math - How can we truncate a power series and convert it to a polynomial in sympy? -

i truncate power series in sympy , use result polynomial. i'm doing bit ugly (example degree 4):

truncated_series = 0 i,term in zip(range(5), f.lseries()):     truncated_series += term 

is there better way?

do mean this?

in [1]: f = sin(x)  in [2]: s = series(f, x, 0, 5)  in [3]: s out[3]:       3             x     / 5\ x - -- + o\x /     6           in [4]: s.removeo() out[4]:     3       x      - -- + x   6      

these steps straightforward.

if instead instist on using .lseries(), do:

in [5]: import itertools    in [6]: add(*itertools.islice(f.lseries(), 5)) out[6]:     9       7      5    3       x       x      x    x      ------ - ---- + --- - -- + x 362880   5040   120   6     

explanation: islice picks 5 elements generator, passed arguments add class, managed sympy's additions.