['a', 'b'][True] results 'b' But how?

[kath]

Hi,

Can any one please tell me how is the following code is working?
['a','b'] is a list of string, and [True] is list of boolean value.
How is it making effect?
code Python24

 ['a','b] [True]
'b'
 ['a','b'] [False]
'a'
 ['a','b']['some_string' == r'some_string']
'b'
 ['a','b']['some_string' == r'somestring']
'a'

code


Thanks in advance,
regards,
kath.

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Re: ['a', 'b'][True] results 'b' But how?

[Kelvie Wong]

In this case, [True] and [False] are not lists, rather you're
accessing the items of the list with the index True or False, as per
the following example:

 a_list = ['a', 'b']
 a_list[True]
'b'
 a_list[False]
'a'

This happens because the __getitem__ method takes its argument (which
in this case is True or False) and casts it into an integer:

 int(True)
1
 int(False)
0

So thus it follows logically that since:
 a_list[1]
'b'
 a_list[0]
'a'

a_list[True] and a_list[False] must be its first and zeroth  indexed
members, respectively.


On 7/4/07, kath [EMAIL PROTECTED] wrote:
 Hi,

 Can any one please tell me how is the following code is working?
 ['a','b'] is a list of string, and [True] is list of boolean value.
 How is it making effect?
 code Python24

  ['a','b] [True]
 'b'
  ['a','b'] [False]
 'a'
  ['a','b']['some_string' == r'some_string']
 'b'
  ['a','b']['some_string' == r'somestring']
 'a'

 code


 Thanks in advance,
 regards,
 kath.

 --
 http://mail.python.org/mailman/listinfo/python-list



-- 
Kelvie
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Re: ['a', 'b'][True] results 'b' But how?

[Robert Bauck Hamar]

kath wrote:

 Hi,
 
 Can any one please tell me how is the following code is working?
 ['a','b'] is a list of string

Yes.

 and [True] is list of boolean value. 

No. It's the subscription operator applied to the list of strings.
a = ['a', 'b']
a[True]
may be clearer.

 How is it making effect?

 int(True)
1
 int(False)
0
 isinstance(True, int)
True
 bool.__bases__
(type 'int',)

 code Python24
 
 ['a','b] [True]
 'b'
 ['a','b'] [False]
 'a'
 ['a','b']['some_string' == r'some_string']
 'b'
 ['a','b']['some_string' == r'somestring']
 'a'
 
 code

-- 
rbh
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Re: ['a', 'b'][True] results 'b' But how?

[rishi pathak]

True stands for 1 and False stands for 0
so list[True] is equivalent to list[1]
and list[False] is equivalent to list[0]

On 7/5/07, kath [EMAIL PROTECTED] wrote:


Hi,

Can any one please tell me how is the following code is working?
['a','b'] is a list of string, and [True] is list of boolean value.
How is it making effect?
code Python24

 ['a','b] [True]
'b'
 ['a','b'] [False]
'a'
 ['a','b']['some_string' == r'some_string']
'b'
 ['a','b']['some_string' == r'somestring']
'a'

code


Thanks in advance,
regards,
kath.

--
http://mail.python.org/mailman/listinfo/python-list





--
Regards--
Rishi Pathak
National PARAM Supercomputing Facility
Center for Development of Advanced Computing(C-DAC)
Pune University Campus,Ganesh Khind Road
Pune-Maharastra
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