[Tutor] Help with cursors please
Hi, I have a SQLite cursor which I want to traverse more than once, eg... for row in MyCursor: method1(row) then later... for row in MyCursor: method2(row) Method2 is never run, I guess because the pointer is at the bottom of the row 'stack' after the first 'for' loop How can I move the pointer back to the top of the stack? Or do I have to reload the cursor first? Any help would be appreciated. Alan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Help with cursors please
Kent Johnson wrote: On Thu, Feb 4, 2010 at 12:47 PM, Alan Harris-Reid wrote: Hi, I have a SQLite cursor which I want to traverse more than once, eg... for row in MyCursor: method1(row) then later... for row in MyCursor: method2(row) Method2 is never run, I guess because the pointer is at the bottom of the row 'stack' after the first 'for' loop How can I move the pointer back to the top of the stack? Or do I have to reload the cursor first? Either reload the cursor or use fetchall() to get the results into a list and iterate the list. rows = MyCursor.fetchall() for row in rows; ... Kent Thanks for the reply Kent. I used fetchall() to get the results into a list and everything works fine now. Regards, Alan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] Superclass call problem
Hi, I am having trouble understanding how superclass calls work. Here's some code... class ParentClass(): def __init__(self): do something here class ChildClass(ParentClass): def __init__(self): super().__init__(self) # call parentclass __init__ method do something else here When the super().__init__ line runs I get the error "__init__() takes exactly 1 positional argument (2 given)" Can anyone tell me where I have gone wrong? I thought the self parameter should be passed to all class methods. TIA Alan Harris-Reid ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Superclass call problem
Kent Johnson wrote: On Sat, Feb 20, 2010 at 12:50 PM, Alan Harris-Reid wrote: Hi, I am having trouble understanding how superclass calls work. Here's some code... class ParentClass(): def __init__(self): do something here You should inherit object to use super(): class ParentClass(object): Kent Hi Kent, thanks for the reply, Sorry, left out 'object' from my example. The actual code already reads class ParentClass(object): Alan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Superclass call problem
Luke Paireepinart wrote: Your call to super is wrong. It should be super and you pass the class and instance, then call init. On 2/20/10, Alan Harris-Reid wrote: Hi, I am having trouble understanding how superclass calls work. Here's some code... class ParentClass(): def __init__(self): do something here class ChildClass(ParentClass): def __init__(self): super().__init__(self) # call parentclass __init__ method do something else here When the super().__init__ line runs I get the error "__init__() takes exactly 1 positional argument (2 given)" Can anyone tell me where I have gone wrong? I thought the self parameter should be passed to all class methods. TIA Alan Harris-Reid ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor Hi Luke, thanks for the reply, In addition to your suggestion, looks like I can use class ChildClass(ParentClass): def __init__(self, arg): super(ParentClass, self).__init__(arg) or super().__init__(arg)# this only works in Python 3, I think I prefer the 2nd way, as it is more generic (ie. don't need to state parent-class). Regards, Alan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Superclass call problem
Hi, I am having trouble understanding how superclass calls work. Here's some code... What version of Python are you using? In Python 2.x, you MUST inherit from object to use super, and you MUST explicitly pass the class and self: class ParentClass(object): def __init__(self, a, b, c): do something here class ChildClass(ParentClass): def __init__(self, a, b, c): super(ChildClass, self).__init__(a, b, c) In Python 3.x, all classes inherit from object and you no longer need to explicitly say so, and super becomes a bit smarter about where it is called from: # Python 3 only class ParentClass: def __init__(self, a, b, c): do something here class ChildClass(ParentClass): def __init__(self, a, b, c): super().__init__(a, b, c) I assume you are using Python 3.0 or 3.1. (If you're 3.0, you should upgrade to 3.1: 3.0 is s-l-o-w and no longer supported.) Your mistake was to pass self as an explicit argument to __init__. This is not needed, because Python methods automatically get passed self: def __init__(self): super().__init__(self) That has the effect of passing self *twice*, when __init__ expects to get self *once*, hence the error message you see: When the super().__init__ line runs I get the error "__init__() takes exactly 1 positional argument (2 given)" Hi Steven, thanks for the reply. Fortunately I am using Python 3.1, so I can use the super().__init__(a, b, c) syntax. Regards, Alan ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] SQLite error messages
Hi there,
I am using the sqlite3 module with Python 3.1, and have some code which
goes something like as follows...
import sqlite3
con = sqlite3.connect('MyDatabase.db')
try:
execresult = con.execute('INSERT INTO MyTable (field_name) VALUES
("MyValue")')
con.commit()
except:
con.rollback()
If con.execute() fails, nothing is returned, and although the code
correctly executes the rollback next, I have no idea why, and therefore
cannot create a suitable error-handler with meaningful messages.
I notice from the SQLite website that there are error codes, but it
looks like the sqlite3 module is not reporting them.
Has anyone any ideas how to get around this problem?
TIA,
Alan Harris-Reid
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Re: [Tutor] SQLite error messages
Benno Lang wrote:
On 10 March 2010 11:37, Alan Harris-Reid wrote:
Hi there,
I am using the sqlite3 module with Python 3.1, and have some code which goes
something like as follows...
import sqlite3
con = sqlite3.connect('MyDatabase.db')
try:
execresult = con.execute('INSERT INTO MyTable (field_name) VALUES
("MyValue")')
con.commit()
except:
con.rollback()
If con.execute() fails, nothing is returned, and although the code
correctly executes the rollback next, I have no idea why, and therefore
cannot create a suitable error-handler with meaningful messages.
I notice from the SQLite website that there are error codes, but it looks
like the sqlite3 module is not reporting them.
Do you mean numerical error codes? Which page on the SQLite website
are you referring to? Certainly the exception contains usable data.
Try something like this:
try:
execresult = con.execute('INSERT INTO MyTable (field_name) VALUES
("MyValue")')
con.commit()
except Exception as error:
print("Didn't work:", error)
con.rollback()
(I didn't create a table, so I get "Didn't work: no such table: MyTable")
HTH,
benno
Hi Benno, your example is great - just what I needed!
Regarding SQLite error codes, the list I was referring to is at
www.sqlite.org/c3ref/c_abort.html
<http://www.sqlite.org/c3ref/c_abort.html>, but it doesn't look complete
because I have already come-across some IntegrityError messages which
aren't on the list.
Regards,
Alan
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Re: [Tutor] SQLite error messages
Sander Sweers wrote:
- Original message -
I am using the sqlite3 module with Python 3.1, and have some code which
goes something like as follows...
import sqlite3
con = sqlite3.connect('MyDatabase.db')
try:
execresult = con.execute('INSERT INTO MyTable (field_name) VALUES
("MyValue")')
con.commit()
except:
Here you catch all exceptions. Normally you would catch a specific exception like ValueError.
con.rollback()
Do you know finally? It is run after all the exceptions have been handled and
this is where I would put the rollback.
Greets,
Sander
Hello Sander, thanks for the reply.
"Normally you would catch a specific exception like ValueError."
Agreed, but as I don't know what type the exception is, I would have to
provide a suitable error message for all exception types (ValueError,
IntegrityError, etc.). At this stage catching Exception as errormessage
is sufficient for my purposes.
"Do you know finally? It is run after all the exceptions have been
handled and this is where I would put the rollback."
In this case there is no 'finally' section, because if the 'try' section
doesn't work, then I want the rollback to occur for *all *exceptions.
Maybe I have misunderstood you, but I always thought that the 'finally'
section was run even if the 'try' section is successful, in which case I
would not want a rollback. (According to the Python documentation
(section 8.6) "A /finally clause/ is always executed before leaving the
try
statement, whether an exception has occurred or not.").
Regards,
Alan
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Re: [Tutor] Unable to run a simple Hello.py in WinXP
Hi Siva, I can run the .py file from the DOS command line without any problem under WinXP. Can you give some more information regarding your error message? Regards, Alan Harris-Reid ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Cherrypy and Iframes (or how to insert a file in a, page)
Andreas... > NotFound: (404, "The path '/file.txt' was not found.") This error message often occurs because file.txt is a static file and you have not told CherryPy where to look for static files. From the look of the error I am guessing that file.txt is in your root directory, in which case you need the following in your configuration file. [/] tools.staticdir.root = '/path/to/root/folder' # no trailing backslash tools.staticdir.on = True tools.staticdir.dir = "" # necessary to serve static files in home folder Hope this helps. Alan Harris-Reid ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
