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

2008-09-18 Thread Ryan May 
frank wang wrote:
 
 
 
 Hi, All,
 
 
  
 
 
 I have found a bug in the loadtxt function. Here is the example. The 
 file name is test.txt and contains:
 
 
 Thist is test
 
 
 3FF 3fE
 
 
 3Ef 3e8
 
 
 3Df 3d9
 
 
 3cF 3c7
 
 
  
 
 
 In the Python 2.5.2, I type:
 
 
  
 
 
 test=loadtxt('test.txt',comments='',dtype='string',converters={0:lambda 
 s:int(s,16)})
 
 
  
 
 
 test will contain
 
 
  
 
 
 array([['102', '3fE'],
 
 
['100', '3e8'],
 
 
['991', '3d9'],
 
 
['975', '3c7']],
 
 
   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
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Re: [Numpy-discussion] A bug in loadtxt and how to convert a string array (hex data) to decimal?

2008-09-18 Thread frank wang 

Hi, Ryan,
 
Thank you very much. It solves my problem. I have struggled with this for long 
time.
 
Frank Date: Thu, 18 Sep 2008 16:39:47 -0500 From: [EMAIL PROTECTED] To: 
numpy-discussion@scipy.org Subject: Re: [Numpy-discussion] A bug in loadtxt 
and how to convert a string array (hex data) to decimal?  frank wang wrote: 
   Hi, All,I have found a bug in the loadtxt 
function. Here is the example. The   file name is test.txt and contains:   
   Thist is test  3FF 3fE  3Ef 3e8  3Df 3d9 
 3cF 3c7In the Python 2.5.2, I type: 
   
test=loadtxt('test.txt',comments='',dtype='string',converters={0:lambda   
s:int(s,16)})test will contain
array([['102', '3fE'],  ['100', '3e8'],  ['991', '3d9'],  
['975', '3c7']],  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 
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