python - 预先获取标题行数

Question

我有一个由标题行和二进制部分组成的二进制文件。 ftp://n5eil01u.ecs.nsidc.org/SAN/GLAS/GLA06.034/2003.02.21/GLA06_634_1102_001_0079_3_01_0001.DAT

我必须知道标题行占用的行数。我怎么能事先知道它，以便我可以将值放在下面以转义 header 部分。

import numpy as np    
fname = 'GLA06_634_1102_001_0079_3_01_0001.DAT' 

with open(fname,'rb') as fi:
    fi.seek (176,0) ##HERE I HAVE TO PUT

Answer 1

来自提供的read file routine :

n_headers = long( read_header( i_file, 'NUMHEAD', error=error) )
recl= long( read_header( i_file, 'RECL', error=error) )
offset=long(recl*n_headers)
print,'offset=',offset
print,'recl   n_headers = ',recl,n_headers
str_vers = 'pv'+strtrim(string(ver1),2)+'_'+ $
             strtrim(string(ver2),2)
print, 'version=',str_vers

header 大小似乎是 recl*n_headers，其中这两个值是前两个 header 。所以:

fname = 'GLA06_634_1102_001_0079_3_01_0001.DAT'

with open(fname,'rb') as fi:
    recl = None
    numhead = None

    # Loop in case the required headers are not the first two one
    # and/or in wrong order
    for line in fi:
        if line.startswith('Recl='):
            recl = int(line[5:-2])
        if line.startswith('Numhead='):
            numhead = int(line[8:-2])

        if recl is not None and numhead is not None:
            break

    offset = recl*numhead

    print "Binary data starts at ", offset
    fi.seek(offset)