I have a list unicode strings representing binary numbers e.g. "010110".
I wish to perform bitwise operations, so how do I convert that to a structure where I can perform bitwise operations on these (preferably an unsigned int)?
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3 Answers
Use int() with the "base" option.
int("010110", 2)
Comments
You can convert the strings to int and then use the regular shift operators on them:
>>> x = int("010110", 2)
>>> x >> 3
2
>>> x << 3
176
1 Comment
cnicutar
@Jon Thanks, the habit of adding a
; is hard to kick.using int() is the most obvious and useful way. but you didn't say if you need these as integers or not.
just in case not, then:
x = '1010100100'
intx = int(x,2)
x
0x2a4
intx >> 5
0x15
bin(intx>>5)
'0b10101'
x[:-5]
'10101'
intx << 3
0x1520
bin(intx<<3)
'0b1010100100000'
x + '0'*3
'1010100100000'
the actual shifts are slower, but the end result isn't necessarily, and not as much slower as you'd think. This is because even though the actual shift is probably a single cycle on most modern architectures, whereas a slice obviously is many more instructions, there is a lot of overhead just looking up arguments etc. that make it not so much difference.
# Shifts are about 40% faster with integers vs. using equivalent string methods
In [331]: %timeit intx>>5
10000000 loops, best of 3: 48.3 ns per loop
In [332]: timeit x[:-5]
10000000 loops, best of 3: 69.9 ns per loop
In [333]: %timeit x+'0'*3
10000000 loops, best of 3: 70.5 ns per loop
In [334]: %timeit intx << 3
10000000 loops, best of 3: 51.7 ns per loop
# But the conversion back to string adds considerable time,
# dependent on the length of the string
In [335]: %timeit bin(intx>>5)
10000000 loops, best of 3: 157 ns per loop
In [338]: %timeit bin(intx<<3)
1000000 loops, best of 3: 242 ns per loop
# The whole process, including string -> int -> shift -> string,
# is about 8x slower than just using the string directly.
In [339]: %timeit int(x,2)>>5
1000000 loops, best of 3: 455 ns per loop
In [341]: %timeit int(x,2)<<3
1000000 loops, best of 3: 378 ns per loop
int(x,2) is probably still your best bet, but just some other ideas for optimization if you have use of it.
