couple of months ago I took the time to read a few articles on python web application frameworks and I got the impression that the two most mature and active projects are Zope and Django. Zope vs. Django hits 879.000 pages on google but much of the debate - or at least this is my impression - falls into the class "vi vs. emacs" or "gtk vs. qt" with many people singling out a single characteristics that for them is THE characteristic making one framework better than the other. This [1] graph seems to corroborate my final impression (i.e. that django is the way to go). Yet, I would be very interested in hearing what the members of this list think, as I particularly enjoy the "learner centered" approach that most of the people seems to have here. I believe my needs are quite ordinary: my customers are typically small businesses needing to process their data on a single server, sometime exposing part of the application as front-end to the customers (hence easy and flexible theming is important). I would definitively be happy to sacrifice some functionality in exchange for a leaner and cleaner design (i.e. more modular, elegant and intuitive), though. Thank you in advance for your time, Mac. [1] http://www.google.com/trends?q=python+zope%2C+python+django ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Web framework: looking for python-tutor's angle.
On Thu, Aug 13, 2009 at 2:09 PM, Mac Ryan wrote: > A couple of months ago I took the time to read a few articles on python > web application frameworks and I got the impression that the two most > mature and active projects are Zope and Django. > > Zope vs. Django hits 879.000 pages on google but much of the debate - or > at least this is my impression - falls into the class "vi vs. emacs" or > "gtk vs. qt" with many people singling out a single characteristics that > for them is THE characteristic making one framework better than the > other. > I have worked with both Zope and Django. When I worked with Zope, it had a lot of powerful features like their version of interfaces and zodb (zope object database - think of a high performance dictionary) but the learning curve was very high. After a couple of weeks of messing with it, my partner and I drop it for Django. Django allows you to get up and doing productive work in a couple of hours instead of a couple of days or weeks. If you are under any time constraints and do not have experience with either one, go with Django. -Tino ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Web framework: looking for python-tutor's angle.
I've never used Zope so I can't speak to its strengths or weaknesses. But I can say that Django is quite natural if you already know Python. It certainly is modular, with a ton of apps that you can plug in to gain added functionality. And there's also a project called Pinax that provides layers of CMS-type functionality (e.g. authentication, blogging, wiki, etc.) that can save you from reinventing the wheel. Here are a few places to explore: http://djangoplugables.com/ http://pinaxproject.com/ Search Google Code for django HTH, Serdar ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Dynamic Function Calls
Hi,
I'm trying to call a function from a dictionary. I did some googling and
from what I can tell my code should work, but doesn't. Here's an example:
def myFunc(self, inputList):
dict={0: func0, 1: func1, 2:func2}
for element in inputList:
dict[element]()
When I go to run this I get an error saying func0 is not defined. Does
anyone have any ideas as to why this won't work? I'm using Python 2.6 if
that makes any difference.
Thanks!
Megan Land
FVT Blade EMET Test Engineer
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Re: [Tutor] Dynamic Function Calls
On Thu, Aug 13, 2009 at 3:30 PM, Megan Land wrote:
> Hi,
>
> I'm trying to call a function from a dictionary. I did some googling and
> from what I can tell my code should work, but doesn't. Here's an example:
>
> def myFunc(self, inputList):
> dict={0: func0, 1: func1, 2:func2}
> for element in inputList:
> dict[element]()
>
> When I go to run this I get an error saying func0 is not defined. Does
> anyone have any ideas as to why this won't work? I'm using Python 2.6 if
> that makes any difference.
You don't show any definition for func0 in the above snippet. Where is
it defined?
Kent
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Re: [Tutor] Dynamic Function Calls
"Megan Land" wrote
I'm trying to call a function from a dictionary. I did some googling and
from what I can tell my code should work, but doesn't. Here's an
example:
def myFunc(self, inputList):
The fact you have a self in there suggests that this is a method
of some class? Is it? If not remove the self.
dict={0: func0, 1: func1, 2:func2}
What do you think this is doing? What are func0, func1 etc?
Where are they defined?
for element in inputList:
dict[element]()
This will work provided element exists in dict and dict[element]
is a callable object, eg a function. But I recommend putting
some error handling in for the cases where either of those
two conditions is not true
When I go to run this I get an error saying func0 is not defined. Does
anyone have any ideas as to why this won't work?
Because you haven't defined func0!
try adding
def func0(): print 'func0'
def func1(): print 'func1'
def func2(): print 'func2'
above your function.
Then it might work if you call you function like this:
myFunc([func2,func0,func1])
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] Web framework: looking for python-tutor's angle.
"Mac Ryan" wrote A couple of months ago I took the time to read a few articles on python web application frameworks and I got the impression that the two most mature and active projects are Zope and Django. They are both mature and widely used, but for quite different markets. TurboGears is a more direct competitor to Django and there is no competitor (in the Python world) to Zope This [1] graph seems to corroborate my final impression (i.e. that django is the way to go). I believe my needs are quite ordinary: my customers are typically small businesses needing to process their data on a single server, sometime exposing part of the application as front-end to the customers That sounds like Django to me. Zope is better suited to large scale corporate type scenarios with high volumes. If Zope can't cope you really need to move to the big guns like BEA Weblogic etc.. But for SMEs Django (et al) is ideal. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
