PYthon：该代码如何工作？

Question

def color(self):
    name_hash = hash(self.name)

    red = name_hash & 0xFF          # What is this sort of operation? 
    green = (name_hash << 0xFF) & 0xFF            # What does 0xFF used for?
    blue = (name_hash << 0xFFFF) & 0xFF

    make_light_color = lambda x: x / 3 + 0xAA     # Why plux 0xAA?

    red = make_light_color(red)
    green = make_light_color(green)
    blue = make_light_color(blue)

    return 'rgb(%s,%s,%s)' % (red, green, blue)

Answer 1

This code is trying to convert a hash value to a color; parts of the computation are buggy. It takes the lowest 24 bits of name_hash , splits them into 3 bytes, makes those colors lighter, and then outputs that as a string. Going through the sections:

red = name_hash & 0xFF

Gets the least significant 8 bits of name_hash (the & operation is bitwise AND, and 0xFF selects the lowest 8 bits). The lines for green and blue are buggy; they should be:

green = (name_hash >> 8) & 0xFF
blue = (name_hash >> 16) & 0xFF

to get the middle and high blocks of 8 bits each from name_hash . The make_light_color function does what the name says: it changes a color value from 0 to 255 into one from 170 to 255 (170 is 2/3 of the way from 0 to 255) to make it represent a lighter color. Finally, the last line converts the values of the three separate variables into a string.

Answer 2

Where did you find this code?

• & is the binary AND operation, ANDing with 0xFF would result in all the bits in your character which are 1 for the 2 byte word.

• << is the left shift operation, which would move the bits towards left and append 0's to the right.

• The 0xAA seems to be some operation to perform a color transition, that is modify the bit values to make the color light.