使用python从二进制文件中读取数字数据

Question

I would like to read a binary data file that contains a header part (text) and then a numeric array. I can use f.read(block_size) to keep streaming in the header part, but what is the best way to read the numeric array?

In MatLab, I could do

fid = fopen(data_file_name, 'rb');
line = fread(fid, block_size, '*char'); 
data = fread(fid, 'long');

In Python, what I have done is

f = open(data_file_name, 'rb')
header = f.read(block_size)

and from here I do not know how to get to the numeric array.

Answer 1

You can use struct.unpack to unpack the numeric data.

eg

with open('file','rb') as fin:
    header = fin.read(header_size)
    data_str = fin.read(num_data_bytes)
    data_tuple = struct.unpack('100f',data_str)  #100 4-byte floats

Depending on the data, you can read it directly to a numpy array using numpy.fromfile . That function accepts an open file object, so you can read the header and then pass the open file object in so numpy can read the data. In this question , I asked about the details of reading binary data from a string into a numpy array. It's a slightly different problem, but much of the answer there applies to this as well (how to specify endianness, etc.)