byteordercodes.py
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''' Byteorder utilities for system - numpy byteorder encoding
Converts a variety of string codes for little endian, big endian,
native byte order and swapped byte order to explicit NumPy endian
codes - one of '<' (little endian) or '>' (big endian)
'''
import sys
sys_is_le = sys.byteorder == 'little'
native_code = sys_is_le and '<' or '>'
swapped_code = sys_is_le and '>' or '<'
aliases = {'little': ('little', '<', 'l', 'le'),
'big': ('big', '>', 'b', 'be'),
'native': ('native', '='),
'swapped': ('swapped', 'S')}
def to_numpy_code(code):
"""
Convert various order codings to NumPy format.
Parameters
----------
code : str
The code to convert. It is converted to lower case before parsing.
Legal values are:
'little', 'big', 'l', 'b', 'le', 'be', '<', '>', 'native', '=',
'swapped', 's'.
Returns
-------
out_code : {'<', '>'}
Here '<' is the numpy dtype code for little endian,
and '>' is the code for big endian.
Examples
--------
>>> import sys
>>> sys_is_le == (sys.byteorder == 'little')
True
>>> to_numpy_code('big')
'>'
>>> to_numpy_code('little')
'<'
>>> nc = to_numpy_code('native')
>>> nc == '<' if sys_is_le else nc == '>'
True
>>> sc = to_numpy_code('swapped')
>>> sc == '>' if sys_is_le else sc == '<'
True
"""
code = code.lower()
if code is None:
return native_code
if code in aliases['little']:
return '<'
elif code in aliases['big']:
return '>'
elif code in aliases['native']:
return native_code
elif code in aliases['swapped']:
return swapped_code
else:
raise ValueError(
'We cannot handle byte order %s' % code)