Home Backend Development Python Tutorial Detailed explanation of python recursive query menu and conversion into json example code

Detailed explanation of python recursive query menu and conversion into json example code

Mar 28, 2017 am 09:16 AM

This article mainly introduces the python recursive query menu and converts it into a json instance. It has certain reference value. Interested friends can refer to it.

I recently needed to write a menu in python, and it took me two or three days to get it done. Now I record it here, and friends who need it can learn from it.

Note: The article quotes the complete non-executable code and only excerpts the key parts of the code

Environment

  • Database: mysql

  • python:3.6

Table structure


CREATE TABLE `tb_menu` (
 `id` varchar(32) NOT NULL COMMENT '唯一标识',
 `menu_name` varchar(40) DEFAULT NULL COMMENT '菜单名称',
 `menu_url` varchar(100) DEFAULT NULL COMMENT '菜单链接',
 `type` varchar(1) DEFAULT NULL COMMENT '类型',
 `parent` varchar(32) DEFAULT NULL COMMENT '父级目录id',
 `del_flag` varchar(1) NOT NULL DEFAULT '0' COMMENT '删除标志 0:不删除 1:已删除',
 `create_time` datetime DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
 `update_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
 PRIMARY KEY (`id`) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='菜单表';
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Python code

In the Menu object, there is a reference to the submenu list "subMenus", the type is list

Core code


def set_subMenus(id, menus):
  """
  根据传递过来的父菜单id,递归设置各层次父菜单的子菜单列表

  :param id: 父级id
  :param menus: 子菜单列表
  :return: 如果这个菜单没有子菜单,返回None;如果有子菜单,返回子菜单列表
  """
  # 记录子菜单列表
  subMenus = []
  # 遍历子菜单
  for m in menus:
    if m.parent == id:
      subMenus.append(m)

  # 把子菜单的子菜单再循环一遍
  for sub in subMenus:
    menus2 = queryByParent(sub.id)
    # 还有子菜单
    if len(menus):
      sub.subMenus = set_subMenus(sub.id, menus2)

  # 子菜单列表不为空
  if len(subMenus):
    return subMenus
  else: # 没有子菜单了
    return None
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Test method


  def test_set_subMenus(self):
    # 一级菜单
    rootMenus = queryByParent('')
    for menu in rootMenus:
      subMenus = queryByParent(menu.id)
      menu.subMenus = set_subMenus(menu.id, subMenus)
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Note: The basic process is: first query the first-level menu, Then pass the id of the menu at this level and the submenu list of this level menu to the set_subMenus method to recursively set the lower-level menus of the submenu list;

supports passing the menu ID and querying the menu below. All submenus. If you pass a null character, the query starts from the root directory

In the "rootMenus" object, you can see the complete menu tree structure

Convert to Json

The ORM framework I use is: sqlalchemy. The Menu object queried directly from the database will report an error when it is converted to Json. A DTO class needs to be redefined to convert the Menu object into a Dto object.

MenuDto


class MenuDto():
  def __init__(self, id, menu_name, menu_url, type, parent, subMenus):
    super().__init__()
    self.id = id
    self.menu_name = menu_name
    self.menu_url = menu_url
    self.type = type
    self.parent = parent
    self.subMenus = subMenus

  def __str__(self):
    return '%s(id=%s,menu_name=%s,menu_url=%s,type=%s,parent=%s)' % (
      self.__class__.__name__, self.id, self.menu_name, self.menu_url, self.type, self.parent)

  __repr = __str__
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So, the method of recursively setting submenus was redefined


def set_subMenuDtos(id, menuDtos):
  """
  根据传递过来的父菜单id,递归设置各层次父菜单的子菜单列表

  :param id: 父级id
  :param menuDtos: 子菜单列表
  :return: 如果这个菜单没有子菜单,返回None;如果有子菜单,返回子菜单列表
  """
  # 记录子菜单列表
  subMenuDtos = []
  # 遍历子菜单
  for m in menuDtos:
    m.name = to_pinyin(m.menu_name)
    if m.parent == id:
      subMenuDtos.append(m)

  # 把子菜单的子菜单再循环一遍
  for sub in subMenuDtos:
    menus2 = queryByParent(sub.id)
    menusDto2 = model_list_2_dto_list(menus2,
                     "MenuDto(id='', menu_name='', menu_url='', type='', parent='', subMenus='')")
    # 还有子菜单
    if len(menuDtos):
      if len(menusDto2):
        sub.subMenus = set_subMenuDtos(sub.id, menusDto2)
      else: # 没有子菜单,删除该节点
        sub.__delattr__('subMenus')

  # 子菜单列表不为空
  if len(subMenuDtos):
    return subMenuDtos
  else: # 没有子菜单了
    return None
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Note:

  1. When a menu has no submenus, delete the "subMenus" attribute, otherwise a null value will appear when converting to Json

  2. model_list_2_dto_list method can convert Menu list into MenuDto list

  3. to_pinyin is a method to convert Chinese characters into pinyin, no need to pay attention here

View layer's method of returning Json


  def get(self):
    param = request.args
    id = param['id']
    # 如果id为空,查询的是从根目录开始的各级菜单
    rootMenus = queryByParent(id)
    rootMenuDtos = model_list_2_dto_list(rootMenus,
                       "MenuDto(id='', menu_name='', menu_url='', type='', parent='', subMenus='')")
    # 设置各级子菜单
    for menu in rootMenuDtos:
      menu.name = to_pinyin(menu.menu_name)
      subMenus = queryByParent(menu.id)
      if len(subMenus):
        subMenuDtos = model_list_2_dto_list(subMenus,
                          "MenuDto(id='', menu_name='', menu_url='', type='', parent='', subMenus='')")
        menu.subMenus = set_subMenuDtos(menu.id, subMenuDtos)
      else:
        menu.__delattr__('subMenus')

    menus_json = json.dumps(rootMenuDtos, default=lambda o: o.__dict__, sort_keys=True, allow_nan=false,
                skipkeys=true)
    # 需要转字典,否则返回的字符串会带有“\”
    menus_dict = json_dict(menus_json)
    return fullResponse(menus_dict)
fullResponse

from flask import jsonify


def fullResponse(data='', msg='', code=0):
  if msg == '':
    return jsonify({'code': code, 'data': data})
  elif data == '':
    return jsonify({'code': code, 'msg': msg})
  else:
    return jsonify({'code': code, 'msg': msg, 'data': data})
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Note: The meanings of json and dictionary in python are similar. When json is finally returned to the page, You need to use the json_dict method to convert to dict type first, otherwise the returned string will contain "\"

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