> Thanks for the reply. I've tried your suggestion and am still getting
> an error (posted below code). Since my posting, I've also added the
> code to convert the numpy array to a list. My complete script is:
>
> -----
> # -*- coding: utf-8 -*-
>
> import pupynere
> import os
> import csv
> import glob
>
> def get_file_details(filename):
> sub1='3B42.'
> sub2='.nc'
> extract=filename.split(sub1)[-1].split(sub2)[0]
> elements=extract.split('.')
> ure={'0':'00:00:00',
> '3':'03:00:00',
> '6':'06:00:00',
> '9':'09:00:00',
> '12':'12:00:00',
> '15':'15:00:00',
> '18':'18:00:00',
> '21':'21:00:00'}
> date='20'+elements[0]
> time=ure[elements[1]]
> return[date,time]
>
> def get_rain_data(filename):
> # trmm blocks covering study area
> rows=[87,86,85,86]
> cols=[833,833,833,834]
>
> # open file
> file = pupynere.netcdf_file(filename,'r')
> # read data
> precipitation=file.variables['precipitation']
> # close file file.close()
>
> # read values for blocks of interest
> precip=precipitation[rows,cols]
> # convert numpy array to list
> precip=precip.tolist()
> return[precip]
You just converted precip to a list (precip.tolist()), then, in the next line,
you're turning that into a list.
So you get a list within a list, which results in the errors below. Exactly as
you hinted at yourself below.
(In fact, if you now would do
>>> data[0]
[0.0, 0.0, 0.0, 0.0]
because this is the representation (repr). Not the 0.0 you previously showed.)
Once you get rid of the extra list, you can use either float(data[0]) and %f
(if you require detailed formatting) or just simply %s, as Alan suggested.
Evert
>
>
> # get list of .nc files in folder
> os.chdir('F:\\Hanlie\\UCT\\M.Sc\\Data\\TRMM\\2000\\02_Februarie')
> filepattern='*.nc'
> nc_files=glob.glob(filepattern)
>
> # write to CSV-file with spaces as delimiter
> csv.register_dialect('spaces', delimiter=' ')
> outfilename="trmm_c83a_feb2000.txt"
> out_text=open(outfilename, 'wb')
> writer = csv.writer(out_text,dialect='spaces')
>
> for file in nc_files:
> file_details=get_file_details(file)
> data=get_rain_data(file)
> writer.writerow(('%s' % (file_details[0]),'%s' %
> (file_details[1]),'%f' % float(data[0])))
>
> out_text.close()
> -----
>
> I now get the error:
> -----
> Traceback (most recent call last):
> File
> "F:\Hanlie\UCT\M.Sc\Data\TRMM\lees_netcdf_per_trmm_blok_skryf_vir_pcraster.py",
> line 76, in <module>
> writer.writerow(('%s' % (file_details[0]),'%s' %
> (file_details[1]),'%f' % float(data[0])))
> TypeError: float() argument must be a string or a number
> -----
>
> I tried the other suggestion on the list (posted by Alan Gould),
> namely to replace the %f formatting string with %s in the
> write.writerow statement:
> -----
> writer.writerow( ( file_details[0], file_details[1], str(data[0]) ) )
> -----
>
> This produces a file with lines such as:
> -----
> 20000201 00:00:00 "[0.0, 0.0, 0.0, 0.0]"
> -----
>
> I seem to have a list within a list, I'm not sure why. I could write
> the list elements to variables before I write to the file, but it
> doesn't seem like a very elegant solution.
>
> Can anyone see why I have such a nested data structure? Or is the
> problem something completely different?
>
> Thanks
> Hanlie
>
>
> 2010/10/14, Evert Rol <evert....@gmail.com>:
>>> I have a numpy array ('data') that is the result of reading a netCDF
>>> file, and it typically looks like this:
>>>
>>> array([ 0., 0., 0., 0.], dtype=float32)
>>>
>>>
>>> I want to write this, after a date and time, to a CSV file, so the CSV
>>> file would have the entry:
>>>
>>> 2000-02-01,09:00,0.0,0.0,0.0,0.0
>>>
>>>
>>> The code I'm using to test it, is:
>>>
>>> # file_details[0] is the date and file_details[1] is the time
>>> writer.writerow(('%s' % (file_details[0]),'%s' %
>>> (file_details[1]),'%f' % (data[0])))
>>>
>>>
>>> In my opinion, this should give an output line:
>>>
>>> 2000-02-01,09:00,0.0
>>>
>>>
>>> Instead, I get an error
>>>
>>> TypeError: float argument required, not numpy.ndarray
>>>
>>>
>>>
>>> Can someone please explain to me why data[0] is giving a numpy array
>>> rather than one element? I don't understand it, since I get:
>>>
>>>>>> data[0]
>>> 0.0
>>
>> This means very little, since a string '0.0' will show the same output when
>> printed:
>>>>> print '0.0'
>> 0.0
>>
>> The exception says 'TypeError', so try:
>>
>>>>> type(data[0])
>> <type 'numpy.float32'>
>>
>> Which is indeed what you specified at the start using dtype=float32.
>>
>> The standard string formatting doesn't know what to do with a numpy.float32,
>> so you'll need to convert it to a float:
>>
>>>>> '%f' % float(data[0])
>> '0.000000'
>>
>> (use proper float formatting to get at '0.0', which is what you apparently
>> want.)
>>
>>
>> Evert
>>
>>
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