Re: [Tutor] Placing entire Application inside a class
"Jim Morcombe" <[EMAIL PROTECTED]> wrote > In it, Dakota recomends placing the entire application within a > class. > Why is this so? Surely in many cases you end up with a constructor > for the class that is cumbersome and complex? This is a very common OOP technique, especially in languages which only support objects, like Java and SmallTalk. Indeed some OOP purists would claim that its the only way to wsrite a pure OOP application. The constructor should not be very complex in a well constructed OOP program because it should only consist of processing any startup args and then the creation of a few top level objects. And without a top level class this would be done in some kind of initialisation function anyhow. Usually the App class will have a Run method or similar so that the module code looks like: module here class MyApp: def __init__(...) # process sys.argv # create top level classes as attributes def run(...) # control logic for application if __name__ == '__main__': MyApp().run() ### The advantage is that it is relatively easy to create variations of the program by subclassing the application. The disadvantage is that you don't often sub class applications in practice! (At least in my experience) > Is this a recomended Python programming technique? I've never seen it recommended for Python in general, but it is quite common, particularly in GUI apps. Indeed it is the recommend way for wxPython where you must create an Application class or use the built in SimpleApp class, HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Condensed python2.5 cheat sheet
Hi people, I've a competent programmer friend who I'm trying to convert to the ways of python and I was wondering if people could recommend a decent cheat sheet for python 2.5. He know how to program but just needs the syntax to become pythonic Thanks Andy ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Placing entire Application inside a class
Jim Morcombe wrote: > I have just read through "Creating a GUI in Python - by Dakota Lemaster" > > In it, Dakota recomends placing the entire application within a class. > > Why is this so? Surely in many cases you end up with a constructor for > the class that is cumbersome and complex? Many GUI frameworks (though not Tkinter) include an application class that you must instantiate and to start the application's event loop. It is convenient to subclass the framework's application class for your own initialization. Event callbacks for button presses, etc, generally must access some shared state, either the app's data model or other GUI elements or both. Shared state requires either global variables or a class instance to hold the state. Here again, an app class is useful. In my experience most apps don't have that many constructor arguments. If there are many options, usually some kind of settings object is created and used by the app. > Is this a recomended Python programming technique? For GUI programs it works well. For non-GUI programs classes may not be needed at all, it depends on the requirements of the program. One of the strengths of Python is that it allows different programming styles, you can pick the one that fits the problem and your preferences. > http://student-iat.ubalt.edu/sde/students/lemaster/COSC330/Final/sec4_AppClass.html In TicTacToe.py, notice that the event handler labelClicked() accesses self.labelList and self.gameOver. This is an example of shared state. The reset button is bound to a nested function; I think this would be better written as another method of the class also. Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Condensed python2.5 cheat sheet
Samm and Andy wrote: > Hi people, > > I've a competent programmer friend who I'm trying to convert to the ways > of python and I was wondering if people could recommend a decent cheat > sheet for python 2.5. > He know how to program but just needs the syntax to become pythonic Maybe one of these? http://rgruet.free.fr/ http://www.python.org/doc/QuickRef.html http://www.limsi.fr/Individu/pointal/python/pqrc/ Also Python in a Nutshell has a good, brief introduction to the language. Good luck! Kent ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Condensed python2.5 cheat sheet
There is an excellent book for programmers from other languages. Dive Into Python. http://www.diveintopython.org/toc/index.html Jeff On Wed, 2007-12-19 at 10:08 +, Samm and Andy wrote: > Hi people, > > I've a competent programmer friend who I'm trying to convert to the ways > of python and I was wondering if people could recommend a decent cheat > sheet for python 2.5. > He know how to program but just needs the syntax to become pythonic > > Thanks > > Andy > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Condensed python2.5 cheat sheet
"Samm and Andy" <[EMAIL PROTECTED]> wrote > of python and I was wondering if people could recommend a decent > cheat > sheet for python 2.5. There is a quick reference linked on the Python web site: Here is the URL: http://rgruet.free.fr/PQR25/PQR2.5.html However I'd still recommend an afternoon going through the official tutorial which introduces the idioms of Python aswell as the features and syntax. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.freenetpages.co.uk/hp/alan.gauld ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] Handling MySQLdb exceptions
Hi there!
I'm writing a script that inserts data from a .csv file into a
MySQL-Database.
Actually, it works fine (the data make it into the database correctly),
however everytime it runs it raises an exception coming from the
MySQLdb-module.
Here's the code:
--
#!/usr/bin/env python
import MySQLdb
import sys
if len(sys.argv) <> 2:
print("""Usage: put_data_into_pool
Columns need to be:
title, firstname, lastname, street, number of
house, postal code, city, phone number""")
sys.exit(0)
tabelle = open(sys.argv[1], "r")
db = MySQLdb.connect(host="localhost", user="user", passwd="",
db="db")
cursor = MySQLdb.cursors.Cursor(db)
line = tabelle.readline()
while line <> "":
#try:
cursor.execute('INSERT INTO pool (titel, vorname,
nachname, strasse, hausnummer, plz, ort, rufnummer, datum) VALUES (' +
line + ');')
line = tabelle.readline()
#except(_mysql_exceptions.OperationalError):
#pass
tabelle.close()
--
The exception goes like this:
--
Traceback (most recent call last):
File "bin/auftragserfassung/put_data_into_pool.py", line 22, in
cursor.execute('INSERT INTO pool (titel, vorname, nachname,
strasse, hausnummer, plz, ort, rufnummer, datum) VALUES (' + line + ');')
File "/var/lib/python-support/python2.5/MySQLdb/cursors.py", line
166, in execute
self.errorhandler(self, exc, value)
File "/var/lib/python-support/python2.5/MySQLdb/connections.py", line
35, in defaulterrorhandler
raise errorclass, errorvalue
_mysql_exceptions.OperationalError: (1136, "Column count doesn't match
value count at row 1")
---
Is there any way to handle this exception? As you can see, I already
tried it with _mysql_exceptions.OperationalError (the lines that are
commented out), but _mysql_exceptions is not defined to Python
Just so you don't need to wonder: The .csv-file I give to the script for
testing is absolutely OK.
On a side note, would you think I should post this somewhere else? If
so, where?
Any help is appreciated - I'll answer tomorrow (have to go now).
Kindest regards, Paul
___
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Re: [Tutor] Handling MySQLdb exceptions
On Dec 19, 2007 10:14 AM, Paul Schewietzek <[EMAIL PROTECTED]> wrote: > > Is there any way to handle this exception? As you can see, I already > tried it with _mysql_exceptions.OperationalError (the lines that are > commented out), but _mysql_exceptions is not defined to Python > > "OperationalError" is contained in the MySQLdb module and thus namespace, so you'll have to reference it like so: except MySQLdb.OperationalError: -- - http://stderr.ws/ "Insert pseudo-insightful quote here." - Some Guy ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Handling MySQLdb exceptions
Paul Schewietzek wrote: > Just so you don't need to wonder: The .csv-file I give to the script for > testing is absolutely OK. Except that it contains data that the insert statement doesn't like...does it contain any blank lines? Printing 'line' in the exception handler would be useful. Also this code is vulnerable to SQL injection attacks, if you don't trust the source of the input file you should not use this. For example if the file contained a line like titel, vorname, nachname, strasse, hausnummer, plz, ort, rufnummer,datum); delete from pool; -- that would be bad. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] constants, flags or whatever
In a program, I want to set some kind of variable or object to indicate what "mode" the program is currently in. What is the most elegant way of doing this? Jim --- constant: moving = "m" constant: inserting = "i" constant:jumping = "j" . . action = moving . . . if action == jumping: jumpSomewhere() elseif action == moving: moveSomewhere() elseif action == inserting: insertSomething() ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] constants, flags or whatever
This isn't elegant, but it is a start. My method is: get SOMETHING working, then work from there. 8^D """ constant: moving = "m" constant: inserting = "i" constant: jumping = "j" . . action = moving . . . if action == jumping: jumpSomewhere() elseif action == moving: moveSomewhere() elseif action == inserting: insertSomething() """ ## moving = False inserting = False jumping = False def jumpingSomewhere(): global jumping print jumping jumping = True return jumping def insertingSomething(): global inserting print inserting inserting = True return inserting def movingSomewhere(): global moving print moving moving = True return moving jumpingSomewhere() insertingSomething() movingSomewhere() print jumping print inserting print moving # Output: False False False True True True On Dec 19, 2007 8:44 PM, Jim Morcombe <[EMAIL PROTECTED]> wrote: > > > In a program, I want to set some kind of variable or object to indicate what > "mode" the program is currently in. > What is the most elegant way of doing this? > > Jim > --- > constant: moving = "m" > constant: inserting = "i" > constant:jumping = "j" > . > . > action = moving > . > . > . > if action == jumping: > jumpSomewhere() > elseif action == moving: > moveSomewhere() > elseif action == inserting: > insertSomething() > > > ___ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > -- b h a a l u u at g m a i l dot c o m ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] constants, flags or whatever
Jim Morcombe wrote: > In a program, I want to set some kind of variable or object to > indicate what "mode" the program is currently in. > What is the most elegant way of doing this? > > Jim > --- > constant: moving = "m" > constant: inserting = "i" > constant:jumping = "j" > . > . > action = moving > . > . > . > if action == jumping: > jumpSomewhere() > elseif action == moving: > moveSomewhere() > elseif action == inserting: > insertSomething() > 1 - I see no value in introducing variables. I'd just use string constants: action = "moving" . . if action == "jumping": etc. 2 - It is common in Python to use a dictionary to map the constants to the functions instead of if-elif statements: actions = dict( jumping = jumpSomewhere, moving = moveSomewhere, inserting = insertSomething) the entire if-elif construct now becomes: actions[action]() adding new action-function pairs is now a lot easier. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] constants, flags or whatever
On Wed, Dec 19, 2007 at 09:41:13PM -0500, bob gailer wrote: > 1 - I see no value in introducing variables. I'd just use string constants: > > action = "moving" > . > . > if action == "jumping": > > etc. I agree. But, some people do prefer something that looks a bit like an enum. If so, here is a Python idiom for enums: Mode_none, Mode_moving, Mode_inserting, Mode_jumping = range(4) action = Mode_moving if action == Mode_jumping: o o o - Dave -- Dave Kuhlman http://www.rexx.com/~dkuhlman ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] constants, flags or whatever
Dave Kuhlman wrote: > On Wed, Dec 19, 2007 at 09:41:13PM -0500, bob gailer wrote: > >> 1 - I see no value in introducing variables. I'd just use string constants: >> >> action = "moving" >> . >> . >> if action == "jumping": >> >> etc. > > I agree. But, some people do prefer something that looks a bit > like an enum. If so, here is a Python idiom for enums: One big advantage to using variables over string constants is that there is a big danger of misspelling one of the constants and not noticing the error. action = "moving" ... if action == "moveing": # oops, this never gets executed if you had used variables, Python would catch the error as an attempt to use an undefined variable: action = MOVING ... if action == MOVEING: <-- error caught by python > Mode_none, Mode_moving, Mode_inserting, Mode_jumping = range(4) > > action = Mode_moving > > if action == Mode_jumping: > o > o > o > > - Dave > > ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
