task_2.py

from inline import Here


def expand_hostname_range(line=None):
    """
    A helper function that expands a given line that contains a pattern
    specified in top docstring, and returns a list that consists of the
    expanded version.

    The '[' and ']' characters are used to maintain the pseudo-code
    appearance. They are replaced in this function with '|' to ease
    string splitting.

    References: https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html#hosts-and-groups
    """
    all_hosts = []
    if line:
        # A hostname such as db[1:6]-node is considered to consists
        # three parts:
        # head: 'db'
        # nrange: [1:6]; range() is a built-in. Can't use the name
        # tail: '-node'

        # Add support for multiple ranges in a host so:
        # db[01:10:3]node-[01:10]
        # - to do this we split off at the first [...] set, getting the list
        #   of hosts and then repeat until none left.
        # - also add an optional third parameter which contains the step. (Default: 1)
        #   so range can be [01:10:2] -> 01 03 05 07 09

        (head, nrange, tail) = line.replace("[", "|", 1).replace("]", "|", 1).split("|")
        # inline test here
        bounds = nrange.split(":")
        if len(bounds) != 2 and len(bounds) != 3:
            raise AnsibleError("host range must be begin:end or begin:end:step")
        beg = bounds[0]
        end = bounds[1]
        if len(bounds) == 2:
            step = 1
        else:
            step = bounds[2]
        if not beg:
            beg = "0"
        if not end:
            raise AnsibleError("host range must specify end value")
        if beg[0] == "0" and len(beg) > 1:
            rlen = len(beg)  # range length formatting hint
            if rlen != len(end):
                raise AnsibleError(
                    "host range must specify equal-length begin and end formats"
                )

            def fill(x):
                return str(x).zfill(rlen)  # range sequence

        else:
            fill = str

        try:
            i_beg = string.ascii_letters.index(beg)
            i_end = string.ascii_letters.index(end)
            if i_beg > i_end:
                raise AnsibleError("host range must have begin <= end")
            seq = list(string.ascii_letters[i_beg : i_end + 1 : int(step)])
        except ValueError:  # not an alpha range
            seq = range(int(beg), int(end) + 1, int(step))

        for rseq in seq:
            hname = "".join((head, fill(rseq), tail))

            if detect_range(hname):
                all_hosts.extend(expand_hostname_range(hname))
            else:
                all_hosts.append(hname)

        return all_hosts