Python 字节到浮点数的转换

Question

from struct import *
longValue = 1447460000
print struct.pack('!q',longValue)

The longValue is actually signifies time in epoch as the main idea is to convert the epoch time which is a long, into bytes. So I came across struct module and this seems quite helpful too.

The output that I get is:-

'\x00\x00\x00\x00VF|\xa0'

Now, I want to make sure that this result is correct, so I want to convert these bytes back to the long.

This is what I am trying:-

struct.unpack("<L", "\x00\x00\x00\x00VF|\xa0")

But this gives me error:-

struct.error: unpack requires a string argument of length 4

Any help?Thanks

Answer 1

Use the same struct format, !q , to unpack as you did to pack:

In [6]: import struct

In [7]: longValue = 1447460000

In [8]: struct.pack('!q',longValue)
Out[8]: '\x00\x00\x00\x00VF|\xa0'

In [9]: struct.unpack('!q', struct.pack('!q',longValue))
Out[9]: (1447460000,)

q is for 8-byte long ints , while L is for 4-byte unsigned longs. That is why you got the error

struct.error: unpack requires a string argument of length 4