Re: [Tutor] why do i get None as output
On Mon, Sep 6, 2010 at 8:34 AM, Roelof Wobben wrote:
> Hello,
>
> I have this programm:
>
> def encapsulate(val, seq):
> if type(seq) == type(""):
> return str(val)
> if type(seq) == type([]):
> return [val]
> return (val,)
>
> def insert_in_middle(val, seq):
> middle = len(seq)/2
> return seq[:middle] + encapsulate(val, seq) + seq[middle:]
>
> def make_empty(seq):
> """
> >>> make_empty([1, 2, 3, 4])
> []
> >>> make_empty(('a', 'b', 'c'))
> ()
> >>> make_empty("No, not me!")
> ''
> """
> word2=""
> teller=0
> if type(seq) == type([]):
> teller=0
> while teller < len(seq):
> seq[teller]=""
> teller = teller + 1
> elif type(seq) == type(()):
> tup2 = list (seq)
> while teller > tup2.len():
> tup2[teller]=""
> teller = teller + 1
> seq = tuple(tup2)
> else:
> seq = ""
>
> test = make_empty([1, 2, 3, 4])
> print test
>
> But now I get None as output instead of []
>
> Can anyone explain why that happens ?
test = make_empty([1, 2, 3, 4]) makes test equal to the return value
of make_empty. But make_empty does not return anything, and in that
case its return value is made equal to empty. Compare:
def f(x):
x = x + 1
def g(x):
x = x + 1
return x
def h(x):
return x +1
print f(1)
>> None
print g(1)
>> 2
print h(1)
>> 2
--
André Engels, andreeng...@gmail.com
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] why do i get None as output
"Roelof Wobben" wrote def make_empty(seq): word2="" teller=0 if type(seq) == type([]): teller=0 while teller < len(seq): seq[teller]="" teller = teller + 1 elif type(seq) == type(()): tup2 = list (seq) while teller > tup2.len(): tup2[teller]="" teller = teller + 1 seq = tuple(tup2) else: seq = "" test = make_empty([1, 2, 3, 4]) But now I get None as output instead of [] Because None is the default return value from a function. If you do not return a value (which you don;t in this case) then Python automatically returns None. You need to return something from your make_empty function. Also, if all you want to do is return an empty version of whatever has been passed in there are much easier ways of doing it! And in fact, a list of empty strings is not the same as an empty list... HTH -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] setattr vs __setattr__
Hi all, Suppose we have class A(object): pass a = A() Is there any difference between setattr(a, 'foo', 'bar) and a.__setattr__['foo'] = 'bar' other than syntax? And which is considered 'better' form in Python? Cheers, Rasjid. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] why do i get None as output
> To: tutor@python.org
> From: alan.ga...@btinternet.com
> Date: Mon, 6 Sep 2010 08:27:31 +0100
> Subject: Re: [Tutor] why do i get None as output
>
>
> "Roelof Wobben" wrote
>
> def make_empty(seq):
> word2=""
> teller=0
> if type(seq) == type([]):
> teller=0
> while teller < len(seq):
> seq[teller]=""
> teller = teller + 1
> elif type(seq) == type(()):
> tup2 = list (seq)
> while teller > tup2.len():
> tup2[teller]=""
> teller = teller + 1
> seq = tuple(tup2)
> else:
> seq = ""
>
> test = make_empty([1, 2, 3, 4])
>
> But now I get None as output instead of []
>
>
> Because None is the default return value from a function.
> If you do not return a value (which you don;t in this case) then
> Python automatically returns None.
>
> You need to return something from your make_empty function.
>
> Also, if all you want to do is return an empty version of
> whatever has been passed in there are much easier
> ways of doing it! And in fact, a list of empty strings is
> not the same as an empty list...
>
>
> HTH
>
> --
> Alan Gauld
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
>
>
> ___
> Tutor maillist - Tutor@python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor
Oke,
I put a return seq in the programm and it looks now like this :
def encapsulate(val, seq):
if type(seq) == type(""):
return str(val)
if type(seq) == type([]):
return [val]
return (val,)
def insert_in_middle(val, seq):
middle = len(seq)/2
return seq[:middle] + encapsulate(val, seq) + seq[middle:]
def make_empty(seq):
"""
>>> make_empty([1, 2, 3, 4])
[]
>>> make_empty(('a', 'b', 'c'))
()
>>> make_empty("No, not me!")
''
"""
if type(seq) == type([]):
seq = []
elif type(seq) == type(()):
seq=()
else:
seq = ""
return seq
if __name__ == "__main__":
import doctest
doctest.testmod()
This works but I don't think its what the exercise means :
Create a module named seqtools.py. Add the functions encapsulate and
insert_in_middle from the chapter. Add doctests which test that these two
functions work as intended with all three sequence types.
Add each of the following functions to seqtools.py:
def make_empty(seq):
"""
>>> make_empty([1, 2, 3, 4])
[]
>>> make_empty(('a', 'b', 'c'))
()
>>> make_empty("No, not me!")
''
"""
So i think I have to use encapsulate and insert_in_middle. And I don't use it.
Roelof
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] why do i get None as output
On Mon, Sep 6, 2010 at 9:41 AM, Roelof Wobben wrote:
>
>
>> To: tutor@python.org
>> From: alan.ga...@btinternet.com
>> Date: Mon, 6 Sep 2010 08:27:31 +0100
>> Subject: Re: [Tutor] why do i get None as output
>>
>>
>> "Roelof Wobben" wrote
>>
>> def make_empty(seq):
>> word2=""
>> teller=0
>> if type(seq) == type([]):
>> teller=0
>> while teller < len(seq):
>> seq[teller]=""
>> teller = teller + 1
>> elif type(seq) == type(()):
>> tup2 = list (seq)
>> while teller > tup2.len():
>> tup2[teller]=""
>> teller = teller + 1
>> seq = tuple(tup2)
>> else:
>> seq = ""
>>
>> test = make_empty([1, 2, 3, 4])
>>
>> But now I get None as output instead of []
>>
>>
>> Because None is the default return value from a function.
>> If you do not return a value (which you don;t in this case) then
>> Python automatically returns None.
>>
>> You need to return something from your make_empty function.
>>
>> Also, if all you want to do is return an empty version of
>> whatever has been passed in there are much easier
>> ways of doing it! And in fact, a list of empty strings is
>> not the same as an empty list...
>>
>>
>> HTH
>>
>> --
>> Alan Gauld
>> Author of the Learn to Program web site
>> http://www.alan-g.me.uk/
>>
>>
>> ___
>> Tutor maillist - Tutor@python.org
>> To unsubscribe or change subscription options:
>> http://mail.python.org/mailman/listinfo/tutor
>
> Oke,
>
> I put a return seq in the programm and it looks now like this :
>
> def encapsulate(val, seq):
> if type(seq) == type(""):
> return str(val)
> if type(seq) == type([]):
> return [val]
> return (val,)
>
> def insert_in_middle(val, seq):
> middle = len(seq)/2
> return seq[:middle] + encapsulate(val, seq) + seq[middle:]
>
> def make_empty(seq):
> """
> >>> make_empty([1, 2, 3, 4])
> []
> >>> make_empty(('a', 'b', 'c'))
> ()
> >>> make_empty("No, not me!")
> ''
> """
> if type(seq) == type([]):
> seq = []
> elif type(seq) == type(()):
> seq=()
> else:
> seq = ""
> return seq
>
> if __name__ == "__main__":
> import doctest
> doctest.testmod()
>
> This works but I don't think its what the exercise means :
>
>
> Create a module named seqtools.py. Add the functions encapsulate and
> insert_in_middle from the chapter. Add doctests which test that these two
> functions work as intended with all three sequence types.
>
> Add each of the following functions to seqtools.py:
>
> def make_empty(seq):
> """
> >>> make_empty([1, 2, 3, 4])
> []
> >>> make_empty(('a', 'b', 'c'))
> ()
> >>> make_empty("No, not me!")
> ''
> """
>
> So i think I have to use encapsulate and insert_in_middle. And I don't use
> it.
I don't think so. They don't look like the kind of thing that would be
useful for this function. In your example seqtools.py is supposed to
be a (toy example of a) library, a collection of functions to do
things with sequence-like objects to be used by other programs. These
functions in general need not have much to do with eachother, except
that they work on the same type of objects.
--
André Engels, andreeng...@gmail.com
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] setattr vs __setattr__
On Mon, Sep 6, 2010 at 9:27 AM, Rasjid Wilcox wrote:
> Hi all,
>
> Suppose we have
>
> class A(object):
> pass
>
> a = A()
>
> Is there any difference between
>
> setattr(a, 'foo', 'bar)
>
> and
>
> a.__setattr__['foo'] = 'bar'
>
Did you mean a.__setattr__('foo', 'bar')? That's the same thing,
though you'd generally use a.foo = 'bar' or setattr(a, 'foo', 'bar'),
in that order of preference.
If you meant a.__dict__['foo'] = 'bar', that may or may not be the
same thing depending on the class. It works for instances of object,
but fails for any class that defines __slots__, for example. I'd
generally recommend you don't do it. Use setattr instead.
Hugo
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] setattr vs __setattr__
On 6 September 2010 19:55, Hugo Arts wrote:
> On Mon, Sep 6, 2010 at 9:27 AM, Rasjid Wilcox wrote:
>> Hi all,
>>
>> Suppose we have
>>
>> class A(object):
>> pass
>>
>> a = A()
>>
>> Is there any difference between
>>
>> setattr(a, 'foo', 'bar)
>>
>> and
>>
>> a.__setattr__['foo'] = 'bar'
>>
>
> Did you mean a.__setattr__('foo', 'bar')? That's the same thing,
> though you'd generally use a.foo = 'bar' or setattr(a, 'foo', 'bar'),
> in that order of preference.
Sorry, yes, a.__setattr__('foo', 'bar') is what I meant. I'm actually
iterating over a number of attributes, so AFASK the first form is not
an option. I've been using
for attr_name in name_list:
setattr(a, attr_name, getattr(b, attr_name))
to copy the attributes from one type of class to another, and it is
not quite as readable as I would like. Actually, I've just thought
that the best option would be to make both classes dictionary like
objects with automatic translation between a['foo'] and a.foo.
Sqlalchemy uses that for its query result objects with good effect.
Cheers,
Rasjid.
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
[Tutor] Arguments from the command line
I've seen Python programs that can be activated from the command line. For example: hg This displays a list of commands for the Mercurial revision control system. But another command is this: hg commit "This is a commit name" Mercurial is written in Python. I know that commit is a function that commits to a repo, but what command does the program use in order to get the commit name, like "This is a commit name" (This would make a commit with "This is a commit name" as the commit name) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Arguments from the command line
On Mon, Sep 6, 2010 at 5:48 PM, aug dawg wrote: > I've seen Python programs that can be activated from the command line. For > example: > hg > > This displays a list of commands for the Mercurial revision control system. > But another command is this: > hg commit "This is a commit name" > Mercurial is written in Python. I know that commit is a function that > commits to a repo, but what command does the program use in order to get the > commit name, like "This is a commit name" (This would make a commit with > "This is a commit name" as the commit name) > sys.argv is a list of all arguments from the command line. However, you'll rarely deal with it directly, there's various modules that deal with handling arguments. I believe the current one is argparse: http://docs.python.org/library/argparse.html#module-argparse Hugo ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Arguments from the command line
I think you're looking for this: http://docs.python.org/library/argparse.html you'll also want to read up on sys.argv http://docs.python.org/library/sys.html#sys.argv On Mon, Sep 6, 2010 at 8:48 AM, aug dawg wrote: > I've seen Python programs that can be activated from the command line. For > example: > > hg > > This displays a list of commands for the Mercurial revision control system. > But another command is this: > > hg commit "This is a commit name" > > Mercurial is written in Python. I know that commit is a function that > commits to a repo, but what command does the program use in order to get the > commit name, like "This is a commit name" (This would make a commit with > "This is a commit name" as the commit name) > > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Arguments from the command line
On 9/6/2010 11:48 AM, aug dawg wrote: I've seen Python programs that can be activated from the command line. For example: hg This displays a list of commands for the Mercurial revision control system. But another command is this: hg commit "This is a commit name" Mercurial is written in Python. I know that commit is a function that commits to a repo, but what command does the program use in order to get the commit name, like "This is a commit name" (This would make a commit with "This is a commit name" as the commit name) hg.py: import sys print sys.argv $hg commit "This is a commit name" ['C:\\hg.py', 'commit', 'This is a commit name'] -- Bob Gailer 919-636-4239 Chapel Hill NC ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] exercise correct ??
Hello,
I have this programm :
def index_of(val, seq, start=0):
"""
>>> index_of(9, [1, 7, 11, 9, 10])
3
>>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5))
3
>>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
6
>>> index_of('y', 'happy birthday')
4
>>> index_of('banana', ['apple', 'banana', 'cherry', 'date'])
1
>>> index_of(5, [2, 3, 4])
-1
>>> index_of('b', ['apple', 'banana', 'cherry', 'date'])
-1
"""
plek = 0
if type(seq) == type([]):
plek = seq.index(val)
elif type(seq) == type(()):
seq = list (seq)
plek = seq.index(val)
else :
plek = seq.find(val)
return plek
But I get this message :
File "C:\Users\wobben\workspace\oefeningen\src\test.py", line 70, in
__main__.index_of
Failed example:
index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
Expected:
6
Got:
3
But in that tuple 5 is on position 3.
Is the exercise here wrong ?
Roelof
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
[Tutor] Simple Python Problem
What is wrong with the following, apparently almost straight out of Python
Programming
by Michael Dawson?
# Declare variable and initialise (overkill!).
name = "ABCDEFG"
# Get value.
name = input("What is your name? ")
# Echo value
print(name)
# Issue greeting
print("Hi ", name)
Python 2.7 (r27:82525, Jul 4 2010, 09:01:59) [MSC v.1500 32 bit (Intel)] on
win32 Type
"copyright", "credits" or "license()" for more information.
>>> RESTART
What is your name? Keith
Traceback (most recent call last):
File "C:\Documents and Settings\User\My Documents\My Files\Staff\Keith
Lucas\Education\Python\Learn_Input_01.py", line 5, in
name = input("What is your name? ")
File "", line 1, in
NameError: name 'Keith' is not defined
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
[Tutor] Multiple versions of python and paths problems
Hello,
I usually use python 2.6 and several packages. Everything's fine.
At present, I'm trying to run a package which is only available with python 2.5.
So, i installed 2.5 and the various dependencies needed to run this package:
PIL, numpy... which were already installed in my 2.6 site-packages.
Unfortunately, when I try to run it under Idle 2.5, python goes in the 2.6
site-packages to get these dependencies (PIL,...) and throws me a traceback (due
to incompatibilities).
I understand it is a paths problem.
So, I added the path of python 2.5 and that of my application to the path and
Pythonpath in the windows environ variables.
But the same problems arise.
So, I tried to load the normal 2.5 Idle and unload ('remove') everything related
to 2.6 from sys.path, but it's strangely not working completely.
Finally, I managed to run the program :
- by launching D:\python25\python.exe -E -S in a console (which seems to prevent
python from loading the paths)
- then appending the application path to sys.path
but it's really not fun working with this bloody windows console where cut and
paste is impossible...
So, here is my question:
How can I force py2.5 to go and find the dependencies only in the 2.5
site-packages ?
Thanks in advance for your help.
Dominique
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Simple Python Problem
"Keith Lucas" wrote
What is wrong with the following, apparently almost straight out of
Python Programming
by Michael Dawson?
You are using Python v2, the tutorial seems to be written for v3.
There are big diffeernces in syntax between them, v3 is NOT
backwards compatible with v2.
# Get value.
name = input("What is your name? ")
In v2 that would be
name = raw_input("What is your name")
Python 2.7 (r27:82525, Jul 4 2010, 09:01:59) [MSC v.1500 32 bit
(Intel)] on win32 Type
"copyright", "credits" or "license()" for more information.
RESTART
What is your name? Keith
I think there is a trick in V2.7 to make it act more like v3 but
someone
else will need to tell you what it is... :-)
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] why do i get None as output
On 06/09/2010 8.34, Roelof Wobben wrote:
Hello,
I have this programm:
...
def make_empty(seq):
"""
>>> make_empty([1, 2, 3, 4])
[]
>>> make_empty(('a', 'b', 'c'))
()
>>> make_empty("No, not me!")
''
"""
word2=""
teller=0
if type(seq) == type([]):
teller=0
while teller < len(seq):
seq[teller]=""
teller = teller + 1
elif type(seq) == type(()):
tup2 = list (seq)
while teller > tup2.len():
tup2[teller]=""
teller = teller + 1
seq = tuple(tup2)
else:
seq = ""
test = make_empty([1, 2, 3, 4])
print test
But now I get None as output instead of []
I would add a line like:
return seq
at the end of the make_empty function.
Can anyone explain why that happens ?
I think Python doesn't know what exactly is the value you need to
receive from the make_empty function. That's why I'd make it clear.
Otherwise, you know what happens...
I quote the following from
http://diveintopython.org/getting_to_know_python/declaring_functions.html
"In fact, every Python function returns a value; if the function ever
executes a return statement, it will return that value, otherwise it
will return None, the Python null value."
Roelof
Francesco
Nessun virus nel messaggio in uscita.
Controllato da AVG - www.avg.com
Versione: 9.0.851 / Database dei virus: 271.1.1/3115 - Data di rilascio:
09/05/10 08:34:00
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Simple Python Problem
> > > Python 2.7 (r27:82525, Jul 4 2010, 09:01:59) [MSC v.1500 32 bit (Intel)] >> on win32 Type >> "copyright", "credits" or "license()" for more information. >> >>> RESTART > What is your name? Keith >> > > I think there is a trick in V2.7 to make it act more like v3 but someone > else will need to tell you what it is... :-) > > Other than changing the input() to raw_input() for Python 2 compatibility, the following statement could be added to the beginning of the program to allow your Python 2 program to use the Python 3 style print function. from __future__ import print_function -Bill ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Multiple versions of python and paths problems
On Mon, Sep 6, 2010 at 1:46 PM, Dominique wrote:
> Hello,
>
> I usually use python 2.6 and several packages. Everything's fine.
>
> At present, I'm trying to run a package which is only available with python
> 2.5.
> So, i installed 2.5 and the various dependencies needed to run this package:
> PIL, numpy... which were already installed in my 2.6 site-packages.
>
> Unfortunately, when I try to run it under Idle 2.5, python goes in the 2.6
> site-packages to get these dependencies (PIL,...) and throws me a traceback
> (due
> to incompatibilities).
>
> I understand it is a paths problem.
>
> So, I added the path of python 2.5 and that of my application to the path and
> Pythonpath in the windows environ variables.
> But the same problems arise.
>
> So, I tried to load the normal 2.5 Idle and unload ('remove') everything
> related
> to 2.6 from sys.path, but it's strangely not working completely.
>
> Finally, I managed to run the program :
> - by launching D:\python25\python.exe -E -S in a console (which seems to
> prevent
> python from loading the paths)
> - then appending the application path to sys.path
> but it's really not fun working with this bloody windows console where cut and
> paste is impossible...
>
> So, here is my question:
> How can I force py2.5 to go and find the dependencies only in the 2.5
> site-packages ?
>
> Thanks in advance for your help.
>
> Dominique
>
> ___
> Tutor maillist - tu...@python.org
> To unsubscribe or change subscription options:
> http://mail.python.org/mailman/listinfo/tutor
>
forgot to hit reply all
>From wht the ole swiss cheese kinda recalls, just cd into the 2.5 main
dir from the windows command propmpt, and then you should be able to
type python /path/to/2.5/idlelib/idle.py, or whatever is on your
system.
If that's not it, then let me know, and I'll switch os's to make sure
what it was.
Also, there is a list specifically for window's python. pywin32.
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] exercise correct ??
On 6 September 2010 19:32, Roelof Wobben wrote:
> def index_of(val, seq, start=0):
> """
> >>> index_of(9, [1, 7, 11, 9, 10])
> 3
> >>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5))
> 3
> >>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
> 6
> >>> index_of('y', 'happy birthday')
> 4
> >>> index_of('banana', ['apple', 'banana', 'cherry', 'date'])
> 1
> >>> index_of(5, [2, 3, 4])
> -1
> >>> index_of('b', ['apple', 'banana', 'cherry', 'date'])
> -1
> """
> plek = 0
> if type(seq) == type([]):
> plek = seq.index(val)
> elif type(seq) == type(()):
> seq = list (seq)
> plek = seq.index(val)
> else :
> plek = seq.find(val)
> return plek
Not sure if this is correct but why don't you check for the index
attribute? It is part of both lists and strings. Also you can use
try/except to catch a ValueError. My version below, but I dislike the
list() usage...
def index_of(val, seq, start=0):
if hasattr(seq, 'index'):
try:
return seq.index(val, start)
except ValueError:
return -1
else:
try:
return list(seq).index(val, start)
except ValueError:
return -1
> File "C:\Users\wobben\workspace\oefeningen\src\test.py", line 70, in
> __main__.index_of
>
> Failed example:
>
> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
>
> Expected:
>
> 6
>
> Got:
>
> 3
>
> But in that tuple 5 is on position 3.
>
> Is the exercise here wrong ?
Looks like it, or it's a typo.
Greets
Sander
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] exercise correct ??
Hi Roelof, On 6 September 2010 18:32, Roelof Wobben wrote: >>>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4) > 6 > > But in that tuple 5 is on position 3. > > Is the exercise here wrong ? > > Not neccesarily... I notice that the call is similar to the previous test case, but has an extra parameter "4", and that but that tuple that's being searched contains other 5's. If the extra parameter is interpreted as a "starting index", then the next index of "5" starting at position 4, would indeed be 6. If my guesstimated intention of the test paramters is correct then there's nothing wrong with the excercise/test and your implementation of index_of needs to be enhanced to properly handle this extra parameter/new test case. Walter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Simple Python Problem
> > I think there is a trick in V2.7 to make it act more like v3 but someone > > else will need to tell you what it is... :-) >Other than changing the input() to raw_input() for Python 2 compatibility, And of course you can do that using input = raw_input > the following statement could be added to the beginning of the program > to allow your Python 2 program to use the Python 3 style print function. from __future__ import print_function >That would help. I wonder if we could create a module that would make v2.7 simulate v3 to a close degree? hmm... And is it sensible to try, should we not perhaps just accept the difference? Alan G. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] exercise correct ??
> Date: Mon, 6 Sep 2010 21:45:17 +0200
> Subject: Re: [Tutor] exercise correct ??
> From: sander.swe...@gmail.com
> To: rwob...@hotmail.com
> CC: tutor@python.org
>
> On 6 September 2010 19:32, Roelof Wobben wrote:
> > def index_of(val, seq, start=0):
> > """
> > >>> index_of(9, [1, 7, 11, 9, 10])
> > 3
> > >>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5))
> > 3
> > >>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
> > 6
> > >>> index_of('y', 'happy birthday')
> > 4
> > >>> index_of('banana', ['apple', 'banana', 'cherry', 'date'])
> > 1
> > >>> index_of(5, [2, 3, 4])
> > -1
> > >>> index_of('b', ['apple', 'banana', 'cherry', 'date'])
> > -1
> > """
> > plek = 0
> > if type(seq) == type([]):
> > plek = seq.index(val)
> > elif type(seq) == type(()):
> > seq = list (seq)
> > plek = seq.index(val)
> > else :
> > plek = seq.find(val)
> > return plek
>
> Not sure if this is correct but why don't you check for the index
> attribute? It is part of both lists and strings. Also you can use
> try/except to catch a ValueError. My version below, but I dislike the
> list() usage...
>
> def index_of(val, seq, start=0):
> if hasattr(seq, 'index'):
> try:
> return seq.index(val, start)
> except ValueError:
> return -1
> else:
> try:
> return list(seq).index(val, start)
> except ValueError:
> return -1
>
> > File "C:\Users\wobben\workspace\oefeningen\src\test.py", line 70, in
> > __main__.index_of
> >
> > Failed example:
> >
> > index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4)
> >
> > Expected:
> >
> > 6
> >
> > Got:
> >
> > 3
> >
> > But in that tuple 5 is on position 3.
> >
> > Is the exercise here wrong ?
>
> Looks like it, or it's a typo.
>
> Greets
> Sander
Hello Sander,
I agree that index is a part of string and list.
But not a part of a tuple.
As far as I know index is not a part of tuple so I have to convert it to a list
so I can use index.
Roelof
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] exercise correct ??
On 6 September 2010 22:28, Roelof Wobben wrote: > As far as I know index is not a part of tuple so I have to convert it to a > list so I can use index. As of version 2.6/3 a tuple does have index(). Not sure which version you are using. Greets Sander ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Simple Python Problem
>Other than changing the input() to raw_input() for Python 2 compatibility, > > > And of course you can do that using > > input = raw_input > > > > the following statement could be added to the beginning of the program > > to allow your Python 2 program to use the Python 3 style print function. > > from __future__ import print_function > > That would help. > I wonder if we could create a module that would make v2.7 simulate v3 to > a close degree? hmm... And is it sensible to try, should we not perhaps > just accept the difference? > > Alan G. > > Ah! I did not know that input = raw_input would work, thanks! I am sure someone could create such. However, to me, it would be more sensible to just program in v3. I have decided to code in only v3 since I do not have any previous code base to maintain and am still very much in learning mode. It seems that some of the more popular external modules such as NumPy and PyGame are also now v3 compatible. By the way, even though I am far from proficient with Python, it has already become a useful tool for me at work! -Bill ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] exercise correct ??
On 6 September 2010 21:45, Sander Sweers wrote: >> Is the exercise here wrong ? > > Looks like it, or it's a typo. Now that I had a better look the test is correct. Now it is up to you to figure out why your index_of() fails. Walter gave you a good hint. Greets Sander ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] slicing a string
Hi guys, Continuing my Python learning, I came across an exercise which asks me to take a string and reverse it. I understand that there is a function to do this i.e mytext.reverse() I imagine that the exercise author would rather I did this the hard way however. ;-) Assuming that mytext is "test", I've found that mytext[-1:-4:-1] doesn't work (as I expected it to) but that mytext[::-1] does. While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work? Thanks again, Chris ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] slicing a string
On 7 September 2010 00:14, lists wrote: > Assuming that mytext is "test", I've found that mytext[-1:-4:-1] > doesn't work (as I expected it to) but that mytext[::-1] does. > > While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work? How does it not "work"? What did you expect to happen? What did it do instead? Greets Sander ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] exercise correct ??
"Roelof Wobben" wrote # def index_of(val, seq, start=0): """ >>> index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4) 6 """ But I get this message : Failed example: index_of(5, (1, 2, 4, 5, 6, 10, 5, 5), 4) Expected: 6 Got: 3 # But in that tuple 5 is on position 3. Is the exercise here wrong ? No because the start position is 4 so you don;t see the 5 in position 3. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Multiple versions of python and paths problems
"Dominique" wrote
So, I tried to load the normal 2.5 Idle and unload ('remove')
everything related
to 2.6 from sys.path, but it's strangely not working completely.
How do you start IDLE? Is it via a desktop or start menu shortcut?
If so what is the startin folder specified as?
What happens when you run it from the command ine with no extra
parameters - what error do you get?
Do you have both versions of Python in your environment variables?
In which order?
Hint: Start a DOS session and type
SET PYTHONPATH
and
SET PATH
Finally, I managed to run the program :
- by launching D:\python25\python.exe -E -S in a console (which
seems to prevent
python from loading the paths) - then appending the application path
to sys.path
but it's really not fun working with this bloody windows console
where cut and
paste is impossible...
Set the Quick Edit option for the terminal it will save you a lot of
pain.
Cut n paste are then possible. In fact you should probably read the
Windows help on CMD too because there are a lot of settings/registry
tweaks that improves the use of the CMD prompt dramatically.
Also look at the WindowsPowerShell - it has a lot of this "out of the
box"
But that aside you shouldn't have to do all this!
How can I force py2.5 to go and find the dependencies only in the
2.5
site-packages ?
There are probably several ways round it, including creating a local
startup file.
But if the paths are right it should work, and you may need to create
a startup
DOS file to set them before executing python...
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] slicing a string
"lists" wrote Assuming that mytext is "test", I've found that mytext[-1:-4:-1] doesn't work (as I expected it to) but that mytext[::-1] does. While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work? It does work. But remember that slices give you the first item to one less than the second index, so for a 4 letter word you need an index of of -5... "test"[-1:-4:-1] 'tse' "test"[-1:-5:-1] 'tset' HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] slicing a string
>> Assuming that mytext is "test", I've found that mytext[-1:-4:-1] >> doesn't work (as I expected it to) but that mytext[::-1] does. >> >> While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work? > > How does it not "work"? What did you expect to happen? What did it do instead? > > Greets > Sander > Hi, assuming mytext is "test", word[-1:-4:-1] returns tse My understanding of how the index works on test would be: 0 1 2 3 t e s t -4 -3 -2 -1 So I just wasn't clear on what happened to the last 't' I expected to see. Cheer, Chris ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] slicing a string
>>> Assuming that mytext is "test", I've found that mytext[-1:-4:-1] >>> doesn't work (as I expected it to) but that mytext[::-1] does. >>> >>> While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work? >> >> How does it not "work"? What did you expect to happen? What did it do >> instead? >> >> Greets >> Sander >> > > Hi, assuming mytext is "test", word[-1:-4:-1] returns tse > > My understanding of how the index works on test would be: > > 0 1 2 3 > t e s t > -4 -3 -2 -1 > > So I just wasn't clear on what happened to the last 't' I expected to see. > > Cheer, > > Chris > Sorry I mean mytext[-1:-4:-1] not word[-1:-4:-1] :-S ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] slicing a string
On Tue, 7 Sep 2010 08:14:59 am lists wrote:
> Hi guys,
>
> Continuing my Python learning, I came across an exercise which asks
> me to take a string and reverse it.
>
> I understand that there is a function to do this i.e mytext.reverse()
You understand wrong :)
There is a function reversed() which takes any iterable object (a list,
a string, a tuple, a set, ...) and returns an iterator that yields the
items in reverse order:
>>> reversed("test")
but that's not useful in this case.
> I imagine that the exercise author would rather I did this the hard
> way however. ;-)
>
> Assuming that mytext is "test", I've found that mytext[-1:-4:-1]
> doesn't work (as I expected it to) but that mytext[::-1] does.
>
> While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work?
Remember that slice indexes fall *between* characters:
A slice of [-1:-4:-1] is equivalent to [3:0:-1].
>>> 'Test'[-1:-4:-1]
'tse'
>>> 'Test'[3:0:-1]
'tse'
So, what does this slice do? The slice indexes are equivalent to:
range(3, 0, -1)
=> [3, 2, 1]
Remember that the end position is excluded! Hence you reverse all the
characters in the string *except* the first.
--
Steven D'Aprano
___
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Simple Python Problem
On Tue, 7 Sep 2010 06:02:39 am ALAN GAULD wrote: > I wonder if we could create a module that would make v2.7 simulate v3 > to a close degree? hmm... And is it sensible to try, should we not > perhaps just accept the difference? from __future__ import print_function, unicode_literals from future_builtins import * will get you part of the way, but it's probably impossible to get the two to be *exactly* the same. -- Steven D'Aprano ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Arguments from the command line
On Tue, 7 Sep 2010 02:08:27 am Hugo Arts wrote: > sys.argv is a list of all arguments from the command line. However, > you'll rarely deal with it directly, there's various modules that > deal with handling arguments. I believe the current one is argparse: > http://docs.python.org/library/argparse.html#module-argparse In my experience, getopt is a gentler introduction to argument parsing, because it does much less :) optparse is another good one. All three are available up to Python 2.7, and possibly in 3.1 as well, I haven't checked. -- Steven D'Aprano ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] slicing a string
On Tue, Sep 7, 2010 at 12:44 AM, lists wrote: >>> Assuming that mytext is "test", I've found that mytext[-1:-4:-1] >>> doesn't work (as I expected it to) but that mytext[::-1] does. >>> >>> While that's fine, I just wondered why mytext[-1:-4:-1] doesn't work? >> >> How does it not "work"? What did you expect to happen? What did it do >> instead? >> >> Greets >> Sander >> > > Hi, assuming mytext is "test", word[-1:-4:-1] returns tse > > My understanding of how the index works on test would be: > > 0 1 2 3 > t e s t > -4 -3 -2 -1 > > So I just wasn't clear on what happened to the last 't' I expected to see. >>> "test"[0:3] 'tes' [m:n] shows the elements from m upto but excluding n. -- André Engels, andreeng...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] setattr vs __setattr__
On Mon, 6 Sep 2010 09:03:30 pm Rasjid Wilcox wrote: > I've been using > > for attr_name in name_list: > setattr(a, attr_name, getattr(b, attr_name)) > > to copy the attributes from one type of class to another, and it is > not quite as readable as I would like. The one-liner in the for loop is very concise. The problem is that concise is often the opposite of readable. So make it less concise: for name in name_list: obj = getattr(b, name) setattr(a, name, obj) Does that help? Another alternative, depending on the class, *might* be this: a.__dict__.update(b.__dict__) although that's a hack, and like all hacks, may not do what you expect for all classes. > Actually, I've just thought > that the best option would be to make both classes dictionary like > objects with automatic translation between a['foo'] and a.foo. How does that help you copy from one class to another? As I see it, it just adds more noise to the class. -- Steven D'Aprano ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Multiple versions of python and paths problems
On 2:59 PM, Dominique wrote: = but it's really not fun working with this bloody windows console where cut and paste is impossible... Cut and paste work fine in a Windows DOS console. Using Properties, the Options tab, turn on Quick-Edit mode. Once you've done that, you can select a rectangle of text in such a console by using click/drag. Then you copy it to the clipboard with right click. If you need to paste into the command line, something that's already in the clipboard, you can again use right click. It's also possible to do copy or past without changing any properties -- just use the right-click on the title bar. to mark, then copy, or to paste. DaveA ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Arguments from the command line
Alrighty! Thanks, everyone! On Mon, Sep 6, 2010 at 6:48 PM, Steven D'Aprano wrote: > On Tue, 7 Sep 2010 02:08:27 am Hugo Arts wrote: > > > sys.argv is a list of all arguments from the command line. However, > > you'll rarely deal with it directly, there's various modules that > > deal with handling arguments. I believe the current one is argparse: > > http://docs.python.org/library/argparse.html#module-argparse > > In my experience, getopt is a gentler introduction to argument parsing, > because it does much less :) > > optparse is another good one. > > All three are available up to Python 2.7, and possibly in 3.1 as well, I > haven't checked. > > > -- > Steven D'Aprano > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] setattr vs __setattr__
On 7 September 2010 08:55, Steven D'Aprano wrote: > On Mon, 6 Sep 2010 09:03:30 pm Rasjid Wilcox wrote: >> I've been using >> >> for attr_name in name_list: >> setattr(a, attr_name, getattr(b, attr_name)) >> >> to copy the attributes from one type of class to another, and it is >> not quite as readable as I would like. > > The one-liner in the for loop is very concise. The problem is that > concise is often the opposite of readable. So make it less concise: > > for name in name_list: > obj = getattr(b, name) > setattr(a, name, obj) > > Does that help? Yes, that does help. Such a simple and obvious thing (once someone has pointed it out) and addresses my concern with the one-liner that while easy to write, when looking back at it one has to look carefully and analyse it to be certain about what is going on. The two liner has a few more keystrokes but is much easier on the eyes. And easy on the eyes is important to me - it is why I find Python 'beautiful' in a way that most programming languages are not. Much thanks, Rasjid. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
