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pythonunpack

What does the comma mean in Python's unpack?

We can simply use:

crc = struct.unpack('>i', data)

why do people write it like this:

(crc,) = struct.unpack('>i', data)

What does the comma mean?

Solution

  • The first variant returns a single-element tuple:

    In [13]: crc = struct.unpack('>i', '0000')

In [14]: crc
Out[14]: (808464432,)

    To get to the value, you have to write crc[0].

    The second variant unpacks the tuple, enabling you to write crc instead of crc[0]:

    In [15]: (crc,) = struct.unpack('>i', '0000')

In [16]: crc
Out[16]: 808464432