Find all ways of writing 100 as "1<op>2<op>3...9"

gistfile1.txt

#!/usr/bin/env python

PLUS = '+'
MINUS = '-'
CONCAT = ''
ops = [PLUS, MINUS, CONCAT]

def op_sequences(n):
    if n == 0:
        yield []
        return
    for seq in op_sequences(n-1):
        for op in ops:
            yield [op] + seq

def interleave(xs, ys):
    xi = xs.__iter__()
    yi = ys.__iter__()
    try:
        while True:
            yield xi.__next__()
            yield yi.__next__()
    except StopIteration:
        return

for seq in op_sequences(8):
    calc = ''.join(interleave(map(str, range(1, 10)), seq))
    if eval(calc) == 100:
        print(calc)