Is it possible to skip over bytes when using Python's struct.unpack?

Question

It is possible to use Python's struct.unpack to extract the useful values from a Bitmap file header, as follows:

magic, file_size, _, _, data_offset = struct.unpack('<2sLHHL', file_header)
assert magic == 'BM'

Is there any way to avoid the need to assign to _ (or another throwaway variable) here? Is it possible to change the format string to make struct.unpack skip over the two unused H fields?

Torben Klein · Accepted Answer · 2019-01-07 12:27:03Z

9

Yes, use the "x" code to skip 1 byte. (see here: https://docs.python.org/2/library/struct.html#format-characters)

I.e., replace "H" with "xx" in the format code.

answered Jan 7, 2019 at 12:27

Torben Klein

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1 Comment

Sam Mason Over a year ago

note that you can use the count prefix to indicate an arbitrary number of bytes, i.e. 4x would discard the 4 bytes that were previously being captured by HH

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