Re: Input() in Python3
Westley Martínez wrote:
On Fri, Apr 22, 2011 at 10:08:20AM -0400, Mel wrote:
[ ... ]
But sys.exit() doesn't return a string. My fave is
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import sys
a = int (input ('enter a number '))
enter a number sys.setrecursionlimit(1)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
[ ... ]
What?
I guess sys.setrecursionlimit was meant to be called with a large number.
Calling it with a small one roadblocks the interpreter. Luckily, there can
be just enough room to call setrecursionlimit again with something
reasonable to get it all back. Not enough room for `eval
(sys.setrecursionlimit (2000)`, though.
Mel.
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Re: Input() in Python3
Hey! Try to use like this: http://sprunge.us/RcYb change values for understanding code. Good ideas guys! --- Jayme Proni Filho Skype: jaymeproni Twitter: @jaymeproni Phone: +55 - 17 - 3631 - 6576 Mobile: +55 - 17 - 9605 - 3560 e-Mail: jaymeproni at yahoo dot com dot br --- -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Fri, Apr 22, 2011 at 10:08:20AM -0400, Mel wrote:
Westley Martínez wrote:
On Fri, Apr 22, 2011 at 04:49:19PM +1000, Chris Angelico wrote:
U NO. NO NO NO. What if someone enters os.exit() as their
number? You shouldn't eval() unchecked user input!
Chris Angelico
Right, there's no way to check you're getting a number, however using:
a = int(input('enter a number ')) # use float() for floats
will raise an exception if it can't convert the string.
But sys.exit() doesn't return a string. My fave is
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import sys
a = int (input ('enter a number '))
enter a number sys.setrecursionlimit(1)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python object
int (0)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python object
Mel.
What?
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Re: Input() in Python3
Chris Rebert wrote: Well, it pretty much*was* totally removed; it was prone to misuse and had very few legitimate uses. It's just that raw_input() also got renamed simultaneously. What were you using it for? There are often much better alternatives. For the purpose pretty much described in PEP 3111... education. Teaching new programmers input, control, arithmetic, logic, and output works best with simple built-ins. IMHO I want to teach young folks how to get stuff into their simple programs, crank on them a bit, and spit out the results... without having to teach them imports, libraries, etc. Keep in mind that some of this stuff is very simple (say trivial) and is being used to provide a way to get the data 'they are expecting' into the program easily, with a prompt. This was the great concept in BASIC, and REXX, and others. The C language broke with this concept by declaring that the language does not provide I/O ... only in the standard library, as functions! The beauty of Python (as I've noted before) is that it can be used in an uber-sophisticated way... AND it can also be taught to children! Having thought a little more about that, I suppose that I agree that input() should return a raw string. After all, the students aren't really entering numbers are they?? They are entering strings of characters that need to be converted into numbers... easily explained... I was just surprised to find that issue so hotly debated... again, why remove something that works. The wisdom was to use a system call instead, right? kind regards, m harris -- http://mail.python.org/mailman/listinfo/python-list
Input() in Python3
My interactive scripts are giving errors on the input(). I discovered another fairly significant change in Python3, as discussed in PEP 3111. I was a little flabbergasted to discover that input() was proposed to be removed 'totally' from 3000. Of course I agree with PEP 3111 and am thankful that input() is still a built-in. doh. The problem is that the behavior was significantly changed, again, causing existing code to break un-necessarily. So, input() used to be equivalent to: eval(raw_input(prompt)) -- value now we get this for input(): raw_input(prompt) -- string I'm not whining or anything, just wondering why? Could someone enlighten me please? Anyway, it looks like the best fix for 2.x -- 3.x code changes: change:a = input(enter a number ) to:a = eval(input(enter a number )) Again, this is just another example where leaving the advertised interface alone would have made more sense... unless of course, I'm missing something important here. kind regards, m harris -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Fri, Apr 22, 2011 at 4:22 PM, harrismh777 harrismh...@charter.net wrote: now we get this for input(): raw_input(prompt) -- string I would have to say that the 2.x behaviour of input() is a mistake that's being corrected in 3.x. With a simple name like input(), it should do something simple and straightforward - not eval() the expression. to: a = eval(input(enter a number )) U NO. NO NO NO. What if someone enters os.exit() as their number? You shouldn't eval() unchecked user input! Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Fri, Apr 22, 2011 at 4:49 PM, Chris Angelico ros...@gmail.com wrote: U NO. NO NO NO. What if someone enters os.exit() as their number? You shouldn't eval() unchecked user input! Whoops, I meant sys.exit() - but you probably knew that already. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Thu, Apr 21, 2011 at 11:22 PM, harrismh777 harrismh...@charter.net wrote: My interactive scripts are giving errors on the input(). I discovered another fairly significant change in Python3, as discussed in PEP 3111. I was a little flabbergasted to discover that input() was proposed to be removed 'totally' from 3000. Of course I agree with PEP 3111 and am thankful that input() is still a built-in. doh. Well, it pretty much *was* totally removed; it was prone to misuse and had very few legitimate uses. It's just that raw_input() also got renamed simultaneously. What were you using it for? There are often much better alternatives. The problem is that the behavior was significantly changed, again, causing existing code to break un-necessarily. Python 3 has many unnecessary backwards-incompatible changes; the Python devs have made this abundantly clear and one should be aware of this before going into Python 3. And again, I don't think a behavior change is the best way to conceptualize this, although from a user perspective, there indeed isn't much difference between a behavior change and a simultaneous removal and renaming. So, input() used to be equivalent to: eval(raw_input(prompt)) -- value now we get this for input(): raw_input(prompt) -- string I'm not whining or anything, just wondering why? Could someone enlighten me please? Anyway, it looks like the best fix for 2.x -- 3.x code changes: change: a = input(enter a number ) to: a = eval(input(enter a number )) Did you run your scripts through the 2to3 converter tool? This is one of the many changes it can apply automatically. Again, this is just another example where leaving the advertised interface alone would have made more sense... unless of course, I'm missing something important here. input() was rarely used correctly and is quite trivially replaced. raw_input() was used much more frequently, but was a bit awkwardly named. Python 3 made use of its backwards-incompatible status to rectify both of these problems at once. Writing correct code will be now easier for newbies. If you're porting stuff to Python 3, using 2to3 and reading the summary of changes from 2.x are absolute necessities. Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Fri, Apr 22, 2011 at 04:49:19PM +1000, Chris Angelico wrote:
On Fri, Apr 22, 2011 at 4:22 PM, harrismh777 harrismh...@charter.net wrote:
now we get this for input():
raw_input(prompt) -- string
I would have to say that the 2.x behaviour of input() is a mistake
that's being corrected in 3.x. With a simple name like input(), it
should do something simple and straightforward - not eval() the
expression.
to: a = eval(input(enter a number ))
U NO. NO NO NO. What if someone enters os.exit() as their
number? You shouldn't eval() unchecked user input!
Chris Angelico
Right, there's no way to check you're getting a number, however using:
a = int(input('enter a number ')) # use float() for floats
will raise an exception if it can't convert the string.
--
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Re: Input() in Python3
Westley Martínez wrote:
On Fri, Apr 22, 2011 at 04:49:19PM +1000, Chris Angelico wrote:
U NO. NO NO NO. What if someone enters os.exit() as their
number? You shouldn't eval() unchecked user input!
Chris Angelico
Right, there's no way to check you're getting a number, however using:
a = int(input('enter a number ')) # use float() for floats
will raise an exception if it can't convert the string.
But sys.exit() doesn't return a string. My fave is
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import sys
a = int (input ('enter a number '))
enter a number sys.setrecursionlimit(1)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python object
int (0)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python object
Mel.
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Re: Input() in Python3
On Apr 22, 2011 10:12 AM, Mel mwil...@the-wire.com wrote:
Westley Martínez wrote:
On Fri, Apr 22, 2011 at 04:49:19PM +1000, Chris Angelico wrote:
U NO. NO NO NO. What if someone enters os.exit() as their
number? You shouldn't eval() unchecked user input!
Chris Angelico
Right, there's no way to check you're getting a number, however using:
a = int(input('enter a number ')) # use float() for floats
will raise an exception if it can't convert the string.
But sys.exit() doesn't return a string. My fave is
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type help, copyright, credits or license for more information.
import sys
a = int (input ('enter a number '))
enter a number sys.setrecursionlimit(1)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python
object
int (0)
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Exception RuntimeError: 'maximum recursion depth exceeded while calling a
Python object' in type 'exceptions.RuntimeError' ignored
Error in sys.excepthook:
RuntimeError: maximum recursion depth exceeded
Original exception was:
Traceback (most recent call last):
File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded while calling a Python
object
Mel.
We're talking about python 3, not python 2. If you're using python 2, the
equivalent code would be int(raw_input()) and that isn't vulnerable to this
sort of thing.
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Re: Input() in Python3
On Sat, Apr 23, 2011 at 12:08 AM, Mel mwil...@the-wire.com wrote: But sys.exit() doesn't return a string. My fave is It doesn't return _at all_. Boom, process terminated. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Sat, 23 Apr 2011 06:25:51 +1000, Chris Angelico wrote: On Sat, Apr 23, 2011 at 12:08 AM, Mel mwil...@the-wire.com wrote: But sys.exit() doesn't return a string. My fave is It doesn't return _at all_. Boom, process terminated. Technically it raises an exception, which can then be caught by the usual exception-handling mechanism. So it's not quite Boom. try: ... sys.exit(42) ... except SystemExit as e: ... print(e.code) ... 42 -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Input() in Python3
On Sat, Apr 23, 2011 at 9:55 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Sat, 23 Apr 2011 06:25:51 +1000, Chris Angelico wrote: On Sat, Apr 23, 2011 at 12:08 AM, Mel mwil...@the-wire.com wrote: But sys.exit() doesn't return a string. My fave is It doesn't return _at all_. Boom, process terminated. Technically it raises an exception, which can then be caught by the usual exception-handling mechanism. So it's not quite Boom. Sure, but it still doesn't return anything. In any case, it's not something you want to eval casually in the middle of asking the user for an integer. Chris Angelico -- http://mail.python.org/mailman/listinfo/python-list
