递增存储为布尔值列表的数字

Question

In this example I'm iterating over all possible variations of a mask, which I store as a list of booleans

Nmax = 32
for num in range (2**Nmax):
    bool_list = [bool(num & (1<<n)) for n in range(Nmax)]
    # other stuff

However, the operation to generate bool_list is a bit of a bottleneck in the code - the rest is rather fast matrix multiplication. Is there a faster way to increment the number stored in bool_list than I'm doing?

Answer 1

You're just taking all combinations of (False, True) Nmax times. Hence,

from itertools
print(list(itertools.product(*[(False, True)]*Nmax)))

will display all the masks.

If you want to use it while iterating,

Nmax = 32
masks = itertools.product(*[(False, True)]*Nmax)
for mask in masks:
    # Do stuff

Note that mask will be a tuple rather than a list.

Answer 2

For one, I think you can precompute the shifts:

Nmax = 32
shifts = [(1 << n) for n in range(Nmax)]
for num in range(2**Nmax):
    bool_list = [bool(num & shift) for shift in shifts]