I have a dictionary. Each key contains a list. I am using the contents of the list to build a portion of a command line.
However, before I can build the command line, I have to make sure that the command isn't too long.
Depending on how you join the list items, you may just be able to use join followed by stdlib textwrap to do this in one step (note I've wrapped this example at width 20 rather than 200 to make the resulting list easier to read):
>>> source = ["some", "text", "fragments", "in", "a", "list"] * 10
>>> import textwrap
>>> textwrap.wrap(" ".join(source),20)
['some text fragments', 'in a list some text', 'fragments in a list', 'some text fragments', 'in a list some text', 'fragments in a list', 'some text fragments', 'in a list some text', 'fragments in a list', 'some text fragments', 'in a list some text', 'fragments in a list', 'some text fragments', 'in a list some text', 'fragments in a list']
This works because the join separator is whitespace, which textwrap ignores. If however, you need a non-whitespace separator, then textwrap can lead to ugly results with a leading or trailing separator:
>>> textwrap.wrap(", ".join(source),20)
['some, fragments, of,', 'text, some,', 'fragments, of, text,', 'some, fragments, of,', 'text, some,', 'fragments, of, text,', 'some, fragments, of,', 'text, some,', 'fragments, of, text,', 'some, fragments, of,', 'text, some,', 'fragments, of, text,', 'some, fragments, of,', 'text, some,', 'fragments, of, text']
If you care about this, you may be able to tweak textwrap.TextWrapper to handle this, or you could use your own function, like:
def iterjoin(iterable, separator = " ", width = 70): """joins an iterable of strings into strings with width <= maxlen Not (yet) rejected for inclusion in itertools ;-)""" accumulator = [] len_accumulator = 0 len_sep = len(separator) for item in iterable: item = item.expandtabs() len_item = len(item) trial_len = len_accumulator + len_sep + len_item if trial_len > width: yield separator.join(accumulator) accumulator = [item] len_accumulator = len_item else: # continue to build the command accumulator.append(item) len_accumulator = trial_len if accumulator: yield separator.join(accumulator)
>>> list(iterjoin(source, ", ", width = 20))
['some, fragments', 'of, text, some', 'fragments, of, text', 'some, fragments, of', 'text, some', 'fragments, of, text', 'some, fragments, of', 'text, some', 'fragments, of, text', 'some, fragments, of', 'text, some', 'fragments, of, text', 'some, fragments, of', 'text, some', 'fragments, of, text']
>>>
Now you can simply iterate over each list in your dictionary:
for k in d:
for command in iterjoin(d[k], your_separator_here, width = 200)HTH
Michael
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