# Flask the front page display
1. Sort principle
There are three ways when querying large amounts of data and display the web:
- All inquiries, screened at end view / client / paging from the database; most of the recording can not cope with the situation, generally do not use;
- Pagination query, a query data in each database query is determined according to the specific request of pages; the number of database queries more;
- Also paged, but a query multiple pages (such as 10), to the client 1, implemented in view; the database requests in terms of reduction than the second method, but the server overhead will be larger;
2. realization
Paging divided into two parts from the functional point:
- Get the current page and add content to html templates;
- Configuration 'previous' after an' other html page content and added to the template;
Generally implemented using paging class, it can be customized;
of course, a frame, FlaskSQLAlchem there Pagination type object. Query object calls paginate a method to obtain Pagination object.
2.1 Paging class
Paging class the following functions:
- Determine the current page record of the serial number, such as 20 records per page, page 5, the page record id should be 81-100;
- Html page generated block code is realized by a method page_html;
The urllib.parse Import urlencode from, quote, unquote
class Pagination (Object):
"" "
custom paging
" ""
DEF the __init __ (Self, current_page, TOTAL_COUNT, the base_url, the params, per_page_count = 10, max_pager_count = 10):
the try:
current_page int = (current_page)
the except Exception AS E:
current_page. 1 =
IF current_page <=. 1:
current_page. 1 =
self.current_page current_page =
total number of data #
self.total_count = TOTAL_COUNT
# 10 per data
self.per_page_count = per_page_count
# the maximum page number of the page should be displayed
max_page_num, divmod = div (TOTAL_COUNT, per_page_count)
# self.params [Page] =. 8
div IF:
max_page_num + =. 1
self.max_page_num = max_page_num
default on page # 11 display the page number (in the middle of this page)
self.max_pager_count = max_pager_count
self.half_max_pager_count = int ((max_pager_count -. 1) / 2)
# the URL prefix
self. = the base_url the base_url
# `` request.GET``
Import Copy
the params = copy.deepcopy (the params)
# params._mutable = True
get_dict params.to_dict = ()
# page containing the current list of all the search / search condition
# {source: [2,] , Status: [2], Gender: [2], Consultant: [. 1], Page: [. 1]}
# Source & Status = 2 = 2 = 2 & Gender & Consultant = =. 8. 1 & Page
# self.params.urlencode()
# href="/hosts/?source=2&status=2&gender=2&consultant=1&page=8"
# href="%s?%s" %(self.base_url,self.params.urlencode())
self.params = get_dict
@property
def start(self):
return (self.current_page - 1) * self.per_page_count
@property
def end(self):
return self.current_page * self.per_page_count
def page_html(self):
# 如果总页数 <= 11
if self.max_page_num <= self.max_pager_count:
pager_start = 1
pager_end = self.max_page_num
# 如果总页数 > 11
else:
# If the current page <= 5
if self.current_page <= self.half_max_pager_count:
pager_start = 1
pager_end = self.max_pager_count
else:
# 当前页 + 5 > 总页码
if (self.current_page + self.half_max_pager_count) > self.max_page_num:
pager_end = self.max_page_num
pager_start = self.max_page_num - self.max_pager_count + 1 #倒这数11个
else:
pager_start = self.current_page - self.half_max_pager_count
pager_end = self.current_page + self.half_max_pager_count
page_html_list = []
# {source:[2,], status:[2], gender:[2],consultant:[1],page:[1]}
# 首页
self.params['page'] = 1
first_page = '首页' % (self.base_url,urlencode(self.params),)
page_html_list.append(first_page)
# 上一页
self.params["page"] = self.current_page - 1
if self.params["page"] <= 1:
pervious_page = '上一页' % (self.base_url, urlencode(self.params))
else:
pervious_page = '上一页' % ( self.base_url, urlencode(self.params))
page_html_list.append(pervious_page)
# 中间页码
for i in range(pager_start, pager_end + 1):
self.params['page'] = i
if i == self.current_page:
temp = '%s' % (self.base_url,urlencode(self.params), i,)
else:
temp = '%s' % (self.base_url,urlencode(self.params), i,)
page_html_list.append(temp)
# 下一页
self.params["page"] = self.current_page + 1
if self.params["page"] > self.max_page_num:
self.params["page"] = self.current_page
next_page = '下一页' % (self.base_url, urlencode(self.params))
else:
next_page = '下一页' % (self.base_url, urlencode(self.params))
page_html_list.append(next_page)
# 尾页
self.params['page'] = self.max_page_num
last_page = '尾页' % (self.base_url, urlencode(self.params),)
page_html_list.append(last_page)
return ''.join(page_html_list)
2.2 Routing
@app.route('/list_t', methods=['GET'])
def list_t():
ori_data = ['第一列', '第二列', '空列']
li = []
for x in range(1000):
li.append(ori_data + [x])
pager_obj = Pagination(request.args.get("page", 1), len(li), request.path, request.args, per_page_count=10)
index_list = li[pager_obj.start:pager_obj.end]
pagination_html = pager_obj.page_html()
return render_template("list_paper.html", index_list=index_list, html=pagination_html)
2.3 html Code
slightly
2.4 demonstration effect
Demonstration effect:
