CODEWITHSUNDEEP
pythonpython-3.xnetwork-programmingstructhex
user10870615
user10870615

Reputation:

Packing and unpacking float values in python

Why does python return "odd values" when I try packing a float object? For example:

>>> import struct,time

>>> struct.pack('d', time.time())
b'\xe0LC|\xf6l\xd7A'

>>> struct.unpack('d', b'\xe0LC|\xf6l\xd7A')
(1572067825.051567,)

Why does it unpack the value as a tuple instead of a float? And then, why does it use values such as LC and | and l -- I thought it would pack the items in hex?

Upvotes: 1

Views: 865

Answers (1)

Stanislas Morbieu
Stanislas Morbieu

Reputation: 1827

The documentation of unpack states explicitly that the result is a tuple:

Unpack from the buffer buffer (presumably packed by pack(format, ...)) according to the format string format. The result is a tuple even if it contains exactly one item. The buffer’s size in bytes must match the size required by the format, as reflected by calcsize().

You can see the representations of all possible bytes with:

for i in range(256):
    print("{} : {}".format(i, bytes([i])))

For instance, 124 is represented by b'|'. In your case, b'\xe0LC|\xf6l\xd7A' is the representation of bytes([224, 76, 67, 124, 246, 108, 215, 65]).

Upvotes: 1

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