Phlip wrote:
I worded that poorly. None is (AFAIK) the only instance of NoneType, but
I should've clarified the difference. The is operator does not compare
types, it compares instances for identity.
None is typesafe, because it's strongly typed.
Everything in Python is strongly typed. Why
On Jul 8, 12:42 am, Steven D'Aprano steve
+comp.lang.pyt...@pearwood.info wrote:
Phlip wrote:
I worded that poorly. None is (AFAIK) the only instance of NoneType, but
I should've clarified the difference. The is operator does not compare
types, it compares instances for identity.
None is
Phlip wrote:
On Jul 8, 12:42 am, Steven D'Aprano steve
+comp.lang.pyt...@pearwood.info wrote:
Phlip wrote:
I worded that poorly. None is (AFAIK) the only instance of NoneType,
but I should've clarified the difference. The is operator does not
compare types, it compares instances for
Mel mwil...@the-wire.com writes:
def file_to_hash(path, m = hashlib.md5()):
hashlib.md5 *is* called once; that is when the def statement is executed.
Very interesting, I certainly wasn't clear on this. So after that def,
the created hashlib object is in the module's scope and can be
accessed
Anssi Saari a...@sci.fi writes:
Mel mwil...@the-wire.com writes:
def file_to_hash(path, m = hashlib.md5()):
hashlib.md5 *is* called once; that is when the def statement is executed.
Very interesting, I certainly wasn't clear on this. So after that def,
the created hashlib object is in the
On 2011.07.06 06:16 PM, Steven D'Aprano wrote:
Phlip wrote:
Note the fix also avoids comparing to None, which, as usual, is also
icky and less typesafe!
Typesafe? Are you trying to make a joke?
Maybe he has a duck phobia. Maybe he denies the existence of ducks.
Maybe he doesn't like the
On 2011.07.06 06:16 PM, Steven D'Aprano wrote: Phlip wrote:
Note the fix also avoids comparing to None, which, as usual, is also
icky and less typesafe!
Typesafe? Are you trying to make a joke?
No, I was pointing out that passing a type is more ... typesafe.
--
On 2011.07.07 08:11 AM, Phlip wrote:
No, I was pointing out that passing a type is more ... typesafe.
None is a type.
None.__class__
class 'NoneType'
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On Jul 7, 6:24 am, Andrew Berg bahamutzero8...@gmail.com wrote:
On 2011.07.07 08:11 AM, Phlip wrote: No, I was pointing out that passing a
type is more ... typesafe.
None is a type.
I never said it wasn't.
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On 2011.07.07 08:39 AM, Phlip wrote:
On Jul 7, 6:24 am, Andrew Berg bahamutzero8...@gmail.com wrote:
On 2011.07.07 08:11 AM, Phlip wrote: No, I was pointing out that passing a
type is more ... typesafe.
None is a type.
I never said it wasn't.
You are talking about this code, right?
Andrew Berg wrote:
On 2011.07.07 08:39 AM, Phlip wrote:
On Jul 7, 6:24 am, Andrew Berg bahamutzero8...@gmail.com wrote:
On 2011.07.07 08:11 AM, Phlip wrote: No, I was pointing out that
passing a type is more ... typesafe.
None is a type.
I never said it wasn't.
Unfortunately, it
On 2011.07.07 08:46 PM, Steven D'Aprano wrote:
None is not a type, it is an instance.
isinstance(None, type) # is None a type?
False
isinstance(None, type(None)) # is None an instance of None's type?
True
So None is not itself a type, although it *has* a type:
type(None)
type
I worded that poorly. None is (AFAIK) the only instance of NoneType, but
I should've clarified the difference. The is operator does not compare
types, it compares instances for identity.
None is typesafe, because it's strongly typed.
However, what's even MORE X-safe (for various values of X)
On Tue, Jul 5, 2011 at 10:54 PM, Phlip phlip2...@gmail.com wrote:
Pythonistas:
Consider this hashing code:
import hashlib
file = open(path)
m = hashlib.md5()
m.update(file.read())
digest = m.hexdigest()
file.close()
If the file were huge, the file.read() would allocate a big
Am 06.07.2011 07:54 schrieb Phlip:
Pythonistas:
Consider this hashing code:
import hashlib
file = open(path)
m = hashlib.md5()
m.update(file.read())
digest = m.hexdigest()
file.close()
If the file were huge, the file.read() would allocate a big string and
thrash memory.
Phlip phlip2...@gmail.com writes:
If the file were huge, the file.read() would allocate a big string and
thrash memory. (Yes, in 2011 that's still a problem, because these
files could be movies and whatnot.)
I did a crc32 calculator like that and actually ran into some kind of
string length
On Tue, 2011-07-05 at 22:54 -0700, Phlip wrote:
Pythonistas
Consider this hashing code:
import hashlib
file = open(path)
m = hashlib.md5()
m.update(file.read())
digest = m.hexdigest()
file.close()
If the file were huge, the file.read() would allocate a big string and
thrash
wow, tx y'all!
I forgot to mention that hashlib itself is not required; I could also
use Brand X. But y'all agree that blocking up the file in python adds
no overhead to hashing each block in C, so hashlib in a loop it is!
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Tx, all!. But...
For example I use this function to copy a stream and return a SHA512 and
the output streams size:
def write(self, in_handle, out_handle):
m = hashlib.sha512()
data = in_handle.read(4096)
while True:
if not data:
Phlip wrote:
Tx, all!. But...
For example I use this function to copy a stream and return a SHA512 and
the output streams size:
def write(self, in_handle, out_handle):
m = hashlib.sha512()
data = in_handle.read(4096)
while True:
if not data:
break
m.update(data)
- Open the file in binary mode.
I had tried open(path, 'rb') and it didn't change the wrong number.
And I added --binary to my evil md5sum version, and it didn't change
the right number!
Gods bless those legacy hacks that will never die, huh? But I'm using
Ubuntu (inside VMWare, on Win7, on a
Phlip wrote:
- Open the file in binary mode.
I had tried open(path, 'rb') and it didn't change the wrong number.
And I added --binary to my evil md5sum version, and it didn't change
the right number!
Gods bless those legacy hacks that will never die, huh? But I'm using
Ubuntu (inside
def file_to_hash(path, m=None):
if m is None:
m = hashlib.md5()
The first call will give you the correct checksum, the second: not. As the
default md5 instance remembers the state from the previous function call
you'll get the checksum of both files combined.
Ouch. That was it.
Python
- Do the usual dance for default arguments:
def file_to_hash(path, m=None):
if m is None:
m = hashlib.md5()
[instead of
def file_to_hash(path, m = hashlib.md5()):
]
In article b317226a-8008-4177-aaa6-3fdc30125...@e20g2000prf.googlegroups.com
Phlip
On 2011.07.06 12:38 PM, Phlip wrote:
Python sucks. m = md5() looks like an initial assignment, not a
special magic storage mode. Principle of least surprise fail, and
principle of most helpful default behavior fail.
func() = whatever the function returns
func = the function object itself (in
On Jul 6, 11:42 am, Andrew Berg bahamutzero8...@gmail.com wrote:
On 2011.07.06 12:38 PM, Phlip wrote: Python sucks. m = md5() looks like an
initial assignment, not a
special magic storage mode. Principle of least surprise fail, and
principle of most helpful default behavior fail.
func() =
On Wed, Jul 6, 2011 at 3:07 PM, Phlip phlip2...@gmail.com wrote:
On Jul 6, 11:42 am, Andrew Berg bahamutzero8...@gmail.com wrote:
On 2011.07.06 12:38 PM, Phlip wrote: Python sucks. m = md5() looks like an
initial assignment, not a
special magic storage mode. Principle of least surprise fail,
On 2011.07.06 02:07 PM, Phlip wrote:
If I call m = md5() twice, I expect two objects.
You get two objects because you make the function run again. Of course,
the first one is garbage collected if it doesn't have another reference.
m1 = hashlib.md5()
m2 = hashlib.md5()
m1 is m2
False
Are you
Phlip wrote:
If I call m = md5() twice, I expect two objects.
I am now aware that Python bends the definition of call based on
where the line occurs. Principle of least surprise.
Actually, in
def file_to_hash(path, m = hashlib.md5()):
hashlib.md5 *is* called once; that is when the def
On Wed, Jul 6, 2011 at 1:07 PM, Phlip phlip2...@gmail.com wrote:
If I call m = md5() twice, I expect two objects.
I am now aware that Python bends the definition of call based on
where the line occurs. Principle of least surprise.
There is no definition-bending. The code:
def
Phlip wrote:
On 2011.07.06 12:38 PM, Phlip wrote:
Python sucks. m = md5() looks like an initial assignment, not a
special magic storage mode. Principle of least surprise fail, and
principle of most helpful default behavior fail.
If I call m = md5() twice, I expect two objects.
You didn't
On Wednesday, July 6, 2011 12:07:56 PM UTC-7, Phlip wrote:
If I call m = md5() twice, I expect two objects.
I am now aware that Python bends the definition of call based on
where the line occurs. Principle of least surprise.
Phlip:
We already know about this violation of the least surprise
On Jul 6, 1:25 pm, Carl Banks pavlovevide...@gmail.com wrote:
We already know about this violation of the least surprise principle; most of
us acknowledge it as small blip in an otherwise straightforward and clean
language.
Here's the production code we're going with - thanks again all:
Phlip wrote:
Note the fix also avoids comparing to None, which, as usual, is also
icky and less typesafe!
Typesafe? Are you trying to make a joke?
--
Steven
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