结合for循环和while循环

Question

i'm trying to write a python script that will find X what i mean is

x & 0xe = 0x6

i want to find all of the combinations that can give me the hex result of x & 0xe = 0x6

so the first thing iv'e done is creating a script that test if x & 0xe = 0x6 so i can find some X combinations

GetStr=(raw_input('1st Hex:'))
GetStr2=hex(0xe)

StrToHex=int(GetStr,16)
StrToHex2=int(GetStr2,16)
cal = (hex(StrToHex & StrToHex2))

while cal != hex(0x6):
    print "no"
    GetStr = (raw_input('1st Hex:'))
    GetStr2 = hex(0xe)

    StrToHex = int(GetStr, 16)
    StrToHex2 = int(GetStr2, 16)
    cal = (hex(StrToHex & StrToHex2))
else:
    print GetStr

The second script is a for loop that will create all combinations that will be tested in the while loop

GetStr=(raw_input('1st Hex:'))
StrToHex = int(GetStr, 16)

GetStr2=hex(0x100)
StrToHex2=int(GetStr2,16)

for i in range(StrToHex,StrToHex2,1):
    print hex(i)

The thing is i find it hard to make it work the way i want it, all it needs to do is to find all combinations that could sum to 0x6 and print it.

Thanks!

Answer 1

First, note that it is impossible to find all the values of x such that x & 0xe == 0x6 , because there are infinitely many of them. bin(0x6) is '0b110' and bin(0xe) is '0b1110' , so every number that has all the bits that are in both numbers and any other bits that are not also in 0xe will be a solution.

About your code: Not entirely clear what you are asking. As I understand the question, you want to transform the manual method from the first snippet to a loop automatically testing all the numbers in a certain range. For this, I suggest making a function for the check that you can reuse in both loops, and also defining some variables for the other two values. Also, currently you are constantly converting from int to hex -string and back to int . Just work with int all the time and just convert to hex for printing.

You can try something like this:

# function used in both loops
def check(first, second, target):
    return first & second == target

# manual loop with user input
second, target = 0xe, 0x6
print("find solution for x & 0x%x = 0x%x" % (second, target))
while True:
    first = int(raw_input('1st hex: '), 16)
    if check(first, second, target):
        print("yes")
        break
    else:
        print("no")

Or even shorter (but probably not as readable):

while not check(int(raw_input('1st hex: '), 16), second, target):
    print("no")
print("yes")

Then, just call that function in your for loop.

# automated loop testing values in range
upper = 0x100
for n in range(upper):
    if check(n, second, target):
        print(hex(n))