Python: an elegant way to extract floats from list?

Question

Is there a more elegant way to do this?

I have a "double" list of the form:

rlist = [([-0.5753647], [1.3716470]), ([-0.57536478], [0.75418190]), ([-1.37632438], [0.57068748])]

from which I want to extract individual floating point numbers, formatted.

At the moment I'm using:

first_number = round(float(str(rlist[0][0]).strip('[]')),4)

for example, to get the first number. This is rather ugly. Is there a more succinct way to do it (in Python)?

DN

Answer 1

You can try something like this:

from itertools import chain
[round(x, 4) for x in chain(*chain(*rlist))]

itertools.chain can be used to flatten nested iterables. After that you can use list comprehension and round to obtain list of numbers with required precision.

Answer 2

If you are opting for itertools.chain() , if level of nesting is more please see the comments below this answer by @zero323

And round() has also some restrictions too,

f = -0.5753647

print f

-0.57536469999999995

print round(f, 4)

-0.57540000000000002

So,

rlist = [([-0.5753647], [1.3716470]),
     ([-0.57536478], [0.75418190]),
     ([-1.37632438], [0.57068748])]

def flatten(container):

    for i in container:
        if isinstance(i, list) or isinstance(i, tuple):
            for j in flatten(i):
                yield j
        else:
            yield i

print ["{0:.4f}".format(ele) for ele in list(flatten(rlist))]