在python中将两个数字连接到一个数字的最有效方法是什么？

Question

what is the most efficient way of concat two numbers to one number in python?

numbers are always in between 0 to 255, i have tested few ways by Concat as string and cast back to int but they are very costly in time vice for my code.

example

    a = 152 
    c = 255
    d = concat(a,c)

answer:

    d = 152255

Answer 1

If the numbers are bounded, just multiply and add:

>>> a = 152
>>> c = 255
>>> d = a*1000+c
>>> d
152255
>>>

Answer 2

This is pretty fast:

def concat(a, b):
    return 10**int(log(b, 10)+1)*a+b

It uses the logarithm to find how many times the first number must be multiplied by 10 for the sum to work as a concatenation

In [1]: from math import log

In [2]: a = 152

In [3]: b = 255


In [4]: def concat(a, b):
   ...:     return 10**int(log(b, 10)+1)*a+b
   ...:

In [5]: concat(a, b)
Out[5]: 152255

In [6]: %timeit concat(a, b)
1000000 loops, best of 3: 1.18 us per loop

Answer 3

Yeah, there you go:

a = 152
b = 255

def concat(a, b):
    n = next(x for x in range(10) if 10**x>a)  # concatenates numbers up to 10**10
    return a * 10**n + b

print(concat(a, b))  # -> 152255