[issue32112] Should uuid.UUID() accept another UUID() instance?

[Irit Katriel]

Change by Irit Katriel :


--
resolution:  -> rejected
stage:  -> resolved
status: open -> closed
type:  -> enhancement

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32112] Should uuid.UUID() accept another UUID() instance?

[Irit Katriel]

Irit Katriel  added the comment:

I agree with Serhiy that there needs to be a reason for adding this to a class 
constructor.

In the case of int, this is to implement conversion - it's not accepting int, 
it's accepting any number (it would be weird of int(3.4) worked and int(3) 
didn't).  Similarly, complex constructor accepts numbers.

In the case of tuple, bytes, bytearray - the constructor accepts any iterable, 
again in order to implement type conversion.


So it's not random - these constructors accept objects of the same type because 
they accept params of a more generic type, in order to provide type conversion 
functionality.

What functionality would we gain from increasing the API surface of the UUID 
constructor as you suggest?

--
nosy: +iritkatriel

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32112] Should uuid.UUID() accept another UUID() instance?

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Growing the size of the code and the documentation, complicating the mental 
model, slowing down all other cases, the risk of introducing bugs. This is the 
cost that we should pay for adding a new feature. The benefit of adding a 
feature should be larger than this cost. I'm not sure this is a case. But if 
you think it is worth, you can add it.

Note that by adding this feature you can open a can of worms and will need to 
add support of time(time), date(date), namedtuple(namedtuple), etc for the same 
reason, because some database drivers already do mapping for you.

--

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32112] Should uuid.UUID() accept another UUID() instance?

[Éric Araujo]

Éric Araujo  added the comment:

I don’t see a downside in accepting the feature request here.

Maybe ask on python-ideas to get more feedback?

--
nosy: +eric.araujo

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32112] Should uuid.UUID() accept another UUID() instance?

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

Not always the constructor accept an instance of the same class. I'm sure that 
this is not true in the majority of cases.

The constructor of int accepts an instance of int and the constructor of tuple 
accepts an instance of tuple because the constructor of int accepts an 
arbitrary real number, and the constructor of tuple accepts an arbitrary 
iterable, and int and tuple are a real number and an iterable correspondingly. 
There is no reason to forbid accepting an instance of the same class in these 
cases.

In contrary, the UUID constructor accepts a hexadecimal string, but UUID itself 
is not a hexadecimal string. Similarly the range constructor doesn't accept a 
range instance, and the file constructor doesn't accept a file instance.

>>> range(range(3))
Traceback (most recent call last):
  File "", line 1, in 
TypeError: 'range' object cannot be interpreted as an integer
>>> io.FileIO(io.FileIO('/dev/null'))
Traceback (most recent call last):
  File "", line 1, in 
TypeError: expected str, bytes or os.PathLike object, not _io.FileIO

For converting an existing UUID instance to UUID you can can first convert it 
to str:

newvalue = uuid.UUID(str(oldvalue))

Or better avoid the conversion at all.

if isisnstance(oldvalue, uuid.UUID):
newvalue = oldvalue
else:
newvalue = uuid.UUID(oldvalue)

--
nosy: +serhiy.storchaka

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32112] Should uuid.UUID() accept another UUID() instance?

[Antti Haapala]

Antti Haapala  added the comment:

I've been hit by this too, in similar contexts, and several times. It is really 
annoying that it is easier to coerce an UUID or UUID-string to a string than to 
coerce to a UUID. Usually when the copy semantics are clear and the class is 
plain old data, Python lets you execute the constructor with an instance of the 
same class:

>>> bytes(bytes())
b''
>>> bytearray(bytearray())
bytearray(b'')
>>> int(int())
0
>>> complex(complex())
0j
>>> tuple(tuple())
()

I don't to see why this shouldn't be true with UUID as well.

--
nosy: +ztane

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com

[issue32112] Should uuid.UUID() accept another UUID() instance?

[Martijn Pieters]

New submission from Martijn Pieters :

When someone accidentally passes in an existing uuid.UUID() instance into 
uuid.UUID(), an attribute error is thrown because it is not a hex string:

>>> import uuid
>>> value = uuid.uuid4()
>>> uuid.UUID(value)
Traceback (most recent call last):
  File "", line 1, in 
  File 
"/Users/mjpieters/Development/Library/buildout.python/parts/opt/lib/python2.7/uuid.py",
 line 133, in __init__
hex = hex.replace('urn:', '').replace('uuid:', '')
AttributeError: 'UUID' object has no attribute 'replace'

This happened in the Stack Overflow question at 
https://stackoverflow.com/q/47429929/100297, because the code there didn't take 
into account that some database drivers may already have mapped the PostgreSQL 
UUID column to a Python uuid.UUID() object.

The fix could be as simple as:

if hex is not None:
if isinstance(hex, uuid.UUID):
int = hex.int
else:
hex = hex.replace('urn:', '').replace('uuid:', '')
hex = hex.strip('{}').replace('-', '')
if len(hex) != 32:
raise ValueError('badly formed hexadecimal UUID string')
int = int_(hex, 16)

Or we could add a uuid=None keyword argument, and use 

if hex is not None:
if isinstance(hex, uuid.UUID):
uuid = hex
else:
hex = hex.replace('urn:', '').replace('uuid:', '')
hex = hex.strip('{}').replace('-', '')
if len(hex) != 32:
raise ValueError('badly formed hexadecimal UUID string')
int = int_(hex, 16)
if uuid is not None:
int = uuid.int

--
messages: 306719
nosy: mjpieters
priority: normal
severity: normal
status: open
title: Should uuid.UUID() accept another UUID() instance?

___
Python tracker 

___
___
Python-bugs-list mailing list
Unsubscribe: 
https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com