Re: How to write a simple shell loop in python?

2009-01-23 Thread Dietrich Bollmann 
[Sorry for top posting - I had a HD problem and lost the original mails]

Hi Saul, Steve, Ben, James, Scott David and James!

Thank you all very much for your help! I finally got rid of the extra
space and also understood why the space was printed :)

After using Steve's 'input = raw_input($ )' solution for a while -
it does exactly what I want and is the fastest fix also - I wanted
command line editing and switched to the cmd.Cmd module.

Special thanks to James Mills for writing his own solution!

I would like to use your component - but cmd.Cmd is just perfect
for my purpose and I want to run my program without the need to
install any new module (I am writing the program for somebody else).

I got interested in circuits though - but the homepage
http://trac.softcircuit.com.au/circuits/ (currently?) seems not to be
available.

Thanks again for your answers :)

Dietrich


PS: There is a little tutorial for cmd.Cmd here:

  - http://www.doughellmann.com/PyMOTW/cmd/index.html

The documentation is here:

  - http://docs.python.org/library/cmd.html

(got it from Ben Finney's post) 


On Wed, 2009-01-21 at 08:37 -0500, Steve Holden wrote:
 Dietrich Bollmann wrote:
  Hi,
  
  I am trying to write a simple shell loop in Python.
  
  My simple approach works fine - but the first output line after entering
  something is always indented by one blank.  
  
  Is there any logic explanation for this?  
  How can I get rid of the blank?
  Is there a smarter way to write a simple shell loop which would work
  better?
  
  Thanks, Dietrich
  
  
  Here my approach:
  
  $ python
  Python 2.5.2 (r252:60911, Jan  4 2009, 17:40:26) 
  [GCC 4.3.2] on linux2
  Type help, copyright, credits or license for more information.
  import sys
  while (1):
  ... print $ ,
  ... input = sys.stdin.readline()
 Just replace the lines above with
 
 input = raw_input($ )
 
 and you'll be fine. The , in the print statement causes the
 interpreter to set a flag to emit a space before the next output unless
 it has just printed a newline. The newline, of course, is provided by
 the input, so the next print emits a space since it *hasn't* just
 emitted a newline.
 
 regards
  Steve
 
  ... input = input.strip()
  ... print input
  ... print input
  ... print input
  ... 
  $ one
   one
  one
  one
  $ two
   two
  two
  two
  $ three
   three
  three
  three
  $ 
  Traceback (most recent call last):
File stdin, line 3, in module
  KeyboardInterrupt
  
  
  --
  http://mail.python.org/mailman/listinfo/python-list
  
 
 

--
http://mail.python.org/mailman/listinfo/python-list

Re: How to write a simple shell loop in python?

2009-01-21 Thread Steve Holden 
Dietrich Bollmann wrote:
 Hi,
 
 I am trying to write a simple shell loop in Python.
 
 My simple approach works fine - but the first output line after entering
 something is always indented by one blank.  
 
 Is there any logic explanation for this?  
 How can I get rid of the blank?
 Is there a smarter way to write a simple shell loop which would work
 better?
 
 Thanks, Dietrich
 
 
 Here my approach:
 
 $ python
 Python 2.5.2 (r252:60911, Jan  4 2009, 17:40:26) 
 [GCC 4.3.2] on linux2
 Type help, copyright, credits or license for more information.
 import sys
 while (1):
 ... print $ ,
 ... input = sys.stdin.readline()
Just replace the lines above with

input = raw_input($ )

and you'll be fine. The , in the print statement causes the
interpreter to set a flag to emit a space before the next output unless
it has just printed a newline. The newline, of course, is provided by
the input, so the next print emits a space since it *hasn't* just
emitted a newline.

regards
 Steve

 ... input = input.strip()
 ... print input
 ... print input
 ... print input
 ... 
 $ one
  one
 one
 one
 $ two
  two
 two
 two
 $ three
  three
 three
 three
 $ 
 Traceback (most recent call last):
   File stdin, line 3, in module
 KeyboardInterrupt
 
 
 --
 http://mail.python.org/mailman/listinfo/python-list
 


-- 
Steve Holden+1 571 484 6266   +1 800 494 3119
Holden Web LLC  http://www.holdenweb.com/

--
http://mail.python.org/mailman/listinfo/python-list

Re: How to write a simple shell loop in python?

2009-01-21 Thread Scott David Daniels 

Dietrich Bollmann wrote:

I am trying to write a simple shell loop in Python.

My simple approach works fine - but the first output line after entering
something is always indented by one blank.  
Is there any logic explanation for this?  

Yes

How can I get rid of the blank?

By not asking for it with the comma.



while (1):

... print $ ,
... input = sys.stdin.readline()
... input = input.strip()
... print input
... print input
... print input
... 
$ one

The one and \n above are from stdin, not stdout.  So stdout thinks
it is still on the same line as the $.

 one

The space separates the 'one' from the '$ ' that it output to stdout
above.

one
one


--Scott David Daniels
scott.dani...@acm.org


--
http://mail.python.org/mailman/listinfo/python-list

How to write a simple shell loop in python?

2009-01-20 Thread Dietrich Bollmann 
Hi,

I am trying to write a simple shell loop in Python.

My simple approach works fine - but the first output line after entering
something is always indented by one blank.  

Is there any logic explanation for this?  
How can I get rid of the blank?
Is there a smarter way to write a simple shell loop which would work
better?

Thanks, Dietrich


Here my approach:

$ python
Python 2.5.2 (r252:60911, Jan  4 2009, 17:40:26) 
[GCC 4.3.2] on linux2
Type help, copyright, credits or license for more information.
 import sys
 while (1):
... print $ ,
... input = sys.stdin.readline()
... input = input.strip()
... print input
... print input
... print input
... 
$ one
 one
one
one
$ two
 two
two
two
$ three
 three
three
three
$ 
Traceback (most recent call last):
  File stdin, line 3, in module
KeyboardInterrupt
 


--
http://mail.python.org/mailman/listinfo/python-list

Re: How to write a simple shell loop in python?

2009-01-20 Thread Saul Spatz 

Dietrich Bollmann wrote:

Hi,

I am trying to write a simple shell loop in Python.

My simple approach works fine - but the first output line after entering
something is always indented by one blank.  

Is there any logic explanation for this?  
How can I get rid of the blank?

Is there a smarter way to write a simple shell loop which would work
better?

Thanks, Dietrich


Here my approach:

$ python
Python 2.5.2 (r252:60911, Jan  4 2009, 17:40:26) 
[GCC 4.3.2] on linux2

Type help, copyright, credits or license for more information.
import sys
while (1):

... print $ ,
... input = sys.stdin.readline()
... input = input.strip()
... print input
... print input
... print input
... 
$ one

 one
one
one
$ two
 two
two
two
$ three
 three
three
three
$ 
Traceback (most recent call last):

  File stdin, line 3, in module
KeyboardInterrupt


Strange.  I don't have an explanation, but experiment shows that if you 
change print $ , to print $  (that is, leave out the comma) then the 
leading blank is not printed.  This behavior doesn't depend on the 
print input statement's being in a loop.


By the way, you don't need parens around the loop guard in python:
while 1: (or as I prefer, while True:) work just fine.

Saul
--
http://mail.python.org/mailman/listinfo/python-list

Re: How to write a simple shell loop in python?

2009-01-20 Thread James Mills 
On Wed, Jan 21, 2009 at 3:12 PM, Saul Spatz ssp...@kcnet.com wrote:
 Strange.  I don't have an explanation, but experiment shows that if you
 change print $ , to print $  (that is, leave out the comma) then the
 leading blank is not printed.  This behavior doesn't depend on the print
 input statement's being in a loop.

 By the way, you don't need parens around the loop guard in python:
 while 1: (or as I prefer, while True:) work just fine.

http://codepad.org/f2XSwsPo

This component I wrote - just for the hell of it - (just for this thread)
works nicely :)

cheers
James
--
http://mail.python.org/mailman/listinfo/python-list

Re: How to write a simple shell loop in python?

2009-01-20 Thread Ben Finney 
Dietrich Bollmann dir...@web.de writes:

 I am trying to write a simple shell loop in Python.

You should investigate the ‘cmd’ module in the standard library
URL:http://docs.python.org/library/cmd.html.

 My simple approach works fine - but the first output line after
 entering something is always indented by one blank.

You should investigate the meaning of a comma ‘,’ in the ‘print’
statement (hint: it can affect subsequent ‘print’ statements)
URL:http://docs.python.org/reference/simple_stmts.html#the-print-statement.

-- 
 \   “Anyone who puts a small gloss on [a] fundamental technology, |
  `\  calls it proprietary, and then tries to keep others from |
_o__)   building on it, is a thief.” —Tim O'Reilly, 2000-01-25 |
Ben Finney
--
http://mail.python.org/mailman/listinfo/python-list