Context Managers

For the next set of examples we're going to need a data file containing some numbers. Using the code in recaman.py below, we'll write a sequence of numbers called Recaman's sequence to a text file, with one number per line:

import sys
from itertools import count, islice

def sequence():
    """Generate Recaman's sequence."""
    seen = set()
    a = 0
    for n in count(1):
        yield a
        seen.add(a)
        c = a - n
        if c < 0 or c in seen:
            c = a + n
        a = c

def write_sequence(filename, num):
    """Write Recaman's sequence to a text file."""
    f = open(filename, mode='wt', encoding='utf-8')
    f.writelines("{0}\n".format(r)
                 for r in islice(sequence(), num + 1))
    f.close()

if __name__ == '__main__...