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import rrdtool

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"""

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    Friendly wrapper around the rrdtool python interface

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"""

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def normalize_option_key (key) :

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    """

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        Normalize the given option key.

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        A -- is prepended, and _'s are converted to -

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    """

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    return '--' + str(key).replace('_', '-')

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def normalize_option_multi (key, values) :

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    """

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        Normalize a list of option values, returning a series of --opt, val1, --opt, val2, ...

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    """

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    for value in values :

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        yield key

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        yield str(value)

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def normalize_option (key, value) :

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    """

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        Normalize the given option to a series of cmd-args.

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        If value is None or False, no cmd-args are emitted. If value is True, only --opt is emitted. If value is a list,

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        --opt and value are emitted for each item.

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        Otherwise, both --opt and str(value) are emitted.

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    """

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    key = normalize_option_key(key)

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    if value is None or value is False :

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        # omit

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        return ()

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    elif value is True :

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        # flag

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        return (key, )

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    elif isinstance(value, list) :

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        # list of option values

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        return normalize_option_multi(key, value)

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    else :

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        # option value

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        return (key, str(value))

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def run_cmd (func, pre_args, opts, post_args) :

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    """

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        Run the given rrdtool.* function, formatting the given positional arguments and options.

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    """

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    # series of (cmd-arg, cmd-arg, ...) tuples

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    opt_items = (normalize_option(key, value) for key, value in opts.iteritems())

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    # decomposed series of cmd-args

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    opt_args = [item for items in opt_items for item in items]

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    # positional arguments

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    pre_args = [str(arg) for arg in pre_args]

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    post_args = [str(arg) for arg in post_args]

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    # full arguments

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    args = pre_args + opt_args + post_args

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    return func(*args)

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def graph (out_path, *args, **opts) :

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    return run_cmd(rrdtool.graph, (out_path, ), opts, args)

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