Read arbitrarily large input, print number closest to zero

nearest-zero.py

from itertools import islice, tee

# Assume an input such:
#
#     3
#     1 -3 4
#     2
#     8 9
#     0
#  
#     4
#     1 3 8 2
#
# Where the first line indicates the number  of integers to be found
# on the next line: find the number on the next line that is nearest 
# to zero (0)

with open("/dev/stdin") as file_:
    
    # Split the `file_` into two iterators...
    cnt_iter, num_iter = tee(file_)
    
    # ... slice each to return every other row but start `num_iter`
    # from index 1 ...
    cnt_iter = islice(cnt_iter, 0, None, 2)
    num_iter = islice(num_iter, 1, None, 2)
    
    # ... iterate both iterators together ...
    for nums, line in zip(cnt_iter, num_iter):
        if int(nums) > 0:
            
            # ... map each into an `int` and get the minimum as is
            # reported by `abs()` -- this "ignores" negative value
            # but still lets us retain their sign.
            ints = map(int, line.split())
            low_ = min(ints, key=abs)
            print(low_)