.npy info #numpy

npy_info.py

import struct, ast

def npy_info(fh):
    """Get information about a .npy file, without reading in all the data.
    
    See http://docs.scipy.org/doc/numpy/neps/npy-format.html
    """
    
    # Check magic number
    if fh.read(6) != b'\x93NUMPY':
        raise IOError('Magic number not found, file is not .npy format or is corrupt')
        
    # Get version
    major, minor = struct.unpack('bb', fh.read(2))
    
    # Header length
    if major == 1:
        header_len, = struct.unpack('<h', fh.read(2))
    else:
        header_len, = struct.unpack('<i', fh.read(4))
        
    # Header
    header_str = fh.read(header_len).strip()
    header = ast.literal_eval(header_str)
    
    return dict(
        version=(major, minor),
        header=header,
        data_offset=10 + header_len,
    )