CODEWITHSUNDEEP
python-3.xintegerstruct.pack
Bram
Bram

Reputation: 8273

Writing a large list of short integers with python

I have a large list of values, which I want written to a file, as short integers.

I want to do this efficiently, and in Python3.

One value at a time, is possible using the struct module:

struct.pack( "h", val )

It is possible to prefix the format entry with a count, like so:

struct.pack( "4h", val0,val1,val2,val3 )

But when I try to construct the format dynamically, and write it in one go, I can't feed in a list.

For example:

values = [ x for x in range(100) ]
fmt = "%dh" % ( len(values), )
p = struct.pack( fmt, values )

Will give the error: struct.error: pack expected 100 items for packing (got 1)

How can I efficiently dump a large number of short integers into a file?

Basically, the Python equivalent of the C code:

short values[100];
fwrite( values, sizeof(values), 1, f);

Or am I forced to write these values one at a time if I use Python?

Upvotes: 1

Views: 246

Answers (1)

wim
wim

Reputation: 362707

Just changing one character:

p = struct.pack(fmt, *values)

Upvotes: 2

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