Python: Convert array into integer

Question

I was wondering if there is a way in Python to convert an array or a list into one single number:

A=[0xaa,0xbb,0xcc]

d=0xaabbcc

Thanks for your help!

Answer 1

For Python3+, int has a method for this

>>> A=[0xaa, 0xbb, 0xcc]
>>> hex(int.from_bytes(A, byteorder="big"))
'0xaabbcc'
>>> 0xaabbcc == int.from_bytes(A, byteorder="big")
True

For Python2, it's probably best to write a small function

>>> A = [0xaa, 0xbb, 0xcc]
>>> 
>>> def to_hex(arr):
... res = 0
... for i in arr:
... res <<= 8
... res += i
... return res
... 
>>> 0xaabbcc == to_hex(A)
True

Answer 2

Use hex(), map(), and join().

>>> '0x' + ''.join(map(hex, A)).replace('0x', '')
'0xaabbcc'

Or with lambda:

>>> '0x' + ''.join(map(lambda x: hex(x)[2:], A))
'0xaabbcc'

Thanks to @John La Rooy for pointing out that this fails with 1-digit numbers. The following modification of the lambda version is better:

>>> B = [0x1, 0x4, 0x3]
>>> '0x' + ''.join(map(lambda x: hex(x)[2:].rjust(2, '0'), B))
'0x010403'

But at that point it's better to use John's answer.

• John La Rooy: What if some elements of A are < 0x10?

Answer 3

A = [0xaa, 0xbb, 0xcc]
d = reduce(lambda x, y: x*256 + y, A)
print hex(d)

• Konstantin: I suggest you to use x << y.bit_length() instead of x*256 to make your code more flexible
• dlask: @Alik You are right, but only if the original question wants to deal with bits instead of bytes. Please note that for a = 1 the a.bit_length() gives 1.
• Konstantin: Oh, I didn't think about the question this way. I think OP should clarify what he wants to do.