Hello,
first question
In [117]: cmp("ABC",['A','B','C'])
Out[117]: 1
against what part of the list is the string "ABC" compared?
second question
In [119]: class X(object):
.....: pass
.....:
In [120]: X() < X()
Out[120]: True
In [121]: X() < X()
Out[121]: False
In [122]: X() < X()
Out[122]: True
In [123]: X() < X()
Out[123]: True
In [124]: X() < X()
Out[124]: False
class X does not implement < and cmp
what is this comparision is based on?
third question
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
how does python handle heterogenous items in the list
in this case?
first I assumed that cmp function used in sort
is based on len, when the items are sequences, but this is wrong
Regards, Daniel 4 1513
Schüle Daniel <uv**@rz.uni-karlsruhe.dewrites:
Hello,
first question
In [117]: cmp("ABC",['A','B','C'])
Out[117]: 1
against what part of the list is the string "ABC" compared?
Why "part"? There are two objects; they are compared to each other.
How this comparison is implemented is a matter handled by the class of
each object.
second question
In [119]: class X(object):
.....: pass
.....:
In [120]: X() < X()
[... differing results ...]
class X does not implement < and cmp
what is this comparision is based on?
Classes can implement various functions to allow comparisons to work:
<URL:http://docs.python.org/ref/customization.html#l2h-187>
In the absence of those, the comparison's result is (I believe)
implementation-dependent -- which means, "don't rely on any particular
behaviour".
third question
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
>>sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
File "<stdin>", line 1
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
^
SyntaxError: invalid syntax
Care to give an actual example?
--
\ "I went to the hardware store and bought some used paint. It |
`\ was in the shape of a house." -- Steven Wright |
_o__) |
Ben Finney
Schüle Daniel schrieb:
first question
In [117]: cmp("ABC",['A','B','C'])
Out[117]: 1
against what part of the list is the string "ABC" compared?
The names of the types are compared:
pycmp("string", "list")
1
second question
In [119]: class X(object):
.....: pass
.....:
In [120]: X() < X()
Out[120]: True
what is this comparision is based on?
The addresses of the objects, in main memory.
third question
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
how does python handle heterogenous items in the list
in this case?
pair-by-pair. It is quite difficult to impose a total
order on all objects; this will go away in Python 3.
Regards,
Martin
Schüle Daniel wrote:
first question
In [117]: cmp("ABC",['A','B','C'])
Out[117]: 1
against what part of the list is the string "ABC" compared?
http://docs.python.org/lib/comparisons.html
"Objects of different types, except different numeric types and
different string types, never compare equal; such objects are
ordered consistently but arbitrarily (so that sorting a hetero-
geneous array yields a consistent result)"
class X does not implement < and cmp
what is this comparision is based on?
"objects of the same types that don't support proper comparison
are ordered by their address"
third question
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
how does python handle heterogenous items in the list
in this case?
"Objects of different types, except different numeric types and
different string types, never compare equal; such objects are
ordered consistently but arbitrarily (so that sorting a hetero-
geneous array yields a consistent result)"
first I assumed
no, first you assumed that this wasn't documented.
</F>
"Ben Finney" <bi****************@benfinney.id.auwrote:
To: <py*********@python.org>
Sent: Thursday, October 26, 2006 4:44 AM
Subject: Re: basic questions on cmp, < and sort
Schüle Daniel <uv**@rz.uni-karlsruhe.dewrites:
8<-------------------------------------------
third question
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
>>sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
File "<stdin>", line 1
sort([[1,2,3],["ABC"],['Z','A'], X(), 4)
^
SyntaxError: invalid syntax
needs a closing ']' to make the list a list.....
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