Python分页转Mybatis pagehelper格式分页
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最近工作里遇到一个需求要把之前用Java写的一个http接口替换成用Python写的，出参是带了mybatis pageHelper中PageInfo信息的一个JSON串，而Python这边分页不会涉及到数据库查询，属于直接对list进行分页。。然后就有了下面的对开源Python分页模块的一个改写（模块地址：https://github.com/Pylons/paginate）。至于改动~~emmm~具体来说，就是加了个元类，给原先的Page类动态加了个返回Java格式的JSON字符串的方法，至于为什么这里用了元类，因为本人是做Java的，才开始接触Python，看到这个高级的特性想试试而且又不知道用什么最合适就这样子用了，希望有熟悉Python的朋友提出指导性意见。（代码展开部分为添加的元类和测试代码，另外在原来的Page类上加上了
class Page(list, metaclass=PageMetaclass)用来指定元类。
）
# Copyright (c) 2007-2012 Christoph Haas <[email protected]> # See the file LICENSE for copying permission. """ paginate: helps split up large collections into individual pages ================================================================ What is pagination? --------------------- This module helps split large lists of items into pages. The user is shown one page at a time and can navigate to other pages. Imagine you are offering a company phonebook and let the user search the entries. The entire search result may contains 23 entries but you want to display no more than 10 entries at once. The first page contains entries 1-10, the second 11-20 and the third 21-23. Each "Page" instance represents the items of one of these three pages. See the documentation of the "Page" class for more information. How do I use it? ------------------ A page of items is represented by the *Page* object. A *Page* gets initialized with these arguments: - The collection of items to pick a range from. Usually just a list. - The page number you want to display. Default is 1: the first page. Now we can make up a collection and create a Page instance of it:: # Create a sample collection of 1000 items >> my_collection = range(1000) # Create a Page object for the 3rd page (20 items per page is the default) >> my_page = Page(my_collection, page=3) # The page object can be printed as a string to get its details >> str(my_page) Page: Collection type: <type ‘range‘> Current page: 3 First item: 41 Last item: 60 First page: 1 Last page: 50 Previous page: 2 Next page: 4 Items per page: 20 Number of items: 1000 Number of pages: 50 # Print a list of items on the current page >> my_page.items [40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59] # The *Page* object can be used as an iterator: >> for my_item in my_page: print(my_item) 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 # The .pager() method returns an HTML fragment with links to surrounding pages. >> my_page.pager(url="http://example.org/foo/page=$page") <a href="http://example.org/foo/page=1">1</a> <a href="http://example.org/foo/page=2">2</a> 3 <a href="http://example.org/foo/page=4">4</a> <a href="http://example.org/foo/page=5">5</a> .. <a href="http://example.org/foo/page=50">50</a>‘ # Without the HTML it would just look like: # 1 2 [3] 4 5 .. 50 # The pager can be customized: >> my_page.pager(‘$link_previous ~3~ $link_next (Page $page of $page_count)‘, url="http://example.org/foo/page=$page") <a href="http://example.org/foo/page=2"><</a> <a href="http://example.org/foo/page=1">1</a> <a href="http://example.org/foo/page=2">2</a> 3 <a href="http://example.org/foo/page=4">4</a> <a href="http://example.org/foo/page=5">5</a> <a href="http://example.org/foo/page=6">6</a> .. <a href="http://example.org/foo/page=50">50</a> <a href="http://example.org/foo/page=4">></a> (Page 3 of 50) # Without the HTML it would just look like: # 1 2 [3] 4 5 6 .. 50 > (Page 3 of 50) # The url argument to the pager method can be omitted when an url_maker is # given during instantiation: >> my_page = Page(my_collection, page=3, url_maker=lambda p: "http://example.org/%s" % p) >> page.pager() There are some interesting parameters that customize the Page‘s behavior. See the documentation on ``Page`` and ``Page.pager()``. Notes ------- Page numbers and item numbers start at 1. This concept has been used because users expect that the first page has number 1 and the first item on a page also has number 1. So if you want to use the page‘s items by their index number please note that you have to subtract 1. """ # from common.paginate.page_info import PageMetaclass __author__ = "Christoph Haas" __copyright__ = "Copyright 2007-2016 Christoph Haas and contributors" __credits__ = ["Mike Orr"] __license__ = "MIT" __version__ = "0.5.4" __maintainer__ = "Marcin Lulek, Luke Crooks" __email__ = "[email protected], [email protected]" __status__ = "Beta" import re from string import Template import sys # are we running at least python 3.x ? PY3 = sys.version_info[0] >= 3 if PY3: unicode = str
#元类定义：
class PageMetaclass(type): def __new__(cls, name, bases, attrs): attrs[‘to_java_str‘] = PageMetaclass.to_java_str return type.__new__(cls, name, bases, attrs) def to_java_str(self): page_dict = { "endRow": self.last_item, "firstPage": self.first_page, "hasNextPage": not self.next_page is None, "hasPreviousPage": not self.previous_page is None, "isFirstPage": self.page == self.first_page, "isLastPage": self.page == self.last_page, "lastPage": self.last_page, "list": self.items, "navigatePages": 0, "navigatepageNums": list(range(self.first_page, self.last_page + 1)), "nextPage": self.next_page, "pageNum": self.page, "pageSize": self.items_per_page, "pages": 1 + self.item_count // self.items_per_page, "prePage": self.previous_page, "size": self.last_item - self.first_item + 1, "startRow": self.first_item, "total": self.item_count } s = str(page_dict) s = re.sub(‘‘‘, """, s) s = re.sub(‘True‘, "true", s) s = re.sub(‘False‘, "false", s) s = re.sub(‘None‘, "null", s) return s
# Since the items on a page are mainly a list we subclass the "list" type class Page(list, metaclass=PageMetaclass): """A list/iterator representing the items on one page of a larger collection. An instance of the "Page" class is created from a _collection_ which is any list-like object that allows random access to its elements. The instance works as an iterator running from the first item to the last item on the given page. The Page.pager() method creates a link list allowing the user to go to other pages. A "Page" does not only carry the items on a certain page. It gives you additional information about the page in these "Page" object attributes: item_count Number of items in the collection **WARNING:** Unless you pass in an item_count, a count will be performed on the collection every time a Page instance is created. page Number of the current page items_per_page Maximal number of items displayed on a page first_page Number of the first page - usually 1 :) last_page Number of the last page previous_page Number of the previous page. If this is the first page it returns None. next_page Number of the next page. If this is the last page it returns None. page_count Number of pages items Sequence/iterator of items on the current page first_item Index of first item on the current page - starts with 1 last_item Index of last item on the current page """ def __init__( self, collection, page=1, items_per_page=20, item_count=None, wrapper_class=None, url_maker=None, **kwargs ): """Create a "Page" instance. Parameters: collection Sequence representing the collection of items to page through. page The requested page number - starts with 1. Default: 1. items_per_page The maximal number of items to be displayed per page. Default: 20. item_count (optional) The total number of items in the collection - if known. If this parameter is not given then the paginator will count the number of elements in the collection every time a "Page" is created. Giving this parameter will speed up things. In a busy real-life application you may want to cache the number of items. url_maker (optional) Callback to generate the URL of other pages, given its numbers. Must accept one int parameter and return a URI string. """ if collection is not None: if wrapper_class is None: # Default case. The collection is already a list-type object. self.collection = collection else: # Special case. A custom wrapper class is used to access elements of the collection. self.collection = wrapper_class(collection) else: self.collection = [] self.collection_type = type(collection) if url_maker is not None: self.url_maker = url_maker else: self.url_maker = self._default_url_maker # Assign kwargs to self self.kwargs = kwargs # The self.page is the number of the current page. # The first page has the number 1! try: self.page = int(page) # make it int() if we get it as a string except (ValueError, TypeError): self.page = 1 # normally page should be always at least 1 but the original maintainer # decided that for empty collection and empty page it can be...0? (based on tests) # preserving behavior for BW compat if self.page < 1: self.page = 1 self.items_per_page = items_per_page # We subclassed "list" so we need to call its init() method # and fill the new list with the items to be displayed on the page. # We use list() so that the items on the current page are retrieved # only once. In an SQL context that could otherwise lead to running the # same SQL query every time items would be accessed. # We do this here, prior to calling len() on the collection so that a # wrapper class can execute a query with the knowledge of what the # slice will be (for efficiency) and, in the same query, ask for the # total number of items and only execute one query. try: first = (self.page - 1) * items_per_page last = first + items_per_page self.items = list(self.collection[first:last]) except TypeError: raise TypeError( "Your collection of type {} cannot be handled " "by paginate.".format(type(self.collection)) ) # Unless the user tells us how many items the collections has # we calculate that ourselves. if item_count is not None: self.item_count = item_count else: self.item_count = len(self.collection) # Compute the number of the first and last available page if self.item_count > 0: self.first_page = 1 self.page_count = ((self.item_count - 1) // self.items_per_page) + 1 self.last_page = self.first_page + self.page_count - 1 # Make sure that the requested page number is the range of valid pages if self.page > self.last_page: self.page = self.last_page elif self.page < self.first_page: self.page = self.first_page # Note: the number of items on this page can be less than # items_per_page if the last page is not full self.first_item = (self.page - 1) * items_per_page + 1 self.last_item = min(self.first_item + items_per_page - 1, self.item_count) # Links to previous and next page if self.page > self.first_page: self.previous_page = self.page - 1 else: self.previous_page = None if self.page < self.last_page: self.next_page = self.page + 1 else: self.next_page = None # No items available else: self.first_page = None self.page_count = 0 self.last_page = None self.first_item = None self.last_item = None self.previous_page = None self.next_page = None self.items = [] # This is a subclass of the ‘list‘ type. Initialise the list now. list.__init__(self, self.items) def __str__(self): return ( "Page: " "Collection type: {0.collection_type} " "Current page: {0.page} " "First item: {0.first_item} " "Last item: {0.last_item} " "First page: {0.first_page} " "Last page: {0.last_page} " "Previous page: {0.previous_page} " "Next page: {0.next_page} " "Items per page: {0.items_per_page} " "Total number of items: {0.item_count} " "Number of pages: {0.page_count} " ).format(self) def __repr__(self): return "<paginate.Page: Page {0}/{1}>".format(self.page, self.page_count) def pager( self, format="~2~", url=None, show_if_single_page=False, separator=" ", symbol_first="<<", symbol_last=">>", symbol_previous="<", symbol_next=">", link_attr=None, curpage_attr=None, dotdot_attr=None, link_tag=None, ): """ Return string with links to other pages (e.g. ‘1 .. 5 6 7 [8] 9 10 11 .. 50‘). format: Format string that defines how the pager is rendered. The string can contain the following $-tokens that are substituted by the string.Template module: - $first_page: number of first reachable page - $last_page: number of last reachable page - $page: number of currently selected page - $page_count: number of reachable pages - $items_per_page: maximal number of items per page - $first_item: index of first item on the current page - $last_item: index of last item on the current page - $item_count: total number of items - $link_first: link to first page (unless this is first page) - $link_last: link to last page (unless this is last page) - $link_previous: link to previous page (unless this is first page) - $link_next: link to next page (unless this is last page) To render a range of pages the token ‘~3~‘ can be used. The number sets the radius of pages around the current page. Example for a range with radius 3: ‘1 .. 5 6 7 [8] 9 10 11 .. 50‘ Default: ‘~2~‘ url The URL that page links will point to. Make sure it contains the string $page which will be replaced by the actual page number. Must be given unless a url_maker is specified to __init__, in which case this parameter is ignored. symbol_first String to be displayed as the text for the $link_first link above. Default: ‘<<‘ (<<) symbol_last String to be displayed as the text for the $link_last link above. Default: ‘>>‘ (>>) symbol_previous String to be displayed as the text for the $link_previous link above. Default: ‘<‘ (<) symbol_next String to be displayed as the text for the $link_next link above. Default: ‘>‘ (>) separator: String that is used to separate page links/numbers in the above range of pages. Default: ‘ ‘ show_if_single_page: if True the navigator will be shown even if there is only one page. Default: False link_attr (optional) A dictionary of attributes that get added to A-HREF links pointing to other pages. Can be used to define a CSS style or class to customize the look of links. Example: { ‘style‘:‘border: 1px solid green‘ } Example: { ‘class‘:‘pager_link‘ } curpage_attr (optional) A dictionary of attributes that get added to the current page number in the pager (which is obviously not a link). If this dictionary is not empty then the elements will be wrapped in a SPAN tag with the given attributes. Example: { ‘style‘:‘border: 3px solid blue‘ } Example: { ‘class‘:‘pager_curpage‘ } dotdot_attr (optional) A dictionary of attributes that get added to the ‘..‘ string in the pager (which is obviously not a link). If this dictionary is not empty then the elements will be wrapped in a SPAN tag with the given attributes. Example: { ‘style‘:‘color: #808080‘ } Example: { ‘class‘:‘pager_dotdot‘ } link_tag (optional) A callable that accepts single argument `page` (page link information) and generates string with html that represents the link for specific page. Page objects are supplied from `link_map()` so the keys are the same. """ link_attr = link_attr or {} curpage_attr = curpage_attr or {} dotdot_attr = dotdot_attr or {} self.curpage_attr = curpage_attr self.separator = separator self.link_attr = link_attr self.dotdot_attr = dotdot_attr self.url = url self.link_tag = link_tag or self.default_link_tag # Don‘t show navigator if there is no more than one page if self.page_count == 0 or (self.page_count == 1 and not show_if_single_page): return "" regex_res = re.search(r"~(d+)~", format) if regex_res: radius = regex_res.group(1) else: radius = 2 radius = int(radius) self.radius = radius link_map = self.link_map( format=format, url=url, show_if_single_page=show_if_single_page, separator=separator, symbol_first=symbol_first, symbol_last=symbol_last, symbol_previous=symbol_previous, symbol_next=symbol_next, link_attr=link_attr, curpage_attr=curpage_attr, dotdot_attr=dotdot_attr, ) links_markup = self._range(link_map, radius) # Replace ~...~ in token format by range of pages result = re.sub(r"~(d+)~", links_markup, format) link_first = ( self.page > self.first_page and self.link_tag(link_map["first_page"]) or "" ) link_last = ( self.page < self.last_page and self.link_tag(link_map["last_page"]) or "" ) link_previous = ( self.previous_page and self.link_tag(link_map["previous_page"]) or "" ) link_next = self.next_page and self.link_tag(link_map["next_page"]) or "" # Interpolate ‘$‘ variables result = Template(result).safe_substitute( { "first_page": self.first_page, "last_page": self.last_page, "page": self.page, "page_count": self.page_count, "items_per_page": self.items_per_page, "first_item": self.first_item, "last_item": self.last_item, "item_count": self.item_count, "link_first": link_first, "link_last": link_last, "link_previous": link_previous, "link_next": link_next, } ) return result def link_map( self, format="~2~", url=None, show_if_single_page=False, separator=" ", symbol_first="<<", symbol_last=">>", symbol_previous="<", symbol_next=">", link_attr=None, curpage_attr=None, dotdot_attr=None, ): """ Return map with links to other pages if default pager() function is not suitable solution. format: Format string that defines how the pager would be normally rendered rendered. Uses same arguments as pager() method, but returns a simple dictionary in form of: {‘current_page‘: {‘attrs‘: {}, ‘href‘: ‘http://example.org/foo/page=1‘, ‘value‘: 1}, ‘first_page‘: {‘attrs‘: {}, ‘href‘: ‘http://example.org/foo/page=1‘, ‘type‘: ‘first_page‘, ‘value‘: 1}, ‘last_page‘: {‘attrs‘: {}, ‘href‘: ‘http://example.org/foo/page=8‘, ‘type‘: ‘last_page‘, ‘value‘: 8}, ‘next_page‘: {‘attrs‘: {}, ‘href‘: ‘HREF‘, ‘type‘: ‘next_page‘, ‘value‘: 2}, ‘previous_page‘: None, ‘range_pages‘: [{‘attrs‘: {}, ‘href‘: ‘http://example.org/foo/page=1‘, ‘type‘: ‘current_page‘, ‘value‘: 1}, .... {‘attrs‘: {}, ‘href‘: ‘‘, ‘type‘: ‘span‘, ‘value‘: ‘..‘}]} The string can contain the following $-tokens that are substituted by the string.Template module: - $first_page: number of first reachable page - $last_page: number of last reachable page - $page: number of currently selected page - $page_count: number of reachable pages - $items_per_page: maximal number of items per page - $first_item: index of first item on the current page - $last_item: index of last item on the current page - $item_count: total number of items - $link_first: link to first page (unless this is first page) - $link_last: link to last page (unless this is last page) - $link_previous: link to previous page (unless this is first page) - $link_next: link to next page (unless this is last page) To render a range of pages the token ‘~3~‘ can be used. The number sets the radius of pages around the current page. Example for a range with radius 3: ‘1 .. 5 6 7 [8] 9 10 11 .. 50‘ Default: ‘~2~‘ url The URL that page links will point to. Make sure it contains the string $page which will be replaced by the actual page number. Must be given unless a url_maker is specified to __init__, in which case this parameter is ignored. symbol_first String to be displayed as the text for the $link_first link above. Default: ‘<<‘ (<<) symbol_last String to be displayed as the text for the $link_last link above. Default: ‘>>‘ (>>) symbol_previous String to be displayed as the text for the $link_previous link above. Default: ‘<‘ (<) symbol_next String to be displayed as the text for the $link_next link above. Default: ‘>‘ (>) separator: String that is used to separate page links/numbers in the above range of pages. Default: ‘ ‘ show_if_single_page: if True the navigator will be shown even if there is only one page. Default: False link_attr (optional) A dictionary of attributes that get added to A-HREF links pointing to other pages. Can be used to define a CSS style or class to customize the look of links. Example: { ‘style‘:‘border: 1px solid green‘ } Example: { ‘class‘:‘pager_link‘ } curpage_attr (optional) A dictionary of attributes that get added to the current page number in the pager (which is obviously not a link). If this dictionary is not empty then the elements will be wrapped in a SPAN tag with the given attributes. Example: { ‘style‘:‘border: 3px solid blue‘ } Example: { ‘class‘:‘pager_curpage‘ } dotdot_attr (optional) A dictionary of attributes that get added to the ‘..‘ string in the pager (which is obviously not a link). If this dictionary is not empty then the elements will be wrapped in a SPAN tag with the given attributes. Example: { ‘style‘:‘color: #808080‘ } Example: { ‘class‘:‘pager_dotdot‘ } """ link_attr = link_attr or {} curpage_attr = curpage_attr or {} dotdot_attr = dotdot_attr or {} self.curpage_attr = curpage_attr self.separator = separator self.link_attr = link_attr self.dotdot_attr = dotdot_attr self.url = url regex_res = re.search(r"~(d+)~", format) if regex_res: radius = regex_res.group(1) else: radius = 2 radius = int(radius) self.radius = radius # Compute the first and last page number within the radius # e.g. ‘1 .. 5 6 [7] 8 9 .. 12‘ # -> leftmost_page = 5 # -> rightmost_page = 9 leftmost_page = ( max(self.first_page, (self.page - radius)) if self.first_page else None ) rightmost_page = ( min(self.last_page, (self.page + radius)) if self.last_page else None ) nav_items = { "first_page": None, "last_page": None, "previous_page": None, "next_page": None, "current_page": None, "radius": self.radius, "range_pages": [], } if leftmost_page is None or rightmost_page is None: return nav_items nav_items["first_page"] = { "type": "first_page", "value": unicode(symbol_first), "attrs": self.link_attr, "number": self.first_page, "href": self.url_maker(self.first_page), } # Insert dots if there are pages between the first page # and the currently displayed page range if leftmost_page - self.first_page > 1: # Wrap in a SPAN tag if dotdot_attr is set nav_items["range_pages"].append( { "type": "span", "value": "..", "attrs": self.dotdot_attr, "href": "", "number": None, } ) for thispage in range(leftmost_page, rightmost_page + 1): # Highlight the current page number and do not use a link if thispage == self.page: # Wrap in a SPAN tag if curpage_attr is set nav_items["range_pages"].append( { "type": "current_page", "value": unicode(thispage), "number": thispage, "attrs": self.curpage_attr, "href": self.url_maker(thispage), } ) nav_items["current_page"] = { "value": thispage, "attrs": self.curpage_attr, "type": "current_page", "href": self.url_maker(thispage), } # Otherwise create just a link to that page else: nav_items["range_pages"].append( { "type": "page", "value": unicode(thispage), "number": thispage, "attrs": self.link_attr, "href": self.url_maker(thispage), } ) # Insert dots if there are pages between the displayed # page numbers and the end of the page range if self.last_page - rightmost_page > 1: # Wrap in a SPAN tag if dotdot_attr is set nav_items["range_pages"].append( { "type": "span", "value": "..", "attrs": self.dotdot_attr, "href": "", "number": None, } ) # Create a link to the very last page (unless we are on the last # page or there would be no need to insert ‘..‘ spacers) nav_items["last_page"] = { "type": "last_page", "value": unicode(symbol_last), "attrs": self.link_attr, "href": self.url_maker(self.last_page), "number": self.last_page, } nav_items["previous_page"] = { "type": "previous_page", "value": unicode(symbol_previous), "attrs": self.link_attr, "number": self.previous_page or self.first_page, "href": self.url_maker(self.previous_page or self.first_page), } nav_items["next_page"] = { "type": "next_page", "value": unicode(symbol_next), "attrs": self.link_attr, "number": self.next_page or self.last_page, "href": self.url_maker(self.next_page or self.last_page), } return nav_items def _range(self, link_map, radius): """ Return range of linked pages to substiture placeholder in pattern """ leftmost_page = max(self.first_page, (self.page - radius)) rightmost_page = min(self.last_page, (self.page + radius)) nav_items = [] # Create a link to the first page (unless we are on the first page # or there would be no need to insert ‘..‘ spacers) if self.page != self.first_page and self.first_page < leftmost_page: page = link_map["first_page"].copy() page["value"] = unicode(page["number"]) nav_items.append(self.link_tag(page)) for item in link_map["range_pages"]: nav_items.append(self.link_tag(item)) # Create a link to the very last page (unless we are on the last # page or there would be no need to insert ‘..‘ spacers) if self.page != self.last_page and rightmost_page < self.last_page: page = link_map["last_page"].copy() page["value"] = unicode(page["number"]) nav_items.append(self.link_tag(page)) return self.separator.join(nav_items) def _default_url_maker(self, page_number): if self.url is None: raise Exception( "You need to specify a ‘url‘ parameter containing a ‘$page‘ placeholder." ) if "$page" not in self.url: raise Exception("The ‘url‘ parameter must contain a ‘$page‘ placeholder.") return self.url.replace("$page", unicode(page_number)) @staticmethod def default_link_tag(item): """ Create an A-HREF tag that points to another page. """ text = item["value"] target_url = item["href"] if not item["href"] or item["type"] in ("span", "current_page"): if item["attrs"]: text = make_html_tag("span", **item["attrs"]) + text + "</span>" return text return make_html_tag("a", text=text, href=target_url, **item["attrs"]) def make_html_tag(tag, text=None, **params): """Create an HTML tag string. tag The HTML tag to use (e.g. ‘a‘, ‘span‘ or ‘div‘) text The text to enclose between opening and closing tag. If no text is specified then only the opening tag is returned. Example:: make_html_tag(‘a‘, text="Hello", href="/another/page") -> <a href="/another/page">Hello</a> To use reserved Python keywords like "class" as a parameter prepend it with an underscore. Instead of "class=‘green‘" use "_class=‘green‘". Warning: Quotes and apostrophes are not escaped.""" params_string = "" # Parameters are passed. Turn the dict into a string like "a=1 b=2 c=3" string. for key, value in sorted(params.items()): # Strip off a leading underscore from the attribute‘s key to allow attributes like ‘_class‘ # to be used as a CSS class specification instead of the reserved Python keyword ‘class‘. key = key.lstrip("_") params_string += u‘ {0}="{1}"‘.format(key, value) # Create the tag string tag_string = u"<{0}{1}>".format(tag, params_string) # Add text and closing tag if required. if text: tag_string += u"{0}</{1}>".format(text, tag) return tag_string
# 测试代码
if __name__ == ‘__main__‘: items = [{"questionId": str(var + 1), "seqNo": str(var + 1)} for var in range(100)] page = Page(items, page=0, items_per_page=15) json_str = page.to_java_str() print("json_str: " + json_str)