Generators

Links

Copy of presentation (and source code) by David M. Beazley

Generator Expressions

Generator expressions are shorthand for generators. Just like list comprehensions, but with () instead of []:

In [1]: items = (str(x) for x in range(6))
In [2]: items
Out[2]: <generator object <genexpr> at 0x8d1cb1c>
In [3]: for i in items: print i
0
1
2
3
4
5

Sample

Here is a sample generator:

def get_next_char(valid_chars):
    i = 0
    switch = False
    while True:
        yield valid_chars[i], switch
        if switch:
            switch = False
        i = i + 3
        if i > len(valid_chars) -1:
            i = i - len(valid_chars)
            switch = True

…and here are two different ways of using it:

count = 0
valid_chars = 'XJ62RY9K51FWNC37PE8M4THV0DGLQ'
for char_1, switch_1 in get_next_char(valid_chars):
    count = count + 1
    if switch_1:
        print '|',
    print char_1,
    if count > 50:
        break

x = get_next_char('XJ62RY9K51FWNC37PE8M4THV0DGLQ')
print x.next()
print x.next()