[Numpy-discussion] A bug in loadtxt and how to convert a string array (hex data) to decimal?

[Ryan May]

frank wang wrote:
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> 
> 
> Hi, All,
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>  
> 
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> I have found a bug in the loadtxt function. Here is the example. The 
> file name is test.txt and contains:
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> "Thist is test"
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> 3FF 3fE
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> 3Ef 3e8
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> 3Df 3d9
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> 3cF 3c7
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>  
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> In the Python 2.5.2, I type:
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> test=loadtxt('test.txt',comments='"',dtype='string',converters={0:lambda 
> s:int(s,16)})
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>  
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> test will contain
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>  
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> array([['102', '3fE'],
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>        ['100', '3e8'],
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>        ['991', '3d9'],
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>        ['975', '3c7']],
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>       dtype='|S3')
> 

It's because of how numpy handles strings arrays (which I admit I don't 
understand very well.)  Basically, it's converting the numbers properly, 
but truncating them to 3 characters.  Try this, which just forces it to 
expand to strings 4 characters wide:
					test=loadtxt('test.txt',comments='"',dtype='|S4',converters={0:lambda
	s:int(s,16)})

HTH,

Ryan

-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma