Retrieve the current page number from *GET* or *POST* data.

    If the page does not exists in *request*, or is not a number,
    then *default* number is returned.

def get_page_number_from_request(
        request, querystring_key=PAGE_LABEL, default=1):
    """Retrieve the current page number from *GET* or *POST* data.

    If the page does not exists in *request*, or is not a number,
    then *default* number is returned.
    """
    try:
        if request.method == 'POST':
            page_number = request.POST[querystring_key]
        else:
            page_number = request.GET[querystring_key]

        return int(page_number)
    except (KeyError, TypeError, ValueError):
        return default