Re: [Tutor] Hello World in Python without space
On Fri, Jul 15, 2011 at 21:38, Steven D'Aprano wrote:
>
> Richard D. Moores wrote:
>
>> But that makes me wonder if there isn't a simpler way to do it with
>> Python -- to delete the contents of a file without deleting the file?
>
> Opening a file for writing will flush the contents.
>
> open(filename, 'w')
>
> will do it, taking advantage of Python's garbage collector to (eventually)
> close the file. The more careful way is hardly any harder:
>
> open(filename, 'w').close()
>
> and this ensures that the file isn't left open any longer than necessary.
open("C:/test/test.txt", 'w').close()
Good to know. Thanks, Steven.
Dick
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Re: [Tutor] IDLE/tk in 10.6
Luke Thomas Mergner wrote: [...] I'd like to try IDLE but there appears to be a known bug with 10.6's version of ActiveTCL. I've installed a newer version 8.5 via their website, but this has not fixed the problem. The module tkinter is still unable to load. Since both python and activeTCL are installed as "Frameworks" on my mac, I wonder if I need to tell python27 that there is another Tkinter installed elsewhere. Can anyone give me some advice? This is not really the sort of question we can likely help you with here. This is for learned about Python as a programming language, not the ins and outs of getting it running on various operating systems. You might get lucky and find another Mac user here who can advise you, but you will probably have more luck on the main Python list, python-l...@python.com (also available on usenet, comp.lang.python) or on a more specialist Mac forum. Good luck! -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Filling orders FIFO
Charles John wrote: Hi I am new to python and was wondering what the best way to create an order(bid and offer) queue, then match a bid and offer so that if bid==offer, creates a filled order FIFO in python cgi using mysql? Does anybody have any ideas? It would be greatly appreciated. The simplest way to use a queue is with a list: queue = [] You push items onto the queue with queue.append(item) and pop them off with queue.pop(0). However, popping items may be slow if the queue grows very large (tens of thousands of items). It might be better to use a deque (double ended queue) instead of a list: from collections import deque queue = deque() To push items onto the right hand side of the queue, then pop them off the left hand side: queue.append(item) queue.popleft() As for the rest of your question, I don't understand what you mean by an order(bid and offer) queue. Perhaps you could give an example of what you mean. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hello World in Python without space
Richard D. Moores wrote: But that makes me wonder if there isn't a simpler way to do it with Python -- to delete the contents of a file without deleting the file? Opening a file for writing will flush the contents. open(filename, 'w') will do it, taking advantage of Python's garbage collector to (eventually) close the file. The more careful way is hardly any harder: open(filename, 'w').close() and this ensures that the file isn't left open any longer than necessary. -- Steven ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Hello World in Python without space
On Fri, Jul 15, 2011 at 17:16, Dave Angel wrote:
> On 07/15/2011 07:39 PM, Richard D. Moores wrote:
>> with open("C:/test/test.txt", "a") as file_object:
>> print("Hello, world!", file=file_object)
>>
>> Yes, that works for me with Windows Vista. However, if test.txt is
>> empty, it puts in a blank line as line 1; line 2 is "Hello, world!".
>>
>> Dick
>> _
>
> I expect that your extra newline was already in the "empty" file. It cannot
> have anything to do with using the forward slash for the filename.
I see that you are correct. It seems that selecting all the text in a
text file (in Notepad), then hitting the delete key doesn't guarantee
that the file will be left truly blank. The way that consistently
works for me is to place the cursor in the upper left corner of the
file and hold down the delete key.
Running
with open("C:/test/test.txt", "w") as file_object:
print(file=file_object)
Also works.
But that makes me wonder if there isn't a simpler way to do it with
Python -- to delete the contents of a file without deleting the file?
Dick
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Re: [Tutor] Hello World in Python without space
On 07/15/2011 07:39 PM, Richard D. Moores wrote:
On Fri, Jul 15, 2011 at 16:21, xDog Walker wrote:
I believe on Windows, you can almost always use a forward slash in a path:
C:/somewhere/somewhereelse/
with open("C:/test/test.txt", "a") as file_object:
print("Hello, world!", file=file_object)
Yes, that works for me with Windows Vista. However, if test.txt is
empty, it puts in a blank line as line 1; line 2 is "Hello, world!".
Dick
_
I expect that your extra newline was already in the "empty" file. It
cannot have anything to do with using the forward slash for the filename.
DaveA
--
DaveA
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Re: [Tutor] Hello World in Python without space
On Fri, Jul 15, 2011 at 16:21, xDog Walker wrote:
> I believe on Windows, you can almost always use a forward slash in a path:
> C:/somewhere/somewhereelse/
with open("C:/test/test.txt", "a") as file_object:
print("Hello, world!", file=file_object)
Yes, that works for me with Windows Vista. However, if test.txt is
empty, it puts in a blank line as line 1; line 2 is "Hello, world!".
Dick
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Re: [Tutor] Hello World in Python without space
On Friday 2011 July 15 15:58, Richard D. Moores wrote:
> On Fri, Jul 15, 2011 at 14:47, Stefan Behnel wrote:
> > Richard D. Moores, 15.07.2011 23:21:
> >> What do I do to test.txt to make it "an object with a write(string)
> >> method"?
> >
> > Oh, there are countless ways to do that, e.g.
> >
> > class Writable(object):
> > def __init__(self, something):
> > print("Found a %s" % something))
> > def write(self, s):
> > print(s)
> >
> > print("Hello, world!", file=Writable("C:\\test\\test.txt"))
> >
> > However, I'm fairly sure what you want is this:
> >
> > with open("C:\\test\\test.txt", "w") as file_object:
> > print("Hello, world!", file=file_object)
>
> Yes, went with
>
> with open("C:\\test\\test.txt", "a+") as file_object:
> print("Hello, world!", file=file_object)
>
> > Look up "open()" (open a file) and the "with statement" (used here
> > basically as a safe way to make sure the file is closed after writing).
> >
> > Also note that "\t" refers to a TAB character in Python, you used this
> > twice in your file path string.
I believe on Windows, you can almost always use a forward slash in a path:
C:/somewhere/somewhereelse/
--
I have seen the future and I am not in it.
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Re: [Tutor] Hello World in Python without space
On Fri, Jul 15, 2011 at 14:47, Stefan Behnel wrote:
> Richard D. Moores, 15.07.2011 23:21:
>> What do I do to test.txt to make it "an object with a write(string)
>> method"?
>
> Oh, there are countless ways to do that, e.g.
>
> class Writable(object):
> def __init__(self, something):
> print("Found a %s" % something))
> def write(self, s):
> print(s)
>
> print("Hello, world!", file=Writable("C:\\test\\test.txt"))
>
> However, I'm fairly sure what you want is this:
>
> with open("C:\\test\\test.txt", "w") as file_object:
> print("Hello, world!", file=file_object)
Yes, went with
with open("C:\\test\\test.txt", "a+") as file_object:
print("Hello, world!", file=file_object)
> Look up "open()" (open a file) and the "with statement" (used here basically
> as a safe way to make sure the file is closed after writing).
>
> Also note that "\t" refers to a TAB character in Python, you used this twice
> in your file path string.
Oops. I'd forgotten about that.
Thanks very much, Stefan and Donald.
Dick
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Re: [Tutor] Hello World in Python without space
Richard D. Moores, 15.07.2011 23:21:
On Sun, Jul 10, 2011 at 05:05, Peter Otten wrote:
>>> help(print)
shows
print(...)
print(value, ..., sep=' ', end='\n', file=sys.stdout)
Prints the values to a stream, or to sys.stdout by default.
Optional keyword arguments:
file: a file-like object (stream); defaults to the current sys.stdout.
sep: string inserted between values, default a space.
end: string appended after the last value, default a newline.
I didn't know that printing to a file with print() was possible, so I tried
>>> print("Hello, world!", file="C:\test\test.txt")
Traceback (most recent call last):
File "", line 1, in
builtins.AttributeError: 'str' object has no attribute 'write'
>>>
And the docs at
tell me
"The file argument must be an object with a write(string) method; if
it is not present or None, sys.stdout will be used."
What do I do to test.txt to make it "an object with a write(string) method"?
Oh, there are countless ways to do that, e.g.
class Writable(object):
def __init__(self, something):
print("Found a %s" % something))
def write(self, s):
print(s)
print("Hello, world!", file=Writable("C:\\test\\test.txt"))
However, I'm fairly sure what you want is this:
with open("C:\\test\\test.txt", "w") as file_object:
print("Hello, world!", file=file_object)
Look up "open()" (open a file) and the "with statement" (used here
basically as a safe way to make sure the file is closed after writing).
Also note that "\t" refers to a TAB character in Python, you used this
twice in your file path string.
Stefan
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Re: [Tutor] Hello World in Python without space
On Sun, Jul 10, 2011 at 05:05, Peter Otten <__pete...@web.de> wrote:
> >>> help(print)
>
> shows
>
> print(...)
> print(value, ..., sep=' ', end='\n', file=sys.stdout)
>
> Prints the values to a stream, or to sys.stdout by default.
> Optional keyword arguments:
> file: a file-like object (stream); defaults to the current sys.stdout.
> sep: string inserted between values, default a space.
> end: string appended after the last value, default a newline.
I didn't know that printing to a file with print() was possible, so I tried
>>> print("Hello, world!", file="C:\test\test.txt")
Traceback (most recent call last):
File "", line 1, in
builtins.AttributeError: 'str' object has no attribute 'write'
>>>
And the docs at
tell me
"The file argument must be an object with a write(string) method; if
it is not present or None, sys.stdout will be used."
What do I do to test.txt to make it "an object with a write(string) method"?
Thanks,
Dick Moores
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[Tutor] Filling orders FIFO
Hi I am new to python and was wondering what the best way to create an order(bid and offer) queue, then match a bid and offer so that if bid==offer, creates a filled order FIFO in python cgi using mysql? Does anybody have any ideas? It would be greatly appreciated. Best chuck ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] IDLE/tk in 10.6
Hi, I am not a professional programmer, but just trying to learn. I'm running Mac 10.6 Snow Leopard. I used MacPorts to install python26, python27, and python3. My python interpreter loads 2.7.2 after I ran the python_select command, which is added via MacPorts I think. I'd like to try IDLE but there appears to be a known bug with 10.6's version of ActiveTCL. I've installed a newer version 8.5 via their website, but this has not fixed the problem. The module tkinter is still unable to load. Since both python and activeTCL are installed as "Frameworks" on my mac, I wonder if I need to tell python27 that there is another Tkinter installed elsewhere. Can anyone give me some advice? >>> import Tkinter Traceback (most recent call last): File "", line 1, in File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 39, in import _tkinter # If this fails your Python may not be configured for Tk ImportError: No module named _tkinter Luke Mergner lmerg...@gmail.com___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
