Re: Minor bug in tempfile module (possibly __doc__ error)

2007-05-10 Thread James T. Dennis 
Dennis Lee Bieber [EMAIL PROTECTED] wrote:
 On Wed, 09 May 2007 06:50:38 -, James T. Dennis
 [EMAIL PROTECTED] declaimed the following in comp.lang.python:


  In fact I realized, after reading through tempfile.py in /usr/lib/...
  that the following also doesn't work like I'd expect:

No idea of the tempfile problem, but...
 
   # foo.py
   tst = foo
   def getTst(arg):
   return foo-%s % arg

This return is using a literal foo-. Change it to

return %s-%s % (tst, arg)

Sorry that was a retyping bug in my posting ... not in
my sample code which was on another system.

 and try again.

Try it yourself.  As I said ... the value of tst in your
name space will be changed, but the value returned by functions
in the imported module will still use the old value!


-- 
Jim Dennis,
Starshine: Signed, Sealed, Delivered

-- 
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Re: Minor bug in tempfile module (possibly __doc__ error)

2007-05-10 Thread James T. Dennis 
Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote:
 In [EMAIL PROTECTED], James T. Dennis wrote:

  Tonight I discovered something odd in the __doc__ for tempfile
  as shipped with Python 2.4.4 and 2.5: it says:
 
   This module also provides some data items to the user:
 
 TMP_MAX  - maximum number of names that will be tried before
giving up.
 template - the default prefix for all temporary names.
You may change this to control the default prefix.
 
  ... which would lead one to think that the following code would work:
 
import tempfile
tempfile.template = 'mytest'
tf = tempfile.NamedTemporaryFile()
  tf.name
   '/tmp/mytest-XX'
 
  It doesn't.

 The source says:

 __all__ = [
NamedTemporaryFile, TemporaryFile, # high level safe interfaces
mkstemp, mkdtemp,  # low level safe interfaces
mktemp,  # deprecated unsafe interface
TMP_MAX, gettempprefix,# constants
tempdir, gettempdir
   ]

 Maybe the doc should be clearer in saying constants too.

  Secondly, the author(s) of the tempfile module apparently didn't
  understand this either.  And no one else even noticed that the __doc__
  is wrong (or at least misleading -- since the only way I can see to
  change tempfile.template is to edit the .py file!

 You can change it by simply assigning to the name:

 In [15]: tempfile.template = 'spam'

 In [16]: tempfile.template
 Out[16]: 'spam'

I know you can change it.  But changing it in your namespace
doesn't change the results returned by the functions called
from the module.

 If you want to change the outcome of the functions and objects then simply
 give the prefix as argument.

I know how to provide the prefix arguments and that was
never the issue.

The issue was twofold:

The docs are wrong (or at least confusing/misleading)

I don't quite understand how this name/variable in
my namespace (__main__) is able to change the value
while the functions in the module still hold the old
value.

-- 
Jim Dennis,
Starshine: Signed, Sealed, Delivered

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Re: Minor bug in tempfile module (possibly __doc__ error)

2007-05-10 Thread Marc 'BlackJack' Rintsch 
In [EMAIL PROTECTED], James T. Dennis wrote:

 Marc 'BlackJack' Rintsch [EMAIL PROTECTED] wrote:
 In [EMAIL PROTECTED], James T. Dennis wrote:
 
 You can change it by simply assigning to the name:
 
 In [15]: tempfile.template = 'spam'
 
 In [16]: tempfile.template
 Out[16]: 'spam'
 
   I know you can change it.  But changing it in your namespace
   doesn't change the results returned by the functions called
   from the module.

I'm not changing it in my namespace but in the namespace of the `tempfile`
module.

   I don't quite understand how this name/variable in
   my namespace (__main__) is able to change the value
   while the functions in the module still hold the old
   value.

Default arguments are evaluated *once* when the ``def`` is executed and
not at every function call.

Ciao,
Marc 'BlackJack' Rintsch
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Re: Minor bug in tempfile module (possibly __doc__ error)

2007-05-10 Thread Marc Christiansen 
James T. Dennis [EMAIL PROTECTED] scribis:
 In fact I realized, after reading through tempfile.py in /usr/lib/...
 that the following also doesn't work like I'd expect:
 
# foo.py
tst = foo
def getTst(arg):
If I change this line:
return foo-%s % arg
to:
 return %s-%s % (tst, arg)

# bar.py
import foo
foo.tst = bar
print foo.getTst(testing)

foo-testing - NOT bar-testing
Then python bar.py prints bar-testing.

0:[EMAIL PROTECTED]:/tmp cat foo.py
tst = foo
def getTst(arg):
return %s-%s % (tst,arg)
0:[EMAIL PROTECTED]:/tmp cat bar.py
import foo
foo.tst = bar
print foo.getTst(testing)
0:[EMAIL PROTECTED]:/tmp python bar.py 
bar-testing

And regarding the tempfile.template problem, this looks like a bug.
Because all functions in tempfile taking a prefix argument use def
function(... , prefix=template, ...), only the value of template at
import time matters. 

Adiaŭ, Marc
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Re: Minor bug in tempfile module (possibly __doc__ error)

2007-05-10 Thread James T. Dennis 
Marc Christiansen [EMAIL PROTECTED] wrote:
 James T. Dennis [EMAIL PROTECTED] scribis:
 In fact I realized, after reading through tempfile.py in /usr/lib/...
 that the following also doesn't work like I'd expect:

# foo.py
tst = foo
def getTst(arg):
 If I change this line:
return foo-%s % arg
 to:
 return %s-%s % (tst, arg)

# bar.py
import foo
foo.tst = bar
print foo.getTst(testing)

foo-testing - NOT bar-testing
 Then python bar.py prints bar-testing.

0:[EMAIL PROTECTED]:/tmp cat foo.py
tst = foo
def getTst(arg):
return %s-%s % (tst,arg)
0:[EMAIL PROTECTED]:/tmp cat bar.py
import foo
foo.tst = bar
print foo.getTst(testing)
0:[EMAIL PROTECTED]:/tmp python bar.py 
bar-testing

 And regarding the tempfile.template problem, this looks like a bug.
 Because all functions in tempfile taking a prefix argument use def
 function(... , prefix=template, ...), only the value of template at
 import time matters. 

 Adia?, Marc

 I suppose my real sample code was def getTst(arg=tst):
 
 Oddly I've never come across that (the fact that defaulted arguments are
 evaluated during function definition) in my own coding and I guess there
 are two reasons for that: I try to avoid global variables and I usually
 use defaulted variables of the form:

def (foo=None):
if foo is None:
foo = self.default_foo

 


-- 
Jim Dennis,
Starshine: Signed, Sealed, Delivered

-- 
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Minor bug in tempfile module (possibly __doc__ error)

2007-05-09 Thread James T. Dennis 


 Tonight I discovered something odd in the __doc__ for tempfile
 as shipped with Python 2.4.4 and 2.5: it says:

This module also provides some data items to the user:

  TMP_MAX  - maximum number of names that will be tried before
 giving up.
  template - the default prefix for all temporary names.
 You may change this to control the default prefix.

 ... which would lead one to think that the following code would work:

 import tempfile
 tempfile.template = 'mytest'
 tf = tempfile.NamedTemporaryFile()
 tf.name
'/tmp/mytest-XX'

 It doesn't.

 In fact I realized, after reading through tempfile.py in /usr/lib/...
 that the following also doesn't work like I'd expect:

# foo.py
tst = foo
def getTst(arg):
return foo-%s % arg


# bar.py
import foo
foo.tst = bar
print foo.getTst(testing)

foo-testing - NOT bar-testing

 Now I would feel like a real idiot if I'd come across that in the
 foo/bar case here ... because I clearly don't understand quite *why*
 I can't monkey patch this value.  I would ... but I don't.

 First, I wouldn't have written code like this foo/bar stuff; except
 to test my hypothesis about why changes to tempfile.template don't
 actually affect the values seen by functions in the tempfile namespace.

 Secondly, the author(s) of the tempfile module apparently didn't
 understand this either.  And no one else even noticed that the __doc__
 is wrong (or at least misleading -- since the only way I can see to
 change tempfile.template is to edit the .py file!

 So, I don't feel like an idiot.  But I am curious ...

 ... why can't I change that value in that other namespace?  Is it
 a closure?  (Or like a closure?)  Where is this particular aspect
 of the import/namespace semantics documented?


-- 
Jim Dennis,
Starshine: Signed, Sealed, Delivered

-- 
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Re: Minor bug in tempfile module (possibly __doc__ error)

2007-05-09 Thread Marc 'BlackJack' Rintsch 
In [EMAIL PROTECTED], James T. Dennis wrote:

  Tonight I discovered something odd in the __doc__ for tempfile
  as shipped with Python 2.4.4 and 2.5: it says:
 
   This module also provides some data items to the user:
 
 TMP_MAX  - maximum number of names that will be tried before
giving up.
 template - the default prefix for all temporary names.
You may change this to control the default prefix.
 
  ... which would lead one to think that the following code would work:
 
import tempfile
tempfile.template = 'mytest'
tf = tempfile.NamedTemporaryFile()
  tf.name
   '/tmp/mytest-XX'
 
  It doesn't.

The source says:

__all__ = [
NamedTemporaryFile, TemporaryFile, # high level safe interfaces
mkstemp, mkdtemp,  # low level safe interfaces
mktemp,  # deprecated unsafe interface
TMP_MAX, gettempprefix,# constants
tempdir, gettempdir
   ]

Maybe the doc should be clearer in saying constants too.

  Secondly, the author(s) of the tempfile module apparently didn't
  understand this either.  And no one else even noticed that the __doc__
  is wrong (or at least misleading -- since the only way I can see to
  change tempfile.template is to edit the .py file!

You can change it by simply assigning to the name:

In [15]: tempfile.template = 'spam'

In [16]: tempfile.template
Out[16]: 'spam'

If you want to change the outcome of the functions and objects then simply
give the prefix as argument.

In [21]: tempfile.mktemp(prefix='eggs')
Out[21]: '/tmp/eggsBqiqZD'

In [22]: a = tempfile.NamedTemporaryFile(prefix='eric')

In [23]: a.name
Out[23]: '/tmp/ericHcns14'

  ... why can't I change that value in that other namespace?  Is it
  a closure?  (Or like a closure?)  Where is this particular aspect
  of the import/namespace semantics documented?

You *can* change it, but it is not used by the code in that module.

Ciao,
Marc 'BlackJack' Rintsch
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