The most efficient way to compute powers of two!

gistfile1.py

>>> x=""
>>> for i in range(25):
...     print i, len(x)
...     x = repr(x)
...
0 0
1 2
2 4
3 8
4 16
5 32
6 64
7 128
8 256
9 512
10 1024
11 2048
12 4096
13 8192
14 16384
15 32768
16 65536
17 131072
18 262144
19 524288
20 1048576
21 2097152
22 4194304
23 8388608
24 16777216