URI multi template

uri_multi_expand.py

#!/usr/bin/env python3

import itertools
from uritemplate import URITemplate


def dict_product(a_dict):
    """Iterate over the product of all values of the given dict.

    >>> for d in dict_product({'foo': [1, 2], 'bar': [1, 2]}):
    ...    print(repr(d))
    {'foo': 1, 'bar': 1}
    {'foo': 1, 'bar': 2}
    {'foo': 2, 'bar': 1}
    {'foo': 2, 'bar': 2}
    """
    kvps = [[(key, value) for value in values]
            for key, values in a_dict.items()]
    for single_dict in itertools.product(*kvps):
        yield dict(single_dict)


def combinations_of_any_length(iterable):
    for tuple_length in range(1, 1 + len(iterable)):
        for subsequence in itertools.combinations(iterable, tuple_length):
            yield subsequence


def multi_expand(uri, **kwargs):
    """Expand uri for each possibilities given in each arguments, like:
    >>> for uri in multi_expand(
    ...     "https://api.example.com/search/?q={query}{&page}",
    ...     page=['1', '2', '3'],
    ...     query=['foo', 'bar', 'baz']):
    ...    print(uri)
    https://api.example.com/search/?q=&page=1
    https://api.example.com/search/?q=&page=2
    https://api.example.com/search/?q=&page=3
    https://api.example.com/search/?q=foo
    https://api.example.com/search/?q=bar
    https://api.example.com/search/?q=baz
    https://api.example.com/search/?q=foo&page=1
    https://api.example.com/search/?q=bar&page=1
    https://api.example.com/search/?q=baz&page=1
    https://api.example.com/search/?q=foo&page=2
    https://api.example.com/search/?q=bar&page=2
    https://api.example.com/search/?q=baz&page=2
    https://api.example.com/search/?q=foo&page=3
    https://api.example.com/search/?q=bar&page=3
    https://api.example.com/search/?q=baz&page=3
    """
    tpl = URITemplate(uri)
    missing_variables = set(tpl.variable_names) - set(kwargs.keys())
    if missing_variables:
        raise ValueError("Missing variables: {!r}".format(missing_variables))
    for variable_names in combinations_of_any_length(tpl.variable_names):
        selected_values = {key: value for key, value in kwargs.items() if
                           key in variable_names}
        for set_of_values in dict_product(selected_values):
            yield tpl.expand(set_of_values)