EP 16 Consider Generator Instead of Returning Lists ref: http://qiita.com/giwa/items/e20a575a0b3e6028d532

file0.txt

def index_words(text):
    result = []
    if text:
        result.append(0)
    for index, letter in enumerate(text):
        if letter == ' ':
            result.append(index + 1)
    return result

file1.txt

address = 'Four score and seven years ago...'
result = index_words(address)
print(result[:3])

[0, 5, 11]

file2.txt

def index_words_iter(text):
    if text:
        yield 0
    for index, letter in enumerate(text):
        if letter == ' ':
            yield index + 1


def index_file(handle):
    offset = 0
    for line in handle:
        if line:
            yield offset
        for letter in line:
            offset += 1
            if letter == '':
                yield offset

file3.txt

from itertools import islice

with open('/tmpaddress.txt') as f:
    it = index_file(f)
    result = islice(it, 0, 3)
    print(list(result))