How to convert 4 bytes to an integer ?

[GiggsB]

Hi, I am using SPI on Raspberry Pi (master) and collecting 4 bytes at a time. I need to convert this back to integer. How can I do it?
When I do it using struct...it gives some random garbage values:

        b=spi.readbytes(4)
        value=struct.unpack("<I", bytearray(b))[0]
        print (value)

Thanks.