[Tutor] running a .py file from the comand line
Hello, I am running Python 3.6 in a Window 7 environment. I have a python script that I am trying to run from the command line. The script is from a Learning to Program file demonstrating event driven programming. I have copied it to a file named Ascii Keys.py into my user directory c:\Users\Rex I try to execute the file by typing python Ascii Keys.py at the command line and receive the following message: python: can't open file 'Ascii': [errno2] no such file or directory I expected the python .py file to open and run. I check with the path command and receive among other paths these to paths to Python. c:\Users\Rex/AppData\Local\Programs\Python\Python36-32\Scripts c:\Users\Rex/AppData\Local\Programs\Python\Python36-32 I also load python from c:\Users\Rex and try running Ascii Keys from >> and get the following error: File "", line 1 Ascii Keys SyntaxError: invalid syntax Why doesn't python open my file? Also, in windows explorer, I tried to find the above paths and could not see AppData under c:\Users\Rex What am I missing here? import msvcrt import sys # First the event handlers def doKeyEvent(key): if key == '\x00' or key == '\xe0': key = msvcrt.getch() print ( ord(key), ' ', end='') sys.stdout.flush() # make sure it appears on screen def doQuit(key): print() # force a new line raise SystemExit # first clear some screen space lines = 25 for n in range(lines): print() # Now the main event-loop while True: ky = msvcrt.getch() if len(str(ky)) != 0: # we have a real event if " " in str(ky): doQuit(ky) else: doKeyEvent(ky) ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] running a .py file from the comand line
On 02/04/18 01:46, Rex Florian via Tutor wrote: > Hello, > > I am running Python 3.6 in a Window 7 environment. > I have a python script > that I am trying to run from the command line. > I have copied it to a file named Ascii Keys.py into my user directory > c:\Users\Rex > > I try to execute the file by typing python Ascii Keys.py Try python c:\Users\Rex\"ascii keys.py" Note the quotes to cater for the space. > python: can't open file 'Ascii': [errno2] no such file or directory The space confuses windows CMD, so it thinks you have two files called 'Ascii' and 'keys.py' By quoting the name it should see it as a single file name. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] pythonic
On 02/04/18 04:19, Steven D'Aprano wrote: > On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote: >> On01/04/18 20:20, Albert-Jan Roskam wrote: >>> fmt="%Y-%m-%d %H:%M\n" >>> f.write(now.strftime(fmt)) >>> Lately I've been using format(), which uses __format__, because I find it >>> slightly more readable: >>> format(datetime.now(), "%Y-%m-%d %H:%M") >> Interesting, >> I didn't know that format() recognised the datetime format codes. > It doesn't. It is the datetime object that recognises them. format() > merely passes the format string to the datetime.__format__ method, which > is what recognises the codes. It doesn't care what it is. Aha! That makes sense. I've never really used format() so have never bothered to find out how it works. To the point that until this thread I hadn't realized we even had a __format__() operator. As I said, I need to do some reading. Obviously a gap in my python education. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] pythonic
On 04/02/2018 02:56 AM, Alan Gauld via Tutor wrote: > On 02/04/18 04:19, Steven D'Aprano wrote: >> On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote: >>> On01/04/18 20:20, Albert-Jan Roskam wrote: fmt="%Y-%m-%d %H:%M\n" f.write(now.strftime(fmt)) Lately I've been using format(), which uses __format__, because I find it slightly more readable: format(datetime.now(), "%Y-%m-%d %H:%M") >>> Interesting, >>> I didn't know that format() recognised the datetime format codes. >> It doesn't. It is the datetime object that recognises them. format() >> merely passes the format string to the datetime.__format__ method, which >> is what recognises the codes. It doesn't care what it is. > Aha! That makes sense. I've never really used format() so have never > bothered to find out how it works. To the point that until this thread I > hadn't realized we even had a __format__() operator. > > As I said, I need to do some reading. Obviously a gap in my python > education. > so since we're all learning things here, how would this play out with the new f-strings? ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] pythonic
> On Mar 30, 2018, at 04:15, George Fischhof wrote: > > 2.) > argparse > > it is good, but you can write more Pythonic code using click > https://pypi.python.org/pypi/click/ > it is also Pythonic to use / know the Python ecosystem (the packages) It’s just as (if not more) pythonic to use the standard libraries. It’s very common in a professional environment to not have access to outside (i.e., internet) resources. I wouldn’t venture into Pypi unless there’s something you can’t do well with what’s already provided by default. — David Rock da...@graniteweb.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] pythonic
On Mon, Apr 2, 2018 at 9:01 AM, David Rock wrote: > It’s just as (if not more) pythonic to use the standard libraries. It’s very > common in a professional environment to not have access to outside (i.e., > internet) resources. I wouldn’t venture into Pypi unless there’s something > you can’t do well with what’s already provided by default. +1. Use standard libraries; most places I've worked didn't allow a lot of non-standard library code at all. If something is in the standard library you have some level of assurance that the maintenance is moderated and monitored. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] pythonic
On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:
> On 04/02/2018 02:56 AM, Alan Gauld via Tutor wrote:
> > On 02/04/18 04:19, Steven D'Aprano wrote:
> >> On Sun, Apr 01, 2018 at 10:58:51PM +0100, Alan Gauld via Tutor wrote:
> >>> On01/04/18 20:20, Albert-Jan Roskam wrote:
> fmt="%Y-%m-%d %H:%M\n"
> f.write(now.strftime(fmt))
> Lately I've been using format(), which uses __format__, because I find
> it slightly more readable:
> format(datetime.now(), "%Y-%m-%d %H:%M")
> >>> Interesting,
> >>> I didn't know that format() recognised the datetime format codes.
> >> It doesn't. It is the datetime object that recognises them. format()
> >> merely passes the format string to the datetime.__format__ method, which
> >> is what recognises the codes. It doesn't care what it is.
> > Aha! That makes sense. I've never really used format() so have never
> > bothered to find out how it works. To the point that until this thread I
> > hadn't realized we even had a __format__() operator.
> >
> > As I said, I need to do some reading. Obviously a gap in my python
> > education.
> >
>
> so since we're all learning things here, how would this play out with
> the new f-strings?
I don't think f-strings are even a bit Pythonic.
They look like string constants, but they're actually a hidden call to
eval().
py> x = 2
py> f'hello {3*x}'
'hello 6'
So they can execute arbitrary code that has arbitrary side-effects:
py> L = []
py> f'hello {L.append(1) or 99}'
'hello 99'
py> L
[1]
By my count, they violate at least three of the Zen of Python:
Explicit is better than implicit.
Simple is better than complex.
Special cases aren't special enough to break the rules.
They can only be used once, and are not re-usable (unlike proper
templates):
py> x = 2
py> template = f'x = {x}' # gets the value of x now
py> print(template)
x = 2
py> x = 99
py> print(template) # still has the old value of x
x = 2
However, they do use the same mechanism as format():
py> from datetime import datetime
py> t = datetime.now()
py> format(t, '%H:%M')
'23:22'
py> f'{t:%H:%M}'
'23:22'
--
Steve
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Re: [Tutor] pythonic
Steven D'Aprano wrote:
> On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:
>> so since we're all learning things here, how would this play out with
>> the new f-strings?
>
> I don't think f-strings are even a bit Pythonic.
>
> They look like string constants, but they're actually a hidden call to
> eval().
But because you cannot f-ify a string variable (without an additional eval()
call) you aren't tempted to feed them user-provided data.
> They can only be used once, and are not re-usable (unlike proper
> templates):
You can't eat your cake an have it. As "proper templates" they would indeed
be as dangerous as eval().
> By my count, they violate at least three of the Zen of Python:
>
> Explicit is better than implicit.
> Simple is better than complex.
> Special cases aren't special enough to break the rules.
As I'm getting tired of writing
"...{foo}...{bar}...".format(foo=foo, bar=bar, ...)
lately I'd say they win big in the "practicality beats you-name-it" area.
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Re: [Tutor] pythonic
On 04/02/2018 08:28 AM, Peter Otten wrote:
> Steven D'Aprano wrote:
>
>> On Mon, Apr 02, 2018 at 06:49:52AM -0600, Mats Wichmann wrote:
>
>>> so since we're all learning things here, how would this play out with
>>> the new f-strings?
>>
>> I don't think f-strings are even a bit Pythonic.
>>
>> They look like string constants, but they're actually a hidden call to
>> eval().
>
> But because you cannot f-ify a string variable (without an additional eval()
> call) you aren't tempted to feed them user-provided data.
>
>> They can only be used once, and are not re-usable (unlike proper
>> templates):
>
> You can't eat your cake an have it. As "proper templates" they would indeed
> be as dangerous as eval().
>
>> By my count, they violate at least three of the Zen of Python:
>>
>> Explicit is better than implicit.
>> Simple is better than complex.
>> Special cases aren't special enough to break the rules.
>
> As I'm getting tired of writing
>
> "...{foo}...{bar}...".format(foo=foo, bar=bar, ...)
>
> lately I'd say they win big in the "practicality beats you-name-it" area.
so swooping back to the origial code, it seems there are several options
for expressing the output. Picking one of the lines (and replacing the
writes to a file with prints for simplicity):
print("Date: {}-{}-{} {}:{}\n".format(now.year,
now.month,
now.day,
now.hour,
now.minute))
print("Date:", format(now, "%Y-%m-%d %H:%M"))
print(f"Date: {now:%Y-%m-%d %H:%M}")
those aren't exactly identical, since the using %m-%d form causes
zero-padding:
Date: 2018-4-2 10:23
Date: 2018-04-02 10:23
Date: 2018-04-02 10:23
For me, I don't know if the f-string version is the most Pythonic, but
it has an appealing conciseness in this particular context :)
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Re: [Tutor] running a .py file from the comand line
On Mon, Apr 2, 2018 at 8:53 AM, Alan Gauld via Tutor wrote: > > Try > > python c:\Users\Rex\"ascii keys.py" > > Note the quotes to cater for the space. > >> python: can't open file 'Ascii': [errno2] no such file or directory > > The space confuses windows CMD, so it thinks you have > two files called 'Ascii' and 'keys.py' Unlike Unix, this is not due to the shell in Windows. A process is started with a raw command line string. For a C/C++ application, the default process entry point is provided by the C runtime and does the setup work to call the application entry point (e.g. [w]main). This includes parsing the command line into an argv array according to documented rules [1]. An application can also call GetCommandLineW [2] and CommandLineToArgvW [3]. [1]: https://docs.microsoft.com/en-us/cpp/cpp/parsing-cpp-command-line-arguments [2]: https://msdn.microsoft.com/en-us/library/ms683156 [3]: https://msdn.microsoft.com/en-us/library/bb776391 CPython is written in C and uses the standard Windows C/C++ wmain and wWinMain application entry points. If you run "python C:\Users\Rex\Ascii Keys.py", the C runtime parses this into an argv array with 3 items: "python", "C:\Users\Rex\Ascii", and "Keys.py". Thus Python tries to open a script named "C:\Users\Rex\Ascii". ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] running a .py file from the comand line
On 04/02/2018 11:41 AM, eryk sun wrote: > On Mon, Apr 2, 2018 at 8:53 AM, Alan Gauld via Tutor wrote: >> >> Try >> >> python c:\Users\Rex\"ascii keys.py" >> >> Note the quotes to cater for the space. >> >>> python: can't open file 'Ascii': [errno2] no such file or directory >> >> The space confuses windows CMD, so it thinks you have >> two files called 'Ascii' and 'keys.py' > > Unlike Unix, this is not due to the shell in Windows. A process is > started with a raw command line string. For a C/C++ application, the > default process entry point is provided by the C runtime and does the > setup work to call the application entry point (e.g. [w]main). This > includes parsing the command line into an argv array according to > documented rules [1]. An application can also call GetCommandLineW [2] > and CommandLineToArgvW [3]. > > [1]: > https://docs.microsoft.com/en-us/cpp/cpp/parsing-cpp-command-line-arguments > [2]: https://msdn.microsoft.com/en-us/library/ms683156 > [3]: https://msdn.microsoft.com/en-us/library/bb776391 > > CPython is written in C and uses the standard Windows C/C++ wmain and > wWinMain application entry points. If you run "python > C:\Users\Rex\Ascii Keys.py", the C runtime parses this into an argv > array with 3 items: "python", "C:\Users\Rex\Ascii", and "Keys.py". > Thus Python tries to open a script named "C:\Users\Rex\Ascii". so in summary... if you have things set up so you can click-to-launch, filenames with spaces in them will work, but you'll be better off avoiding them, esp. if you intend to launch from a command line. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
[Tutor] Python help
Hi, I am trying to write a code with if statements but the code keeps just
repeating and not carrying on.
I am trying to get user to input a grade, either A, B, C, D, E or F and
trying to have an error message if anything but these values are inputted.
This is what i've wrote so far:
while True:
try:
Grade = int(raw_input("Please enter your Grade: "))
except ValueError:
print("Error, Please enter A, B, C, D, E or F")
continue
if Grade <> 'A','B','C','D','E','F':
print ("Error, Please enter A, B, C, D, E or F")
continue
else:#Grade succesfully completed, and we're happy with its value.
#ready to exit the loop.
break
When trying to run it just writes the error message for any letter you
input.
Any hep would be appreciated thank you!
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Re: [Tutor] pythonic
On Mon, Apr 02, 2018 at 04:28:10PM +0200, Peter Otten wrote:
> > They look like string constants, but they're actually a hidden call to
> > eval().
>
> But because you cannot f-ify a string variable (without an additional eval()
> call) you aren't tempted to feed them user-provided data.
If only that were the case...
https://mail.python.org/pipermail/python-list/2018-March/731967.html
He reads f-strings from user-supplied data, then evals them.
But its okay, he's only doing it within his own organisation, and we all
know that "insiders" are always 100% trusted. "Insider attack" is just a
pair of words. Right?
> As I'm getting tired of writing
>
> "...{foo}...{bar}...".format(foo=foo, bar=bar, ...)
You can write:
template.format(**(locals()))
or possibly nicer still:
template.format_map(locals())
--
Steve
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Re: [Tutor] Python help
On Mon, Apr 02, 2018 at 11:44:39PM +0100, Shannon Evans via Tutor wrote:
> Hi, I am trying to write a code with if statements but the code keeps just
> repeating and not carrying on.
> I am trying to get user to input a grade, either A, B, C, D, E or F and
> trying to have an error message if anything but these values are inputted.
> This is what i've wrote so far:
>
> while True:
> try:
> Grade = int(raw_input("Please enter your Grade: "))
Here you convert the user's input into an integer, a number such as 1,
2, 57, 92746 etc. If that *fails*, you run this block:
> except ValueError:
> print("Error, Please enter A, B, C, D, E or F")
> continue
and start again.
If it succeeds, because the user entered (let's say) 99, then you run
another test:
> if Grade <> 'A','B','C','D','E','F':
> print ("Error, Please enter A, B, C, D, E or F")
> continue
That will ALWAYS fail, because you are trying to compare the integer 99
(for example) with the tuple of six characters:
99 <> ('A', 'B','C','D','E','F')
which is always false. So that block will ALWAYS fail, and you always go
back to the start.
--
Steve
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Re: [Tutor] Python help
On 02/04/18 23:44, Shannon Evans via Tutor wrote:
> Hi, I am trying to write a code with if statements but the code keeps just
> repeating and not carrying on.
There are quite a few problems here, see comments below.
> while True:
> try:
> Grade = int(raw_input("Please enter your Grade: "))
You are trying to convert the input to an integer.
But A-F will not convert so thats the first problem
right there.
> except ValueError:
> print("Error, Please enter A, B, C, D, E or F")
> continue
And here you prompt for an A-F input not an integer.
> if Grade <> 'A','B','C','D','E','F':
This doesn't do what you think. It tests to see if Grade
is not equal to a tuple of values ('A','B','C','D','E','F')
You need to use 'in' instead. That will check whether
or not Grade is *one* of the values in the tuple.
if Grade not in 'A','B','C','D','E','F':
> print ("Error, Please enter A, B, C, D, E or F")
> continue
> else:#Grade succesfully completed, and we're happy with its value.
> #ready to exit the loop.
> break
Taking out the conversion to int() would be a good start.
Then change the if test to use 'in'.
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
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Re: [Tutor] Python help
On Tue, Apr 03, 2018 at 01:00:59AM +0100, Alan Gauld via Tutor wrote:
> You need to use 'in' instead. That will check whether
> or not Grade is *one* of the values in the tuple.
>
> if Grade not in 'A','B','C','D','E','F':
Actually, that returns a tuple consisting of a flag plus five more
strings:
py> 'A' in 'A','B','C', 'D', 'E', 'F'
(True, 'B','C', 'D', 'E', 'F')
We need to put round brackets (parentheses) around the scores:
if Grade not in ('A','B','C','D','E','F'):
Don't be tempted to take a short-cut:
# WRONG!
if Grade not in 'ABCDEF':
as that would accepted grades like "CDEF" and "BC".
--
Steve
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Re: [Tutor] Python help
On 03/04/18 01:19, Steven D'Aprano wrote:
> On Tue, Apr 03, 2018 at 01:00:59AM +0100, Alan Gauld via Tutor wrote:
>
>> You need to use 'in' instead. That will check whether
>> or not Grade is *one* of the values in the tuple.
>>
>> if Grade not in 'A','B','C','D','E','F':
> Actually, that returns a tuple consisting of a flag plus five more
> strings:
>
> py> 'A' in 'A','B','C', 'D', 'E', 'F'
> (True, 'B','C', 'D', 'E', 'F')
>
> We need to put round brackets (parentheses) around the scores:
>
> if Grade not in ('A','B','C','D','E','F'):
Oops, yes, a cut n' paste error, I forgot to add the parens.
mea culpa!
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos
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Re: [Tutor] Python help
On 03/04/18 01:19, Steven D'Aprano wrote: > >> if Grade not in 'A','B','C','D','E','F': > Actually, that returns a tuple consisting of a flag plus five more > strings: > > py> 'A' in 'A','B','C', 'D', 'E', 'F' > (True, 'B','C', 'D', 'E', 'F') Although in the context of the program the colon at the end ensures we get a syntax error so the mistake is found pretty quickly... -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
